Stuart Number 9 Engine

[jcreasey]

Part 1 - Flattening the Base​

Today I finally made a start on my No.9 I have had the castings for a few years now but I wanted to finish some other projects before starting it. Also to be honest I am always very nervous about starting a new engine and I have been procrastinating quite a lot!

Here are the castings. They are very old. No sign of the original packaging (they arrived in a wooden box!) but I do have the plans and the book. The plans are dated 1975. Some rust on the fixings but nothing too major. I also have a set of castings for the governor (bought separately) if we get that far. The crankshaft looks to be cast. It includes piston rings and the keyway key for the flywheel.

I decided to start with the base. First cleaning it up with files till it sat flat with no rocking. Then I put it in the surface grinder and made both sides flat and parallel.

I am very lucky to have this wonderful machine in my home shop.

Next came the very tricky part of the sole plate. This is quite difficult to hang on to but I eventually managed to get the bottom to sit flat using my files.
Once that was done I bolted it down to my milling machine and flattened the crosshead ways with a 12mm end mill. Once I had that as a reference surface I could flip it over and bolt it down using a 123 block as a spacer. The photo below shows my clamping arrangement. The casting is supported by the block on the left and the block on the right is just there to provide some bracing using a couple of adjustable parallels as machinists jacks sitting on top of a second 123 block. The rear support for the strap clamp is sitting between the bearings and is supported by the second 123 block also. A bit precarious but it seemed stable enough and I took light cuts to remove all traces of my terrible filing skills! It seemed to work out ok. So far everything is flat and parallel.

Ok that's it for week one. Now I am thinking about how to machine the rest of the sole plate. Right now the current plan is to bolt it down to a hefty lump of aluminium which I will square up. Then I should be able to attack it with the boring bar. Stay tuned for further instalments!

 

[Sprocket]

I have some castings that have been aging for a while too. Maybe not as long as yours, but you really have to let them age .
Doug

 

[trlvn]

Looking good! We'll be cheering from the sidelines!

Craig

 

[peterl95124]

possibly my favorite of all the Stuarts !!!

be very careful with the sole plate and don't make the mistake I made, be sure that the crankshaft bearing mounts are machined so that the cylinder will be centered in its mount at the other end, mine is off by a bit, not enough to be noticeable by the casual observer, but noticeable by me, and in retrospect it could have been off by much more because I was just eye balling the lineup when machining the bearing mounts first without much forethought about the cylinder mount !!!

also, if like mine yours came with a cast-iron cross head, you might want to toss that and make one from bearing bronze, I did because this is a sliding part (and it also looks better).

finally, I made a new crankshaft with tungsten counter weights so the engine doesn't try to walk across the table when its running !

if when you're done you want to pair it up with a scale Edison Bipolar Dynamo let me know and I'll try to figure out how to share my plans.

PS, if you don't want to paint (I'm not a fan of paint) then you can get a great looking and somewhat rust-preventing finish with "naval jelly", its got phosphoric acid in it and creates a phosphate coating that is grey and very durable, in fact its what is in primer paint to improve adhesion.

 

[jcreasey]

possibly my favorite of all the Stuarts !!!

be very careful with the sole plate and don't make the mistake I made, be sure that the crankshaft bearing mounts are machined so that the cylinder will be centered in its mount at the other end, mine is off by a bit, not enough to be noticeable by the casual observer, but noticeable by me, and in retrospect it could have been off by much more because I was just eye balling the lineup when machining the bearing mounts first without much forethought about the cylinder mount !!!

also, if like mine yours came with a cast-iron cross head, you might want to toss that and make one from bearing bronze, I did because this is a sliding part (and it also looks better).

finally, I made a new crankshaft with tungsten counter weights so the engine doesn't try to walk across the table when its running !

if when you're done you want to pair it up with a scale Edison Bipolar Dynamo let me know and I'll try to figure out how to share my plans.

PS, if you don't want to paint (I'm not a fan of paint) then you can get a great looking and somewhat rust-preventing finish with "naval jelly", its got phosphoric acid in it and creates a phosphate coating that is grey and very durable, in fact its what is in primer paint to improve adhesion.

Thanks for the tips. My crosshead casting is bronze so that should be ok.
I made a little PM Research generator for my last steam plant, so I am definitely interested in your Edison plans!
Paint is a long way away right now but I think it will probably be a bit of a shelf queen so I will have to make up my mind on what colour eventually.

