Help Support Home Model Engine Machinist Forum:
B
Bogstandard
Guest
Dave,
No future for this test bed, my own collection.
There will be a nautical home for it's siblings.
John
No future for this test bed, my own collection.
There will be a nautical home for it's siblings.
John
B
Bogstandard
Guest
Not been able to get in the shop to do any machining, it will most probably be the same tomorrow as well.
But to pass a little time and give you lot something to look at, I went over my plans of the control valve that I used on my piston valve engine and rough sketched it out, converted it to imperial and modified it to control this engine in proportional fwd/rev.
This little unit, by drilling one more hole and swapping over which port goes to what pipe, can be used to control a double acting oscillator or piston valve engine. It has the advantage of being totally sealed, unlike the two crescent types that are normally used, that leak everywhere. It could also be used at a push, like a speed control valve that I fitted to my mill engine. But with a small design change could be made into one that did a perfect job.
Here are the rough sketches I have made. I found a ruler at one point and used it, but I slipped back easily into my bad habits of a 'fag pack' sketches.
This will be all lathe and RT work, and I will show in fine detail how to make one.
-----------------------------------------------------------------------------------------
This sketch shows what the unit will look like, plus a cross section of how it fits together.
Because of the close limits and coupled with the o-ring, a leak free unit should be obtained.
These are the dimensions for the outer case, I will be making mine in metric, but these will work perfectly.
The centre bore is not over critical as the spool will be made to fit. But it must be lapped to give perfect concentricity with no taper in the bore, plus make the bore walls as smooth as possible. I will be trying to get the spool and bore within 0.001". The closer the better.
This has to be the first part to be made, everything else is made to fit this piece.
No assembly holes will be drilled in it until the end caps are made, the reason for this is that they can all be dropped onto the RT table and drilled all exactly the same.
These are self explanatory, and the bit to take notice of is how the o-ring recess is made. The 0.004" squeeze on the ring is what gives the unit its sealing ability.
The spool is not made until the other three bits are finished, and is made to fit.
The two final stages will be to cut the two slots, and then relap to the bore after the pipes have been silver soldered into the outer case.
I haven't shown the control arm because it is a personal preference, so I will be making one before final assembly of all the parts.
So that's your lot for this one. Next time I will be making this little wonder.
John
But to pass a little time and give you lot something to look at, I went over my plans of the control valve that I used on my piston valve engine and rough sketched it out, converted it to imperial and modified it to control this engine in proportional fwd/rev.
This little unit, by drilling one more hole and swapping over which port goes to what pipe, can be used to control a double acting oscillator or piston valve engine. It has the advantage of being totally sealed, unlike the two crescent types that are normally used, that leak everywhere. It could also be used at a push, like a speed control valve that I fitted to my mill engine. But with a small design change could be made into one that did a perfect job.
Here are the rough sketches I have made. I found a ruler at one point and used it, but I slipped back easily into my bad habits of a 'fag pack' sketches.
This will be all lathe and RT work, and I will show in fine detail how to make one.
-----------------------------------------------------------------------------------------
This sketch shows what the unit will look like, plus a cross section of how it fits together.
Because of the close limits and coupled with the o-ring, a leak free unit should be obtained.
These are the dimensions for the outer case, I will be making mine in metric, but these will work perfectly.
The centre bore is not over critical as the spool will be made to fit. But it must be lapped to give perfect concentricity with no taper in the bore, plus make the bore walls as smooth as possible. I will be trying to get the spool and bore within 0.001". The closer the better.
This has to be the first part to be made, everything else is made to fit this piece.
No assembly holes will be drilled in it until the end caps are made, the reason for this is that they can all be dropped onto the RT table and drilled all exactly the same.
These are self explanatory, and the bit to take notice of is how the o-ring recess is made. The 0.004" squeeze on the ring is what gives the unit its sealing ability.
The spool is not made until the other three bits are finished, and is made to fit.
The two final stages will be to cut the two slots, and then relap to the bore after the pipes have been silver soldered into the outer case.
I haven't shown the control arm because it is a personal preference, so I will be making one before final assembly of all the parts.
So that's your lot for this one. Next time I will be making this little wonder.
John
andrewh
Member
- Joined
- Apr 3, 2008
- Messages
- 20
- Reaction score
- 10
John,
I've been following with interest and admiration, and now registered - so I can say so!
As before I like your sketching - it is a great way for me (at least) to visualise and work out waht matters and what could foul.
At school we were required to sketch and draw graphs without rulers - the physics teacher insisted that the world didn't operate to straight lines, and a thin perfectly straight line on a graph was a "claim to spurious accuracy" He may not have been entirely right but one person at least remembers!
So thanks for the sketches - very comprehensible and clear
Hope you are able to machine when you choose
andrew
and no - I havn't dremelled my pockets yet!
I've been following with interest and admiration, and now registered - so I can say so!
