V-twin engine from scratch - yet another interpretation of how (not) to build a

[sorveltaja]

Progress so far:


Cylinder liners are fitted to place. Cylinder bodies lower parts are to be squared.

Two brass pieces on the front are for heads. Not yet sure, are they thick enough.

[NickG]

Ahh, starting to look like an engine now! 

[gbritnell]

It looks like you're making some good progress on the engine. Could I ask how you're going to operate the valves? I know with a camshaft but where are the cam followers going to go?
George

[NickG]

OHC?

[sorveltaja]

Small addition:


On previous pic there was some extra material on the cylinder bodies, to make the jig drilling easier.

It's now machined off, allowing liners to go to bottom.

One thing I discovered about SS 2172, that the SS doesn't stand for stainless steel, but for 'Swedish standard'.

Anyways it is a low carbon steel, that can be hardened. Sort of tool steel I guess.

Stainless would have been better for liners, as the iron piston doesn't get so easily stuck with it.
When using ethanol as a fuel, ferrous metals tend to gather rust.

[sorveltaja]

Thanks for replies .

George, the whole cam/valves- system is to be made following the Hoglet design. Being the pictures that I've seen about it.

Currently I'm working on construction of the heads and valves also, to make them as simple as possible.

NickG, ohc would be nice, although bit overkill to achieve.

[sorveltaja]

Besides the valves and heads, I made housing for cams/followers:


It's indeed butt-ugly, and I doubt if the gears would mesh correctly with that. Two larger holes are drilled with 10mm(0.393") drill.
I should have done them by boring on the lathe .

Anyway, the 10mm holes are for sliding bearings, that'll hold the camshafts. One possible way to correct the timing gears meshing would be to make slightly eccentric bearings, thus allowing minor adjustments.

[NickG]

Good work S, very interesting build once again. I can't quite see how the gears are working at the moment, what is the small gear on the right hand large one?

Nick

[sorveltaja]

I managed to ruin the small gear, when silver soldering the fastening part to it. Solder flooded to teeth also.

I have set of 0.5 mod gear cutters, so it's time to machine the new gear. Never done that kind of job before, but I'll try it with brass and/or nylon.

I can't quite see how the gears are working at the moment, what is the small gear on the right hand large one?
Nick

Nick, small gear is to be machined off, so that the big gears are similar.

[sorveltaja]

I tested machining the gears from nylon and brass. No luck, since my mill just isn't sturdy enough for that. It makes horrible noise, and screams for more mercy. Diameter of the gear cutter must be too large for it to handle, as usual small end-cutters work lot better.

But anyways, next thing I'll try is broaching the teeth, using that very gear cutter. This time the material is aluminum, being softer than brass, and somewhat more solid, than nylon.

[sorveltaja]

'Broaching' in progress:


Above picture shows also my hi-tech dividing head, that is attached to lathe's chuck.

After all, with these equipments the process is grande tedioso, allowing mighty 0.05mm(0.0019") cut to be taken at a time.

I just might get decent gear as a result. If not, there is a lot of other options to test .

[NickG]

Thanks, I get it now!

Great improvisation in the lathe there. 

Nick

[sorveltaja]

Ruined gear, and the new gear:


Cutter wasn't centered quite right, so new gear looks more like circular saw at the end, than gear. It meshes less than well with bigger gears, but I'll use it anyway. 

Generally, that broaching seems to be a good way to make gears, assuming that the required adjustments are correct.

[sorveltaja]

Cylinder liners after some smoothing:


They both have still some deep scratches and spots, that would take ages to get rid of.

But, I'll trust that the same half-baked bore finish works on this project just fine, as it did on previous one.

In the photo are the piston blanks also, that need to be machined to size.

[NickG]

I agree, a few scratches in the bore isn't going to harm anything, it'll probably wear in quite quickly. Some people go to the nth degree lapping and honing to mirror finishes but I'm yet to see any evidence of the benefit to be honest.

You know it works from previous experience and I do with other engines so why change it, presume there's no luberication system as such so it's not like oil is going to come past the pistons into the combustion chamber.

Nick

[sorveltaja]

'How not to' -act 1:


Both cylinder liners were quite straight, after smoothing. But now, after fitting the pistons, they are badly tapered .

Also, neither pistons are airtight.

I used the same methods as on previous project, to fit the pistons. I suspect, that main reason for failure is different liner material.

Also I wasn't able to get good finish, when boring liners on the lathe.

Using correct size reamer would have been an ideal solution, to ensure, that liners surfaces are straight.

[NickG]

S, that's what happened on my flame gulper when I used a wooden lap with wet & dry abrasive paper wrapped around with. I got a cracking finish but it went out of parallel. The fix was to use an adjustable reamer with plenty of oil which gave an acceptable finish and straightness / parallelism.