 

[jcreasey]

I have some castings that have been aging for a while too. Maybe not as long as yours, but you really have to let them age .
Doug

Unfortunately these things have a nasty habit of outliving their owners.
I'm determined to avoid that if I can!

 

[Steamchick]

I agree with the advice about using phosphoric acid based rust treatment or primer. A necessary rust prevention on all modern cars.... (with steel panels). It forms a resistive molecular thickness coating bonded to the steel, almost eliminating electrolytic corrosion .
But oiling and ķeeoping the models dry, and protected from rapid temperature changes - e.g. wrapped in Oily rags for thermal insulation - does a lot to prevent corrosion.
Nice model. Just make sure (by a single setting?) That the cylinder mounting face alignment is true and perpendicular to the crank bearing axis. As well as the cross-head slide surface.

Cheers!
K2

 

[jcreasey]

Part 2 - The Fixture Plate​

Before I could proceed any further with the sole plate, I needed to bolt it down to a fixture plate so that I would have some repeatable reference surfaces.
Of course before I could bolt it down I would need to drill some holes into it to bolt through.
And of course because I would need to know where those holes were so that I could transfer them I would need to attach my sole plate to some kind of fixture plate.

I believe this is what you would call a 'Catch-22' situation!
Anyway, I decided I could glue my sole plate to a piece of plywood using the old masking tape / super glue trick.
So I neatly covered my plywood with masking tape, being careful not to overlap at any point.
Then I covered my sole plate with masking tape, carefully trimming around the outside edge.
Finally I applied some cyano-acrylate (super glue) to the tape on my sole plate and pressed it down in the centre of my plywood.
I clamped the whole thing down to my mill and then used an assortment of brass aluminium, 1-2-3 blocks and woodworking clamps to give myself something I could align with the X axis on my mill.

Now everything was bolted down I used some rod to eyeball the center point of the mounting lugs on the casting before proceeding to carefully center drill each one whilst carefully noting down the X-Y position of each hole. These would be important for making my real fixture plate later on.
Finally I drilled and reamed each hole 4mm.

Now to make a 'real' fixture plate!

I had planned to use a large piece of aluminium plate which I had on hand. Aluminium does not really grind very well though, so I thought I would splash out and get some gauge plate. So off for a long drive to the local steel merchants and I returned with a life time's supply (for me) of 12mm x 100mm gauge plate, a box full of interesting offcuts, and a big hole in my wallet.

I quickly chopped off a suitable chunk and then spent quite a few hours getting it as square as I could possibly manage.
I first indicated into vertical on the mill and trimmed the ends before cleaning up the ends on the surface grinder.
The squareness comparator showed that I was pretty close to square, being around .001" out.
I decided to correct that and proceeded into the fun of chasing tenths. Eventually I got tired of chasing tenths and decided it was good enough being within 2 tenths of square as far as I could tell with my somewhat questionable surface plate.

I did some measuring to try to get things in the middle and then proceeded to use my saved DRO coordinates to drill and tap 4 holes @ M4.
A test fit with some hex bolts showed everything was in the right place but there was just the slightest hint of play.
I fixed this by quickly machining up some studs with M4 at each and and a snug sliding fit 4mm shaft between.
Bolting that down showed no play whatsoever.
Finally it is time to get this fixture fixed!

That's all for this installement. It would have been nice to have finished with a photo of the finished fixture plate complete with it's 4 little studs. Unfortunately I forgot to do that so please just try to imagine it for now .
Edit: I got a photo from the video I took, so no need to imagine now!
Wow, what a lot of work for a little plate.

 

[Steamchick]

For those not in the know:
I realised my comment " Just make sure (by a single setting?) That the cylinder mounting face alignment is true and perpendicular to the crank bearing axis. As well as the cross-head slide surface." - was a bit vague.
What I did (many years ago so no photos).
I set-up the crank main bearings, having already machined flat faces, threads and fitted material for bearing caps, for drilling and reaming in the drill in a single pass. - This so both sides of the main bearings were truly in alignment. I then used a piece of silver steel (in place of the crankshaft) and mounted the base to sit with the extended ends of the silver steel shaft in a pair of Vee-blocks. This meant the drill spindle was perpendicular to the main bearing alignment. I then used a right-angle plate to fix the base (machined underside) surface to, so the cast face and bore of the cylinder mounting was facing upwards to the drill's Quill. Then I machined the face and bore. ON THIS SAME SETTING - I fitted the cylinder, that had been pre-machined (I used the lathe) on the outside, to mate with the base flange.
So I then had the un-bored cylinder truly aligned to the quill for boring to size, then honing to finish.
My boring bar was a piece of 3/4" dia silver steel held in collets in the quill with a fly-cutter for boring. The drill has a slow hand-feed wheel for vertical milling so my hand-over-hand manual feed was all I needed to control the boring feed speed. (dead slow).
I hope this description gives a better idea of how I did it? Right or wrong it worked for me.
Any better suggestions? - So I can do better next time?
K2

