ShedBoys' First Engine

[picclock]

Hi Shedboy

Looking very good, be interested to see it running. Re making the valves - If you turn between centres, using a centre in the tailstock leaving the head of the valve unfinished until the final parting off, the work will be much stiffer and easier to machine. If the material is not hardened yet you will likely get a better finish using an HSS tool. After you part off the valve head it can be cleaned up on the grinder if needed.

As a rule of thumb unsupported turning length should be up to 4x the work diameter. This is of course rubbish if you work out that the deflection strength varies with the square of the cross section, but for a rough guide on modeller size stuff its not far out. For very thin stuff it should be less .. .

Many thanks for the informative pictures.

Best Regards

picclock

 

[ShedBoy]

Thanx for the advice picclock. The first valve I did turn with a centre in the tail stock and it snapped on a 0.25 pass. I need to make a tiny point for the live centre. The next two were done in a step turning fashion with 0.15 roughing cuts. I just recieved some HSS tools yesterday evening. I have only ever used inserts before and not much fine work like this. This engine is helping with skill building, it is being built to run but it may not.
Tool grinding rest today I think and then a valve seat cutter.
Brock

 

[picclock]

Hi Shedboy

What metal are you using for the valves ? to snap with only a 10 thou cut is not good. Is the tailstock properly aligned ?.

HSS will make a huge difference here as the edge is much finer and the pressure on the work is far less, I would estimate a 1/3rd or less. You do need to hone up the edges quite often, but you quickly get to tell when the edge is going by the feel and look of the cut. I use a piece of India stone soaked with oil.

If you leave the extra at the end of the valve face, about 6mm thick you can just drill it with a normal centre drill - no special parts needed. Part off at the end of machining and throw away the drilled part.

I'm currently moving my lathe into another room (air conditioned 8) ) but am having to make up the work surfaces. Trouble is I hate woodwork and the dust seems to get into your lungs clothing and everything else (and I'm cutting the timber outside ).

Good luck with the engine.

picclock

 

[ShedBoy]

I am unsure of the material I used. I do know that it is magnetic, very bright, precision ground shaft. I scrapped a photocopier to get the stepper motors from it and there was alot of these shafts and bushes.
Any idea what it would be or is there some way I could test it?
You mention hardening valves is this the same process you use for tooling (harden then temper)?
Would I be better off making the valves out of stainless steel?

I got some HSS and have made a rest I just need to put a gurd around the wheel and bolt it all down so I can use it. I think I will still use my tipped tools for roughing cuts and then finish with HSS. Any thoughts?

 

[steamin]

Hi Shedboy, Looking real good for your first engine. I am guessing you are taking this on by yourself without any mentor around. If so, you are doing a fine job and you have come to the right place to share and get some advice and help. Let me pass a couple of machining tips on to you.
1] Carbide cutting tools require more tool pressure to start and maintain the cut than does high speed steel tool bits. For small delicate items I will always use HSS tool bits with a slight radius on the tip for a smother surface, especially on the final cut. 0.010 to 0.015 of an inch is plenty.
2] When I have to have a long stem such as your valves, I will leave about 0.500" sticking out of the collet. Turn that portion to size and then pull the stock out another 0.500" and turn that portion to size. With a little practice you will be able to bring the tool bit to the first diameter and blend it in with the second diameter you have turned. When you get to the final cut for the second turning, you can put a piece of paper of a known thickness between the tool bit tip and the finished diameter that you want to blend into. As you move the tool bit in the paper will start to drag out of your hand. Then you will have a great indication on how close your tool bit is to the finished diameter.

Another trick is to put some layout die on the finished diameter and when you see a slight ring in the layout die, you know that you are there. A Sharpie marker will do the same thing.

You can use a real fine needle file and then some 400-600 grit sandpaper to blend any blemishes you might see.

The basic idea is to use the stock as a support for you and leave the largest diameters to be turned closest to the collet or chuck. Once you have the stem turned and the angle machined, you can pull the the stock out and cut off your creation. Put the valve stem into the collet and face to size.

Keep up the great work my fellow budding model maker.

I hope I have not confused you because I am starting to confuse myself. I wish we were closer together and I could show you first hand. So much of machining becomes second nature that you really do not think about what you are doing. It just happens, so trying to put procedures into to words is kind of hard for me.

 

[ShedBoy]

I have been giving HSS a go but having used carbides for so long it is hard to slow down. I have realised it is slower everything, speed, feed and cut. I am unsure of the material these valves are made of so I do not know if I have to harden them. I was going to turn some more out of some stainless.
Brock

 

[picclock]

Hi Shedboy
steamin's spot on with that info. The finishes you can get with HSS and a bit of lard are really good, if you want mirror you will have to use fine emery cloth and abrasive paste.

For the diameter you are turning I would think the speed should not be a problem. As a conservative rough guide 50 fpm for normal low carbon type steels, which, assuming you have a work diameter of 1/4", means that for every revolution the tool cuts 3/4" (pi * D). So the speed ought to be (50*12)/0.75 -~ 800rpm. Unless you know the steel you are using its tricky to be accurate, but you could probably double that for most steels.

http://its.fvtc.edu/machshop2/Speeds/RPMcalc.htm gives some examples with a better calculating method.

Try using lard as a cutting lubricant - I've used it a lot and it works really well. Just have a small dish with a bit in and a scrap brush. Microwave it if its too thick. Paint it on before turning, with carbide or HSS.