Nick

[sorveltaja]

I made grooves to pistons for o-rings. There isn't too much room, so groove's width is only about 1mm(0.039"). Ordinary o-rings are too wide, so I made them out of ptfe. It was really hard to get both piston and o-ring to cylinder. Proper piston ring installing tool would have helped a lot. 

At least pistons are now airtight, although quite stiff. Time will tell, how does ptfe last as an o-rings.   


Two bars are for connecting rods. White ring is ptfe.

[Rob.Wilson]

Hi sorveltaja 

looking good  , great thread .

Cheers Rob

[madjackghengis]

Hi Sorveltaja, it distresses me that you had problems with machining your gears, as I just finished doing one in a piece of nasty cutting stainless that looks about similar in size, although it is American rather than a module pitch.  To get my cutter on center, I put it down on top of the shaft where the gear was to be, touching it off with a cigarette paper to zero it, measured across the shaft and the thickness of the cutter, divided it in two, and used my "digital caliper down feed DRO" to put the cutter on center.  With brass and bronze, as well as aluminium, you want pretty good speed, pretty close to the nominal cutting speed, and no slop at all in the ways, as brass and bronze will "grab" and pull if you let it "climb mill".  Brass and bronze need no lube, but aluminium needs a good lube or it gets sticky and balls up.  On my pinion, total depth was .068 which I cut in .030 twice, and a final cut of .008 for a good finish.  You should be able to cut at least that agressively with the brass or bronze.  The real bugger is always slack somewhere, and if you can keep that out, you generally get a good gear.  mad jack

[sorveltaja]

Mad Jack, thanks for the tips .

Connecting rods so far:


As can be seen, holes aren't quite at the center. But in this project, it's only a cosmetic matter .

Anyways, there is still some excess material to be removed, so that they can be fitted in place.

[NickG]

Nice looking rods S. 

[madjackghengis]

Hi again Sorveltaja,  if I might ask a few questions, I might be able to help with your gear cutting.  For my own, I had to make an arbor for the cutter, making one that fit my largest standard (full depth) R-8 collet for my mill, which was .750, and with a shoulder for the cutter to bear against, so it is out of inch barstock, with the hole of the cutter being seven eighths of an inch, it got turned straight to a rather snug fit for the cutter, with the end of the bar in the tail stock center, a full depth of the thread clearance groove leaving the shoulder for the cutter just ten or fifteen thousandths narrower than the cutter, and a standard seven eighths fourteen thread chased on the lathe, and a round nut bored to the diameter of the thread minus double depth of a sharp "v" thread, and the nut chased with a boring bar till the arbor was a nice snug fit.   With a sharp cutter, you should be able to take a fairly deep first cut, and taking one too shallow sometimes ends up with uneven depths, as the cutter pushes the work instead of cutting it.  If the cutter is not pushing out nice curly clean cut chips, stoning the face of each tooth should sharpen it if it is just a bit worn, and if it is sharp, it ought to take a good .030 cut without a problem on the first pass.  I use a cigarette paper, bring the cutter down to pinch the paper between the cutter and the gear blank, and back off the cutter carefully until I can just barely pull out the paper without tearing, knowing I've got a dead on thousandth of an inch between the two when I'm done.  A caliper across the two while the paper is in place, and divide by two, move the cutter down the half, and you've got your cutter on center.  I've cut splines for a PTO (power take off) for my 1953 tractor using the lathe/shaper method, splines for gear boxes, keyways through gears and pulleys, and while it works, it is slow and tedious.  If you can get the cutter working right, you will be much happier a man I believe.  Gears, drive and driven, should both be out of semi-hard steel with good oiling, or if the driven are brass, the driver should be steel, and have as smooth a finish as possible, for minimum wear.  Aluminum is perhaps the worst material for gears that have any real load on them, and particularly bad for gears with a variable load such as valve gearing.  I don't know about where you're at, but here, I often use shafts taken from junk washing machines as they are stainless steel, but definitely good quality, because they don't get twisted up when the washer changes cycles, as they would if they were junk metal.  They will cut cleanly with high speed steel.  I hope this helps if even a little bit.  mad jack

[sorveltaja]

Cylinder head blanks in place:


Also connecting rods are in place. I did some run-in on the lathe with cylinders and pistons installed. Pistons are still bit stiff, but getting better.

Mad jack, good points. But there is seriously weak spot in my mill/drill construction. Being that the two pieces, which support the mill/drill head, are made of aluminum. So it is quite useless for steel milling.

Even on alu and brass, only light cuts can be taken.

That's the reason, why I preferably machine parts using lathe, as much as possible.

[sorveltaja]

State of the art rocker pedestals:


At first I was going to make pedestals, that would be fastened with two screws, but as lazy as I am, looked for something easier, and simpler way.

Solution: use one bigger screw, instead of two smaller .