As before I like your sketching - it is a great way for me (at least) to visualise and work out waht matters and what could foul.
At school we were required to sketch and draw graphs without rulers - the physics teacher insisted that the world didn't operate to straight lines, and a thin perfectly straight line on a graph was a "claim to spurious accuracy" He may not have been entirely right but one person at least remembers!
So thanks for the sketches - very comprehensible and clear
Hope you are able to machine when you choose
andrew
and no - I havn't dremelled my pockets yet!
B
Bogstandard
Guest
Andrew,
Thank you, and welcome to the home of help.
I would suggest you introduce yourself in the welcome section. Some people might not read this post, so by advertising yourself in there, you will get a warm welcome and people will be able to see who you are.
With regards to sketches, I find that people (myself included) find it easier to visualise how a part should look rather than trying to work it out from 2D drawings. It is also wrong, the way I dimension the sketches rather than doing correct drawings, but what the hell, we are not taking exams here, just trying to pass information across as easily as possible.
John
Thank you, and welcome to the home of help.
I would suggest you introduce yourself in the welcome section. Some people might not read this post, so by advertising yourself in there, you will get a warm welcome and people will be able to see who you are.
With regards to sketches, I find that people (myself included) find it easier to visualise how a part should look rather than trying to work it out from 2D drawings. It is also wrong, the way I dimension the sketches rather than doing correct drawings, but what the hell, we are not taking exams here, just trying to pass information across as easily as possible.
John
B
Bogstandard
Guest
gents,
a bit of bad news i am afraid. this post will have to remain on hold for a while.
i have been having troublw with my hand the last few days and after lunch today, just after i had a skype call from al 'dick dastardly', i have now gone a bit too far and my hand is now numb all over. so effectively making it almost impossible to use machinery. it seems that the muscle build up exercises that i have to do to stop the pain has actually caused more damage to the nerve frm my neck that goes past my shoulder joint.
at least i can surf and answer a few posts by using a one finger left hand technique.
i will have to see if stooping the exercises will allow th return of use.
john
a bit of bad news i am afraid. this post will have to remain on hold for a while.
i have been having troublw with my hand the last few days and after lunch today, just after i had a skype call from al 'dick dastardly', i have now gone a bit too far and my hand is now numb all over. so effectively making it almost impossible to use machinery. it seems that the muscle build up exercises that i have to do to stop the pain has actually caused more damage to the nerve frm my neck that goes past my shoulder joint.
at least i can surf and answer a few posts by using a one finger left hand technique.
i will have to see if stooping the exercises will allow th return of use.
john
zeusrekning
Well-Known Member
- Joined
- Dec 21, 2007
- Messages
- 448
- Reaction score
- 0
First the writers strike, now this. :'(
Just kidding John, give your hand a break and work the mind for a while. I hope it feels better soon.
Tim
Just kidding John, give your hand a break and work the mind for a while. I hope it feels better soon.
Tim
B
Bogstandard
Guest
gents,
many thanks for the well wishes.
i have been suspecting this was going to happen for the last few days. so what i am doing is stopping the exercises and hope that will allow movement again.
i know you all mean for the best, but if you could hold back a bit on the well wishing, so it doesn't clog up the post, i would most appreciate it.
i will get back to it as soon as i am able.
thanks again
john
many thanks for the well wishes.
i have been suspecting this was going to happen for the last few days. so what i am doing is stopping the exercises and hope that will allow movement again.
i know you all mean for the best, but if you could hold back a bit on the well wishing, so it doesn't clog up the post, i would most appreciate it.
i will get back to it as soon as i am able.
thanks again
john
B
Bogstandard
Guest
Today I ended up with a good dose of house fever, I was seeing swarf before the eyes.
So with just two fingers working, I managed to get a couple of hours in the shop.
I have already mentioned before that this little control valve that I am making, is ideal for all sorts of control situations on the little air/steam driven engines we make. So if you need to know how to modify it to suit, don't be afraid to ask.
This post only covers how to make the outside bits, but don't worry, plenty of piccies to look at.
This is the stuff I am going to make it out of. I have a glut of hex, so I am going to get rid of some doing this job. A piece of 5/32" copper annealed pipe, an o-ring (only one needed) and four screws. I have already changed my mind when I was making these bits, and I will be using eight of the little ones like the ones on the engine, you can still make it like shown on the drawing though.
I have taken a lot of pictures because there are some parts that need to be explained in detail.
First off was to face the end of the bar, then turn down to the required diam of 3/4" for a length that I could use to get all three casing pieces out of, plus a little bit. It was then parted off.
I had to improvise this afternoon, I didn't have the strength in my fingers to mount up my RT, so instead I used my square 5c holding block instead, This will do the job admirably as I only want to drill a couple of cross holes.
