lil brother air cooled.

[Roger B]

6 thou is a lot to lap/hone. I finish my cylinders with Acrolaps and diamond paste but that requires an ultrasonic bath for cleaning afterwards.

Is that a model traction engine I see in the background of the first picture?

[Jo]

Let me let you into a secret: You can make the bore slightly under or oversized on a model so long as you remember this when you do the piston and its rings. All you need is a smooth parallel bore  . 

Jo

[miss_emma_jade]

6 thou is a lot to lap/hone. I finish my cylinders with Acrolaps and diamond paste but that requires an ultrasonic bath for cleaning afterwards.

Is that a model traction engine I see in the background of the first picture?

its the kenneth wells engine. theres two steam road engines in my life and thats a couple too many. the other one is my full size fowler roller 16771.

[miss_emma_jade]

thanks everyone for the tips on the bore. ive measured it up , and its belled about 0.0005 each end, but the finish is not terrible. i think ill hone it and try to fix that, and leave it the 5 thou undersize or so. im not going to set it up and rebore 0.005 out of the bore. thanks jason for the great tip on the set up plate. onward i guess, i ordered a bit of 01 guage plate to make a solid crank, so thats probably next. the base has been faced underneath, and the bearing machined on the angle, and the face for the cylinder. theyre about the only jobs previously done that are close to right.

[miss_emma_jade]

so a little more progress on this, crank getting close to done, and ive mounted the base casting onto a aluminium set up plate so to help machining. flywheels have been previously bored oversize by another party, so ill have to find something to bush the centres so i can rebore them.

[Admiral_dk]

I see that you're making progress 

The Crank should work nicely 

Per

[miss_emma_jade]

ok. bored the timing gear to a nice fit on the crank tonight. theres a sliding collar or spool for the govenor that goes between the flywheel and the gear. the drawing says "1 req. STL" thats lots of info probably, but my crank is O1 stress relieved, so idealy what steel should i make the sliding spool from to give me best wear? ive got most stuff from D2 to 12L14 in the right size, probably just another bit of o1 might do? what do people think?

[Jasonb]

I've just used mild steel EN1A (230M07) on all the ones I have done in the past. Don't run mine for hours on end so not seen wear.

[miss_emma_jade]

well, crank in, a fraction tight when all clamped down though, hopefully its just pinch on the bearings, and a couple microns will lap out ok. made the spool from bronze, in the end.

[miss_emma_jade]

messed around for an hr tonight.. got these grease cups on the bearing caps.

[Admiral_dk]

Looks good 

If the Crank still is a bit too tight - then "Time Saver" is very recommended by our US members, as it is an abrasive that deterioates into nothing, after a short time ....

Per       

[miss_emma_jade]

think the tight spot is sorted. I must say I like that timesaver lapping compound too. a scrape though with an adjustable reamer was the answer though, just a tiny scrape.
next thing is this cam.. might call in a cnc favour maybe....

unless i can find an easy way to do it on a manual mill.

[Jasonb]

It's just a case of mounting the blank on a rotary table and machining a flat to each dimension as you index it around each angular step then blend with a file.

[miss_emma_jade]

It's just a case of mounting the blank on a rotary table and machining a flat to each dimension as you index it around each angular step then blend with a file.

i at first thought that to be so, it has some segments though, notably 165 - 195 deg, and 60-90 deg, where doing so would cut of the proceeding or following section too short. maybe they can be machined up to centre, working from the low side out. a lot of filing afterward though.

still thinking.. Emma

[Jasonb]

Ah yes I see what you mean. The other option is to print it out to scale and stick it to the metal as a template, mill what you can and then file the rest

If you were closer I'd CNC it, could do the CAD if you need that.