If you can get the required finish, and harden them with Kasenite or similar then the parts will probably be better than if made of stainless which has some issues.

Best Regards

picclock

 

[metalmad]

Hi brock
good going so far
with the valves I make them out of concrete fixing bolts and turn the 45 dregee angle of the valve near the chuck.
that way u only have the shaft coming out from there
makes it easy :big:
Pete
Ps have a look at my posts Sows Ear /rattler and u will see its much better to have the big end near the chuck.
Pete

 

[ShedBoy]

Well I found a container of small bits and after a mate laughing at me saying I never finish things I have made some progress. It is still going to be touch and go if it runs.

Main frame coming together

The beginning of a cam gear

I made two of these just in case, it has one booboo on it but still useable for this engine

Started to make a crank gear out of some unknown material, big mistake. All was going well until about tooth 13 when some sparks come off the cutter and a split second later she stopped dead and made a orrible noise . After some thought I thinmk the material I grabbed was some caravan sway bar steel which was used for a job for the neighbour's rotary hoe, give me grief then too. One seriously blunt involute cutter was the outcome. Need to sharpen it some how.

Lesson learnt is know what you are cutting.

See you next week.

Brock

 

[ShedBoy]

More work on this hideous thing

Bushed carrier for cam gear

Mounted on a shouldered stub bolted to the main frame

Cam made as described in topsy turvy plans but with ETW centaur measurements. Was easier than I thought

All pressed together interferance fit

Cap to hold it on which will be held with a set screw and will also be a pivot point for the governor arm. Maybe.

Beginnings of a flywheel, taper lock centre. I am starting to think maybe I nee a different cylinder and head.
Thanks for looking in.

Brock

 

[Harold Lee]

My crappy scribble plans got in a picture. Please ignore them.
Brock

Brock - Looking real good!!!! And don't apologize for the scribble.... I adds to the whole build... Keep up the good work.

Harold

 

[ShedBoy]

Thanks for the kind words Harold. Got some more done today

Got the taperlock made for the flywheel just need the tightening bolts and some jacking bolts then I can turn the rest of the flywheel on i a mandrel

Made the cam follower also today, used a small bearing for the roller

Fits in place well and has about 2mm of lift.
Still don't like the look of the cylinder :-\ got a piece of steel kicking around which may come into play.
Thanks for looking in.
Brock

 

[Ken I]

Nice going so far Brock, just signing in to keep up with this tread, I want to see it run.

For what its worth high tensile bolts (hot / cold headed) make a good donor material for valves - especially since the upset grain flows into the head.

Beware work hardening steels - but I think you've found that out already.

Ken

 

[ShedBoy]

Yes I did. Waiting on a new cutter but am going to try sharpening the dead one when I work out how it is done.

Brock

 

[ShedBoy]

Made up a pushe rod for the cam follower and drilled the guide hole

Need to trim that block later after I work out the rocker support mount

I have decided to make another cylinder. This is the splined end from a large drive shaft from a CAT scraper 4140 I am told. Machines nice.

In the 4 jaw to get a flat to mount it. Lots of interupted cuts

Nice and shiny

Marked the centre of the bore and located it in the 4 jaw. Lots more interupted cuts. Had to stop as it was quite noisy at 10pm. More tomorrow then it is back to work. Thanks for looking in
Brock

 

[ShedBoy]

Got some more done on the cylinder

Ended up with a 28mm bore. o.o1mm difference from one end to the other. I think it looks better than the other one.

I cast up some aluminium bar to make a piston, I have read in alot of plans to use cast bar for pistons, don't know why. Thanks for checking in, I will be back in the shed next week as I go off to work tomorrow

Brock

 

[ShedBoy]

Back from work so back to the shed, going to give it a good push this break. Here is the beginning of my porous piston. I really need to sort out my casting I think it was not hot enough or I need to get some flux of some kind, Maybe the oil burner is contaminating the melt. I have some ideas I am going to try.

Looks okay here

I am hoping this is not going to matter much here, can always make another if needed, I have seen worse in running engines

Better from a distance with a squint :big: :big: :big:

While in the tool draw on a totally unrelated mission I come accross my old brake cylinder hone which I forgot I had. As I am going to put a cast Iron ring/s in this engine I thought why not give it a hone to get a nice cross hatch pattern for the ring to bed into. Still got more to do. Finish the piston in the morning and make a start on the conrod and crank disc. Got a mates van sitting in my driveway which also needs to go back together (I hate working on vans with the engine under the seat) and going to see a bloke who is retiring and selling off his complete workshop, has all sorts of stuff and junk.
Thanks for looking in.

Brock

 

[ShedBoy]

Well the bloke who was retiring didn't want to sell anyhting but everything was for sale. Ended up with nothing but a 200km round trip, had a beautiful little shaper there to, oh well back to the dodgy engine.

Inside of piston done

Has a few oil holding pits in it but seals good with a couple of drops of oil just need to cut some rings

Taper lock drilled and tapped for flywheel

Able to turn between on a bit of shaft

Soldered on a crank disc and face it off. I have decided to use a shouldered bolt to hold on the big end so it is easy to keep square

It nows has a crank that turns. Going to make a crank gear in the morning followed by some rings. Thanks for looking in.

Brock

 

[steamer]

I like the flywheel! :bow:

Dave

 

[ShedBoy]

Thanx Dave,I was going to clean the sides up a bit more but it seems like it may ruin the theme I have going here :big: :big: :big:
Brock