Using the skinny back stop, the block was pushed back to it, vice tightened and the block tapped down onto a parallel. Using the edge finder the centre of the block was located. The finder was then used on the previously faced end of the bar and the drill chuck was located 5/16" in from the face. Using a centre drill and a 1/8" drill, a hole was put right thru the bar. The block was rotated in the vice by 90 deg., pushed back to the stop and was duly tapped down onto the para. Another 1/8" hole was drilled until it met the other cross drilling in the centre of the bar.
A quick swap over to a 5/32" slot drill and a recess was formed to a depth of 1/8", This is the socket that the copper tube is going to be silver soldered into. The other two ends of holes were given the same treatment.
The collet and bar was then transferred back to the lathe for boring.
You don't have to use a collet chuck, as long as your normal chuck is something like. I will be showing further in the post how to keep everything concentric if using a normal chuck.
A hole was drilled to a depth of 1" and the hole was gently bored to the required diameter of 3/8". A few unmoved settings cuts were carried out, just to make sure tool spring hasn't caused any problems. The reason I didn't cross drill afterwards was so that no burrs were left in the hole, by drilling first, they were automatically cleaned up by the boring process.
I used a piece of bar that was 0.001" under 3/8" diameter to check size. Once it was a close sliding fit, I knew it was near enough.
The faced end was marked up as a datum face, to inadvertently stop me taking any metal off it, and the piece was parted from the bar. It was reversed in the chuck and faced to perfect length.
The main block as far as can be done at the moment.
Back to the left over bit.
It was faced off and a spigot machined on the end, 1/16" high and a nice snug fit in the bored 3/8" hole. It was parted off leaving a bit of extra material for bringing back to correct thickness, This was put to one side until the next piece was finished, then the end was machined to give the required 1/8" thickness.
This is the bit that has to be machined in the correct sequence, otherwise, because of the very tight tolerance on the internal bits, if the concentricity is more than 0.001" out, you will be in deep doodoo.
The operation starteth.
Face off the end.
A spigot 3/8" high and 3/8" wide is machined on the end.
It is then parted off with about 1/4" thickness left for machining.
Now this is where everything is kept concentric.
The just machined spigot is mounted into the chuck, and the thickness of the flange is brought to 3/16" thick. From now on, the part will not be moved in the chuck until it is finished.
A 1/16" high spigot, with a nice tight fit in the bore is machined on the end.
A hole is drilled slightly undersized and followed down with a 5/32" reamer.
The recess for the sealing o-ring has now to be made.
I couldn't find my correct o-rings, so I winged it. I did have some silicon 1/8" bore by 1/16" cross section, 'that will do me' thinks I.
So I stretched it over the required 5/32" rod and measured what the ring ended up at. The measured OD of the ring on the rod was to be the OD of the recess, and the stretched cross section measurement, minus 0.004" compression allowance was the depth for the recess. This was duly made into the end of the piece. This will give slightly more drag, but it won't be noticeable.
This is what it looks like fitted.
Job done.
All the necessary bits are concentric. The outside can take care of itself, it is what is on the inside that matters.
Three of the critical parts made.
This is the rough position it will sit in when mounted onto the engine.
This is a very good exercise in forwards planning. Write down the sequence of machining before starting, and you won't have any surprises.
I have arranged for my mate to come down in the morning and mount up the RT for me, so as long as he doesn't get too many beers down his neck tonight, I stand a chance of getting some more done tomorrow.
John
So with just two fingers working, I managed to get a couple of hours in the shop.
I have already mentioned before that this little control valve that I am making, is ideal for all sorts of control situations on the little air/steam driven engines we make. So if you need to know how to modify it to suit, don't be afraid to ask.
This post only covers how to make the outside bits, but don't worry, plenty of piccies to look at.
This is the stuff I am going to make it out of. I have a glut of hex, so I am going to get rid of some doing this job. A piece of 5/32" copper annealed pipe, an o-ring (only one needed) and four screws. I have already changed my mind when I was making these bits, and I will be using eight of the little ones like the ones on the engine, you can still make it like shown on the drawing though.
I have taken a lot of pictures because there are some parts that need to be explained in detail.
First off was to face the end of the bar, then turn down to the required diam of 3/4" for a length that I could use to get all three casing pieces out of, plus a little bit. It was then parted off.
I had to improvise this afternoon, I didn't have the strength in my fingers to mount up my RT, so instead I used my square 5c holding block instead, This will do the job admirably as I only want to drill a couple of cross holes.
Using the skinny back stop, the block was pushed back to it, vice tightened and the block tapped down onto a parallel. Using the edge finder the centre of the block was located. The finder was then used on the previously faced end of the bar and the drill chuck was located 5/16" in from the face. Using a centre drill and a 1/8" drill, a hole was put right thru the bar. The block was rotated in the vice by 90 deg., pushed back to the stop and was duly tapped down onto the para. Another 1/8" hole was drilled until it met the other cross drilling in the centre of the bar.