 

[Steamchick]

j: I like your double masking tape idea, but worry about the loss of precision from the "flexibility" - compressibility - of the tape itself? My technique for these settings is to use loctite - a break-free version - between the 2 machined faces. Not tape and super-glue. The loctite cures when clamped so air is excluded from keeping the loctite from curing. (I also use loctite when setting lathe tools to centre height on shims. - The shims and tool glue together nicely with loctite so when removed are still exactly set when replaced in the tool post. If re-ground, the shims can be removed and new shims fitted appropriate to the new tool edge height.).
I should then drill straight through both base casting and base-plate in single passes, ensuring perfect alignment. The drilling should be tapping size, followed by tapping both, afterwards drilling clearance size just in the casting. Done this way, with the gauge-plate base plate sitting on parallels, you will have a more precise set-up than your bit of wood and sticky-tape, IMHO?
But it sounds like your care in preparation and set-up has worked satisfactorily anyway.
Well done.
K2

 

[jcreasey]

Just make sure (by a single setting?) That the cylinder mounting face alignment is true and perpendicular to the crank bearing axis. As well as the cross-head slide surface." - was a bit vague.
What I did (many years ago so no photos).
I set-up the crank main bearings, having already machined flat faces, threads and fitted material for bearing caps, for drilling and reaming in the drill in a single pass. - This so both sides of the main bearings were truly in alignment. I then used a piece of silver steel (in place of the crankshaft) and mounted the base to sit with the extended ends of the silver steel shaft in a pair of Vee-blocks. This meant the drill spindle was perpendicular to the main bearing alignment. I then used a right-angle plate to fix the base (machined underside) surface to, so the cast face and bore of the cylinder mounting was facing upwards to the drill's Quill. Then I machined the face and bore. ON THIS SAME SETTING - I fitted the cylinder, that had been pre-machined (I used the lathe) on the outside, to mate with the base flange.
So I then had the un-bored cylinder truly aligned to the quill for boring to size, then honing to finish.
My boring bar was a piece of 3/4" dia silver steel held in collets in the quill with a fly-cutter for boring. The drill has a slow hand-feed wheel for vertical milling so my hand-over-hand manual feed was all I needed to control the boring feed speed. (dead slow).
I hope this description gives a better idea of how I did it? Right or wrong it worked for me.
Any better suggestions? - So I can do better next time?

Very interesting idea! I should have done the bearings first and used v-blocks to set it up before boring the end flange. Oh well it's too late now. Hopefully my fixture plate idea will be good enough.

 

[Steamchick]

j: If you need your aluminium to be machined flat - Only necessary if the manufactured extrusion isn't perfectly flat anyway - then I should not grind it but use a fly-cutter in the drilling machine. At the high speed required of aluminium but not heavy cuts. All you want is a flat surface.
But when I was a lad, we ground aluminium and cast iron cylinder heads on the same surface grinder, with the same stones. We managed a flat surface (checked on surface table with Engineer's blue) and good finish whatever...
K2

 

[Steamchick]

Very interesting idea! I should have done the bearings first and used v-blocks to set it up before boring the end flange. Oh well it's too late now. Hopefully my fixture plate idea will be good enough.

If the bore is NOT perpendicular to the main bearing alignment you'll have piston wear, high friction, etc...
So perhaps after machining your bearings, you should set-up and re-bore & hone slightly to an oversize, then make the piston to that oversize?