A quick swap over to a 5/32" slot drill and a recess was formed to a depth of 1/8", This is the socket that the copper tube is going to be silver soldered into. The other two ends of holes were given the same treatment.
The collet and bar was then transferred back to the lathe for boring.
You don't have to use a collet chuck, as long as your normal chuck is something like. I will be showing further in the post how to keep everything concentric if using a normal chuck.
A hole was drilled to a depth of 1" and the hole was gently bored to the required diameter of 3/8". A few unmoved settings cuts were carried out, just to make sure tool spring hasn't caused any problems. The reason I didn't cross drill afterwards was so that no burrs were left in the hole, by drilling first, they were automatically cleaned up by the boring process.
I used a piece of bar that was 0.001" under 3/8" diameter to check size. Once it was a close sliding fit, I knew it was near enough.
The faced end was marked up as a datum face, to inadvertently stop me taking any metal off it, and the piece was parted from the bar. It was reversed in the chuck and faced to perfect length.
The main block as far as can be done at the moment.
Back to the left over bit.
It was faced off and a spigot machined on the end, 1/16" high and a nice snug fit in the bored 3/8" hole. It was parted off leaving a bit of extra material for bringing back to correct thickness, This was put to one side until the next piece was finished, then the end was machined to give the required 1/8" thickness.
This is the bit that has to be machined in the correct sequence, otherwise, because of the very tight tolerance on the internal bits, if the concentricity is more than 0.001" out, you will be in deep doodoo.
The operation starteth.
Face off the end.
A spigot 3/8" high and 3/8" wide is machined on the end.
It is then parted off with about 1/4" thickness left for machining.
Now this is where everything is kept concentric.
The just machined spigot is mounted into the chuck, and the thickness of the flange is brought to 3/16" thick. From now on, the part will not be moved in the chuck until it is finished.
A 1/16" high spigot, with a nice tight fit in the bore is machined on the end.
A hole is drilled slightly undersized and followed down with a 5/32" reamer.
The recess for the sealing o-ring has now to be made.
I couldn't find my correct o-rings, so I winged it. I did have some silicon 1/8" bore by 1/16" cross section, 'that will do me' thinks I.
So I stretched it over the required 5/32" rod and measured what the ring ended up at. The measured OD of the ring on the rod was to be the OD of the recess, and the stretched cross section measurement, minus 0.004" compression allowance was the depth for the recess. This was duly made into the end of the piece. This will give slightly more drag, but it won't be noticeable.
This is what it looks like fitted.
Job done.
All the necessary bits are concentric. The outside can take care of itself, it is what is on the inside that matters.
Three of the critical parts made.
This is the rough position it will sit in when mounted onto the engine.
This is a very good exercise in forwards planning. Write down the sequence of machining before starting, and you won't have any surprises.
I have arranged for my mate to come down in the morning and mount up the RT for me, so as long as he doesn't get too many beers down his neck tonight, I stand a chance of getting some more done tomorrow.
John
B
Bogstandard
Guest
Got a little bit more done today, not a lot, but it was a very accurate day, so time had to be taken.
I won't bore you with reducing the stock from hex to round, but I will say one thing. This bit of scrap turned out to be a length of my stock ali bronze, but because it had been used as a knocking stick I didn't recognise it at first, but noticed as soon as I started cutting. One thing that it does do is heat up fairly quickly when machining, so because I was being very accurate today, I had to leave it to cool down before measuring, so the job took a lot longer.
I rough cut down to about 2 thou oversize, then very gradually brought it down to size, just so the outer casing was a push fit over it.
You might say that I have a lot of material sticking out of the chuck, but this had to be done to keep concentricity with the 5/32" diameter control rod. This was machined on the end without taking the material out of the chuck. BTW there was no detectable size difference between the end of the sticky out bit and the end near the chuck. That is how your machines should end up after years of tweaking.
Here are the two bits on the end of the rod. I draped a bit of the swarf over it to show how this type of material cuts.
I didn't part it off as usual, I have learned from past mistakes with this stuff. I just rough marked it and cut it off on my bandsaw.
This shows the bits, just as my friend turned up to mount my rotary table, about seven hours late.
Just after this Giles and myself made first contact thru Skype. It is always nice to put a name to a face. But luckily for Giles my video wasn't showing on his screen. Nice flycutter Giles.
Back to the job in hand.
This outer case needs holes drilling lengthways down thru it, at 45 degrees offset from the cross drilled holes that were put in before.
So this is my secret weapon to achieve the setup. A bit of silver steel (drill rod) and a small piece of softwood. The steel really needs to be a fair fit in the cross holes.
The first thing I did was to set my RT to 315 degrees. You will see why later.
The rod was trapped in the cross holes by putting the piece of wood in as shown, not too tight, just enough to hold it, if you wack it in there, it is liable to put a curve in the rod.
This weird assembly was then mounted into the RT chuck, resting on a bit of HSS tool steel, to keep the rod above the tip of the jaws, and it was eyeballed along the rod to get it roughly in line with the table slots. The chuck was nipped up, and the DTI was set up as shown (I suppose you could use an edge finder, but i use my DTI for everything).
The table was moved to run the DTI along the rod, and the position of the piece was 'tweaked' in the jaws, until very little runout was detected along the length.
0.0005" over about 1.5" was close enough for me.
The RT was then rotated to the zero position. This put the part in the chuck with the required 45 degree separation from the cross holes.
Now was the time to centralise the RT to my drill chuck.
Because I had a nice concentric hole thru the piece, I decided to use that to save me some time. I mounted a rod just a tiny bit smaller than the bore into the drill chuck, and the table controls moved until the rod just went nicely into the hole.
By using the above trick, it put me within 0.002" of central, so it was time and energy saved all round.
The table was offset on the y axis by 9/32" (0.281", I memory serves me right) and the four holes were drilled thru the block.
Without moving any table settings, the two end plates had their four holes drilled in each.
Holes thru the main chamber tapped to size, and the whole lot assembled to check for fit.
Rather good.
If you don't blow your own trumpet, no one else will blow it for you.
The next job will be to finish off the inner spool and get a bit of silver soldering done.
My man has been booked for tomorrow to remount the vice. Just hope he is on time.
John
I won't bore you with reducing the stock from hex to round, but I will say one thing. This bit of scrap turned out to be a length of my stock ali bronze, but because it had been used as a knocking stick I didn't recognise it at first, but noticed as soon as I started cutting. One thing that it does do is heat up fairly quickly when machining, so because I was being very accurate today, I had to leave it to cool down before measuring, so the job took a lot longer.
I rough cut down to about 2 thou oversize, then very gradually brought it down to size, just so the outer casing was a push fit over it.
You might say that I have a lot of material sticking out of the chuck, but this had to be done to keep concentricity with the 5/32" diameter control rod. This was machined on the end without taking the material out of the chuck. BTW there was no detectable size difference between the end of the sticky out bit and the end near the chuck. That is how your machines should end up after years of tweaking.
Here are the two bits on the end of the rod. I draped a bit of the swarf over it to show how this type of material cuts.
I didn't part it off as usual, I have learned from past mistakes with this stuff. I just rough marked it and cut it off on my bandsaw.
This shows the bits, just as my friend turned up to mount my rotary table, about seven hours late.
Just after this Giles and myself made first contact thru Skype. It is always nice to put a name to a face. But luckily for Giles my video wasn't showing on his screen. Nice flycutter Giles.
Back to the job in hand.
This outer case needs holes drilling lengthways down thru it, at 45 degrees offset from the cross drilled holes that were put in before.
So this is my secret weapon to achieve the setup. A bit of silver steel (drill rod) and a small piece of softwood. The steel really needs to be a fair fit in the cross holes.
The first thing I did was to set my RT to 315 degrees. You will see why later.
The rod was trapped in the cross holes by putting the piece of wood in as shown, not too tight, just enough to hold it, if you wack it in there, it is liable to put a curve in the rod.
This weird assembly was then mounted into the RT chuck, resting on a bit of HSS tool steel, to keep the rod above the tip of the jaws, and it was eyeballed along the rod to get it roughly in line with the table slots. The chuck was nipped up, and the DTI was set up as shown (I suppose you could use an edge finder, but i use my DTI for everything).
The table was moved to run the DTI along the rod, and the position of the piece was 'tweaked' in the jaws, until very little runout was detected along the length.
0.0005" over about 1.5" was close enough for me.
The RT was then rotated to the zero position. This put the part in the chuck with the required 45 degree separation from the cross holes.
Now was the time to centralise the RT to my drill chuck.
Because I had a nice concentric hole thru the piece, I decided to use that to save me some time. I mounted a rod just a tiny bit smaller than the bore into the drill chuck, and the table controls moved until the rod just went nicely into the hole.
By using the above trick, it put me within 0.002" of central, so it was time and energy saved all round.
The table was offset on the y axis by 9/32" (0.281", I memory serves me right) and the four holes were drilled thru the block.
Without moving any table settings, the two end plates had their four holes drilled in each.
Holes thru the main chamber tapped to size, and the whole lot assembled to check for fit.
Rather good.
If you don't blow your own trumpet, no one else will blow it for you.
The next job will be to finish off the inner spool and get a bit of silver soldering done.
My man has been booked for tomorrow to remount the vice. Just hope he is on time.
John
Powder keg
Well-Known Member
- Joined
- Oct 10, 2007
- Messages
- 1,091
- Reaction score
- 3
Looks great John!
B
Bogstandard
Guest
Thanks for the compliment.