Re: "to drill and tap 4 holes @ M4." (- in the base plate).
Another time, when you want to hold 2 pieces together in a fixture, use precision dowels that fit between the 2 parts. A thread in one part and "dowel" shank in the other is not so precise. 2 dowels on one diagonal is normal. More than 2 dowels should be unnecessary.

j: I suggest that when a bit unsure of how to do a set-up, please ask here and others (better than I!) can give us the right answers.
Hope some of this is useful?
N.B. I am an amateur, but the "professionals" can tell me where I am wrong - so we all do better. I take no offence at good advice! (I have a mate who was a toolmaker who taught me a few things that I had done the wrong way - should have asked before making a gaff!).
K2

 

[jcreasey]

j: If you need your aluminium to be machined flat - Only necessary if the manufactured extrusion isn't perfectly flat anyway - then I should not grind it but use a fly-cutter in the drilling machine. At the high speed required of aluminium but not heavy cuts. All you want is a flat surface.
But when I was a lad, we ground aluminium and cast iron cylinder heads on the same surface grinder, with the same stones. We managed a flat surface (checked on surface table with Engineer's blue) and good finish whatever...
K2

I did try both. I think it would have been fine actually. When I got the gauge plate it's got a thou or two of variation anyway. When I ground the aluminium it loaded up the wheel and I think it caused issues because of galling. Probably a softer wheel would have been better. I don't trust fly cutters as much as an end mill so I tried with a really nice sharp aluminium end mill. It got pretty close. I think it was less than a thou variation all over, so probably would have been better than the plate I bought. Of course I could have ground the plate but by then I just wanted to move forward. I could have even just got a bit of mild steel plate and made my own gauge plate but I wanted to play with some and I thought it would be super useful to have.

 

[jcreasey]

If the bore is NOT perpendicular to the main bearing alignment you'll have piston wear, high friction, etc...
So perhaps after machining your bearings, you should set-up and re-bore & hone slightly to an oversize, then make the piston to that oversize?

Re: "to drill and tap 4 holes @ M4." (- in the base plate).
Another time, when you want to hold 2 pieces together in a fixture, use precision dowels that fit between the 2 parts. A thread in one part and "dowel" shank in the other is not so precise. 2 dowels on one diagonal is normal. More than 2 dowels should be unnecessary.

j: I suggest that when a bit unsure of how to do a set-up, please ask here and others (better than I!) can give us the right answers.
Hope some of this is useful?
N.B. I am an amateur, but the "professionals" can tell me where I am wrong - so we all do better. I take no offence at good advice! (I have a mate who was a toolmaker who taught me a few things that I had done the wrong way - should have asked before making a gaff!).
K2

I thought about dowel pins but I wanted to hold it down in 4 places to be sure it wouldnt lift. I also thought about making only two precision studs but if you are making 2 it's easy enough to make 4. Getting it on there is a bit tricky as it has to be exactly parallel but it worked out ok and there is no sign of any wiggle.

 

[Steamchick]

Glad you managed a good alignment. Just not the "best" as done in industry, 2 dowel alignment, then all the "free" bolts for clamping.
K2

 

[Bob Sorenson]

Going to be watching this build closely.

vr Bob

 

[jcreasey]

Glad you managed a good alignment. Just not the "best" as done in industry, 2 dowel alignment, then all the "free" bolts for clamping.
K2

I appreciate the advice. Thanks for taking the time to comment.

 

[jcreasey]

Part 3 - Boring the Flange​

Now that we have some good reference surfaces we can finally make some impact on the castings.
The first job is to figure out the best way to attach things to the mill.
I have a nice angle plate which I previously ground to be as accurate as I could get it and which is about the perfect size for this job. My first instinct was to bolt it down parallel to the X-axis of my mill. The bolt pattern didn't really work for this so I ended up putting it parallel with the Y-axis. This let me firmly bolt it with two M10 bolts and another two strap clamps for good measure. I used a dial indicator to ensure that it was parallel to my Y-axis. The fixture plate was drilled and tapped for two 10mm studs lining up perfectly with the two slots on my angle plate. All burrs where stoned down and everything was tightened up.

Now I used my brass and aluminium plug to centre the spindle as closely as possible to where I wanted to bore the end flange. This somehow did not look good when I first started cutting so I stopped and tried again. The second attempt was much better! If something looks wrong it's always good to stop and double check things.

My boring bar rubbed at full depth so I had to switch it out for a different one. The drawings do not really specify the size of this hole but it can be inferred indirectly from the width of the gland cover which is 1-5/16th bananas. I did end up with a much better surface finish than the photo below would indicate after changing my tool to avoid some rubbing.