I forgot to mention in the post.
As you already know, I am making this in metric, but actually trying to describe it in imperial for our US cousins. I noticed that I have done a slight miscalculation, ever since making this part. If you go by the sketches I made, and drill the assembly holes with 1/8", even though it will work, you might be better using 3/32" instead, it gives a little more room for bolt head size. If you do use 1/8" you might have to turn the head down in diameter slightly.
John
I forgot to mention in the post.
As you already know, I am making this in metric, but actually trying to describe it in imperial for our US cousins. I noticed that I have done a slight miscalculation, ever since making this part. If you go by the sketches I made, and drill the assembly holes with 1/8", even though it will work, you might be better using 3/32" instead, it gives a little more room for bolt head size. If you do use 1/8" you might have to turn the head down in diameter slightly.
John
B
Bogstandard
Guest
This is the final and monster post on the build. The reason is that it is two posts joined together.
This part deals with the last bit, the control valve, and in fact is the only part on the engine that was made in imperial sizes but still using metric fasteners. One of the main reasons was that my pipework was imperial 5/32" (only a minute difference from metric 4mm) and I thought I may as well make this bit imperial as well, but it does show that parts can be made in different standards and still fit together easily. A clear case of not being perfect, but use what you have in stock and make it how you want.
So this is where I started off. The three parts of the outer casing were bolted together and an overall size obtained.
By going from the sketch, this should have measured 0.875", but I think it is close enough, even temperature or finger pressure can change what the reading is, so I measure three or four times, just to make sure I am within tolerance.
On this one, I faced off the end of the overlength, rough cut spool valve. leaving it about 0.025" overlength. Very gently deburred, mounted into the casing, and some screws put in to clamp it all together.
It was then remeasured to show me how far overlength it really was. This measurement showed that it was 0.026" longer than the inner cavity length.
A very fine facing cut was taken to give me an idea of accuracy, I removed 0.021" which if correct should leave me at 0.880".
This last measurement shows me that I am almost spot on, and now need to do a final cut of 0.007". This will take the spool to internal cylinder length with a 2 thou end float.
This was duly carried out, the o-ring fitted and the unit rebuilt with the spool inside.
This is the assembly. The spindle was turned and a slight drag from the o-ring was felt. Good enough for now.
It was taken apart, yet again, and the spool measured up accurately. A machining program was worked out to put the groove in the centre of the spool length, and to leave a land in the centre of the spool measuring 5/32" wide. This land is used to block the inlet port of 1/8" diameter, plus a dead area of 1/64" either side to make sure of very little internal leakage.
Normally I would have used my RT, but because my vice was fitted, I decided again to use my 5c square block with a back stop. An edge finder was used on the end, and the 1/8" milling cutter put spot on in the centre by using my little calculations.
The cutter was touched on, and the slot cut to the depth shown on my bit of paper.
Once one side was cut, the block was flipped over and repositioned against the back stop. The next slot was then cut. Very careful deburring was carried out, I needed the edges of the slot to remain very sharp to help prevent internal leakage. It doesn't matter about the internal finish of the slot because it is only a transfer port.
This is what the finished spool looks like before reassembly, yet another time.
This is the stage where the control valve and engine are first brought together. A few extra bits had to be made. The first one was a new reverse nozzle. This was because I had forgotten to allow for the mounting of the connection tube diameter, so I designed and made a new one to fit the bill. That is what comes of being a smart a##e and trying to plan too far ahead. The other piece was a small manifold to bring the forwards nozzles together to allow for running off one input tube.
A dry fit of all the machined bits was done, and trial and error tube bending and cutting carried out, and soon all the parts were in their final positions.
Now comes the almost tricky bit. Getting them all stuck together so that they make one big piece. So here comes the dreaded silver soldering.
I have no troubles at all making up assemblies like this. If you can follow how I do it, I can almost guarantee good results. But please try your own methods as you wish.
I made myself a small brazing hearth on my worktop. The pieces were cleaned by a quick rubover with scotchbrite in the areas to be joined. My Tenacity 4a flux was mixed with a few drops of water and a drop of washing up liquid to form a nice creamy paste. The flux was painted onto the cleaned areas, including down the holes, not a lot was used, just enough to coat the joining areas.
For 99% of my silver soldering needs, I use 0.5 mm diameter silverflo wire. Here, I wrapped it around the tubing I was using to form a tight spring shape. This was then snipped along the edge to give small circles of wire. On assembly of the parts, the wire was slipped over the assembled parts and pushed down into position at the joint line, as shown in this pic.
The blowtorch was directed onto the largest part of each assembly, not directly at the silver solder. As the brass parts warmed up the silver solder automatically melted and flowed into the joint thru capillary action. The solder and flux will always flow towards the heat.
You can see from the picture, no big blobs of whatever anywhere, just nice clean fillets of silver solder. The heat was only applied for a few seconds, until the larger parts were just changing to a dull red colour. It all happens very quickly, one thing you should never do is put too much heat into the part.
The control valve was stripped down yet again. The just silver soldered bits were cleaned as before on the areas to be joined, and the assembly was put together, using the firebricks and other bits of metal to hold the assembly in the correct positions. As can be seen, the silver solder and flux was applied just as described before.
This picture shows perfectly where the flame was played onto the largest piece and the colour of that piece just as the solder began to flow, a couple of seconds later the flame was taken away. The part was left for a minute to cool down naturally, then quenched in a bucket of cold water.
This is the assembly just out of the clean cold water quench. It shows how the flux has penetrated and cleaned the necessary areas and the silver solder has flowed perfectly into the joints and formed nice clean fillets. If you look into the bore of the control valve you can see where the flux has penetrated thru. No silver solder was taken into the bore because there was just enough to make the joint, with no unnecessary solder to flow into areas of importance.
This was then dropped into a citric acid pickle bath for half an hour.
Out of the pickle, a quick wash in clean water and it was ready to be cleaned down. No files needed, just a quick wipe over with smooth scotchbrite.
It was then tried for fit on the engine, you have to be careful with assemblies like this. After having a fair amount of heat put into it, you will find that the metal is still rather soft because it is in its annealed state. You have to be careful you don't bend the pipes, as it will soon collapse into a flattened shape.
Because of the flux penetration into the spool cylinder, the spool and cylinder were given a quick lap together using T-Cut. After a good clean down, the final assembly of the control valve took place, and checked for operation. It worked perfectly, no internal or external leaks, and a nice control of pressure flow.
But it did need another bit to be made.
The control valve needed a nice snazzy handle, so I thought, one of my new glass slingshot marbles would make a real cool knob for the top.
So a quick grip in a collet, a bit of clean water for coolant, and the tungsten drill had a 2mm hole wacked into the back end of the marble in no time.
A tiny bit of mill and lathework, a quick threading job and some spit and polish, plus a tiny amount of loctite and the control handle was in position to be tried out.
Once everything had been tried out and found to be operating correctly, the engine was assembled with all the new parts, given a dose of oily rag and put out for a photoshoot.
Here is Butch the Invincible, ready to flex his muscles and charm the onlookers.
The Butch is leaving the building.
Is it really, really, honest and truthfully finished?
Not really. This little engine has a final purpose as a testbed, but that will have to wait for some time in the future when my time allows. The build on this engine has gone way over my time budget, and I am glad to get to this stage.
I do need to do some tacho and runup tests on it and make a vid for display on here. But due to my tacho being affected by fluorescent lighting, making it give spurious readings, all the runs need to be done outside. But no way am I doing it in the rain that has been coming down in bucketfulls all day. Maybe tomorrow.
Questions will now be answered, as I have a few answers ready, now that it is finished.
John
This part deals with the last bit, the control valve, and in fact is the only part on the engine that was made in imperial sizes but still using metric fasteners. One of the main reasons was that my pipework was imperial 5/32" (only a minute difference from metric 4mm) and I thought I may as well make this bit imperial as well, but it does show that parts can be made in different standards and still fit together easily. A clear case of not being perfect, but use what you have in stock and make it how you want.
So this is where I started off. The three parts of the outer casing were bolted together and an overall size obtained.
By going from the sketch, this should have measured 0.875", but I think it is close enough, even temperature or finger pressure can change what the reading is, so I measure three or four times, just to make sure I am within tolerance.
On this one, I faced off the end of the overlength, rough cut spool valve. leaving it about 0.025" overlength. Very gently deburred, mounted into the casing, and some screws put in to clamp it all together.
It was then remeasured to show me how far overlength it really was. This measurement showed that it was 0.026" longer than the inner cavity length.
A very fine facing cut was taken to give me an idea of accuracy, I removed 0.021" which if correct should leave me at 0.880".
This last measurement shows me that I am almost spot on, and now need to do a final cut of 0.007". This will take the spool to internal cylinder length with a 2 thou end float.
This was duly carried out, the o-ring fitted and the unit rebuilt with the spool inside.
This is the assembly. The spindle was turned and a slight drag from the o-ring was felt. Good enough for now.
It was taken apart, yet again, and the spool measured up accurately. A machining program was worked out to put the groove in the centre of the spool length, and to leave a land in the centre of the spool measuring 5/32" wide. This land is used to block the inlet port of 1/8" diameter, plus a dead area of 1/64" either side to make sure of very little internal leakage.
Normally I would have used my RT, but because my vice was fitted, I decided again to use my 5c square block with a back stop. An edge finder was used on the end, and the 1/8" milling cutter put spot on in the centre by using my little calculations.
The cutter was touched on, and the slot cut to the depth shown on my bit of paper.