I decided to use an end mill to clean up the flange face despite the advise in the Tubal Cain book which suggests using the boring head to make hundreds of cuts to a set depth adjusting the diameter each time. I don't think that is a very good idea as the surface is never visible and because the boss it mates to has only 1/32" depth it is much more important for it to be level with the mill bed (and rear reference surface) than concentric with the mill spindle. Any errors in nod or tilt of the mill head will be eliminated by using an end mill.

Final operation was to back bore the outside edge of the flange. To do this I used my boring head on the furthest extent I have ever used it. I was expecting disaster but it handled this with no complaints. I closed in with many light cuts and ended up with a nice finish. There were a few small overhangs on the top edge but I removed those by turning the boring head by hand as the base prevented it from fully rotating. This worked very nicely. I see no need to machine the front face of the base as it has no mating parts. My theory is that the casting surface should be preserved wherever possible.

So that is it for part 3. I removed my fixture plate from the mill and tested everything. Squareness is within .001" but I think the end flange should be even better than that when measured against the rear reference surface. Next setup will be to mill out the bearings.

 

[Steamchick]

When I wrote previously, I thought you had done this end flange prior to machining the gauge plate base, and crank main bearings. Thus making the gauge plate was a way to translate the bore/flange machining for the cylinder to make the bearing alignment. I didn't appreciate the gauge plate base was simply a way to make a method of clamping the base casting to the right-angled plate.
I feel you missed the point about my Vee-block idea.
The Principle axis of the engine is the Crankshaft. By "Principle", the axis MUST be identified, and secured by machining very early, so most other critical machining can be taken from this axis.
Of course, to permit repeatable setting-up, the underside of your casting had to be machined first. But that is NOT a running / working surface except for a reference to "other machines"etc. when finally mounted.
The Secondary main working axis is the cylinder-bore axis.
Your odd brass and aluminium insert is a little "weird" (in my head) as you set it into a casting, (Not sure how or where it relates to the casting?) then you precisely aligned this to the Quill axis before boring for the cylinder to mate. I am not sure what all this is really doing...? It seems an Imprecisely fitted bar is being precisely aligned, so the imprecision exists in the machining of the casting?
My sequence (Because that's what I was taught in the 1960s when boring cylinder blocks!).
1: Ensure the underside of the base casting is flat with a reasonable alignment to the CAST bearing and cylinder mounting holes. - This is where an appreciation of Datum alignment is required to understand the castings are NOT perfect and often need compromise, if inadequate machining allowance is not provided. The base grinding set-up is where your brass/aluminium bar could help, but scribe lines on the casting work fine for me. I assume the casting is about right, I.E. plus-or-minus 1/8" from where everything should be. "By eye" marks are better than that, so are adequate to decide where the casting is mounted for the flat underside to be ground. - But you have done all that.
2: From the flat base surface, the bearings can be positioned and machined to form the PRIMARY DYNAMIC datum. This is used to mount the base casting on the precisely set-up angle plate. - But with "freedom" to re-position to the Crank-axis.
3: From this datum, the bore can be set: at Exactly the correct distance for the bore axis to be to align with the Primary dynamic datum. I.E. if the bearings were set at 1.457 INCHES above the flat base underside DATUM, then the bore shall be centred EXACTLY at that same dimension. That will centre the bore on the crankshaft axis.
4: With test bar in the bearings, the test bar can be set in Vee-blocks, and the test bar used to clock to ensure it is exactly perpendicular to the Quill. (In case your Vee-blocks are NOT the same size, muck anywhere, imperfect machine alignment, etc.). THEN the base casting can be securely clamped to the right angled plate surface.

You can still use this alignment to eliminate all the TINY errors that are in-built from the machining of all the components by using this as the set-up for BORING the cylinder. All the other stuff is holding the parts together. This BORING to be perpendicular to the crank axis is the PRECISION that makes a good engine.
Sorry if my explanation is a bit crude - Boring even?
If I am wrong will any experts tell me where I am wrong, as I appreciate life-long toolmakers know best - and my friend and mentor is unfortunately past-it now.
j is doing a really careful job, being precise in setting everything to DTIs, etc. But I "worry" that following the wrong sequence or datum can lead to an "Imprecise" engine that disappoints - and we all want this to be the best he can make.
All is not lost: The final boring to the crank axis is the key.
K2