Once one side was cut, the block was flipped over and repositioned against the back stop. The next slot was then cut. Very careful deburring was carried out, I needed the edges of the slot to remain very sharp to help prevent internal leakage. It doesn't matter about the internal finish of the slot because it is only a transfer port.
This is what the finished spool looks like before reassembly, yet another time.
This is the stage where the control valve and engine are first brought together. A few extra bits had to be made. The first one was a new reverse nozzle. This was because I had forgotten to allow for the mounting of the connection tube diameter, so I designed and made a new one to fit the bill. That is what comes of being a smart a##e and trying to plan too far ahead. The other piece was a small manifold to bring the forwards nozzles together to allow for running off one input tube.
A dry fit of all the machined bits was done, and trial and error tube bending and cutting carried out, and soon all the parts were in their final positions.
Now comes the almost tricky bit. Getting them all stuck together so that they make one big piece. So here comes the dreaded silver soldering.
I have no troubles at all making up assemblies like this. If you can follow how I do it, I can almost guarantee good results. But please try your own methods as you wish.
I made myself a small brazing hearth on my worktop. The pieces were cleaned by a quick rubover with scotchbrite in the areas to be joined. My Tenacity 4a flux was mixed with a few drops of water and a drop of washing up liquid to form a nice creamy paste. The flux was painted onto the cleaned areas, including down the holes, not a lot was used, just enough to coat the joining areas.
For 99% of my silver soldering needs, I use 0.5 mm diameter silverflo wire. Here, I wrapped it around the tubing I was using to form a tight spring shape. This was then snipped along the edge to give small circles of wire. On assembly of the parts, the wire was slipped over the assembled parts and pushed down into position at the joint line, as shown in this pic.
The blowtorch was directed onto the largest part of each assembly, not directly at the silver solder. As the brass parts warmed up the silver solder automatically melted and flowed into the joint thru capillary action. The solder and flux will always flow towards the heat.
You can see from the picture, no big blobs of whatever anywhere, just nice clean fillets of silver solder. The heat was only applied for a few seconds, until the larger parts were just changing to a dull red colour. It all happens very quickly, one thing you should never do is put too much heat into the part.
The control valve was stripped down yet again. The just silver soldered bits were cleaned as before on the areas to be joined, and the assembly was put together, using the firebricks and other bits of metal to hold the assembly in the correct positions. As can be seen, the silver solder and flux was applied just as described before.
This picture shows perfectly where the flame was played onto the largest piece and the colour of that piece just as the solder began to flow, a couple of seconds later the flame was taken away. The part was left for a minute to cool down naturally, then quenched in a bucket of cold water.
This is the assembly just out of the clean cold water quench. It shows how the flux has penetrated and cleaned the necessary areas and the silver solder has flowed perfectly into the joints and formed nice clean fillets. If you look into the bore of the control valve you can see where the flux has penetrated thru. No silver solder was taken into the bore because there was just enough to make the joint, with no unnecessary solder to flow into areas of importance.
This was then dropped into a citric acid pickle bath for half an hour.
Out of the pickle, a quick wash in clean water and it was ready to be cleaned down. No files needed, just a quick wipe over with smooth scotchbrite.
It was then tried for fit on the engine, you have to be careful with assemblies like this. After having a fair amount of heat put into it, you will find that the metal is still rather soft because it is in its annealed state. You have to be careful you don't bend the pipes, as it will soon collapse into a flattened shape.
Because of the flux penetration into the spool cylinder, the spool and cylinder were given a quick lap together using T-Cut. After a good clean down, the final assembly of the control valve took place, and checked for operation. It worked perfectly, no internal or external leaks, and a nice control of pressure flow.
But it did need another bit to be made.
The control valve needed a nice snazzy handle, so I thought, one of my new glass slingshot marbles would make a real cool knob for the top.
So a quick grip in a collet, a bit of clean water for coolant, and the tungsten drill had a 2mm hole wacked into the back end of the marble in no time.
A tiny bit of mill and lathework, a quick threading job and some spit and polish, plus a tiny amount of loctite and the control handle was in position to be tried out.
Once everything had been tried out and found to be operating correctly, the engine was assembled with all the new parts, given a dose of oily rag and put out for a photoshoot.
Here is Butch the Invincible, ready to flex his muscles and charm the onlookers.
The Butch is leaving the building.
Is it really, really, honest and truthfully finished?
Not really. This little engine has a final purpose as a testbed, but that will have to wait for some time in the future when my time allows. The build on this engine has gone way over my time budget, and I am glad to get to this stage.
I do need to do some tacho and runup tests on it and make a vid for display on here. But due to my tacho being affected by fluorescent lighting, making it give spurious readings, all the runs need to be done outside. But no way am I doing it in the rain that has been coming down in bucketfulls all day. Maybe tomorrow.
Questions will now be answered, as I have a few answers ready, now that it is finished.
John
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