Part built Allchin 1.5 inch

Hi All

Could I ask some advice, I've received my boiler back after a year away.

but I've noticed some screws which I expected to be removed but are still there, boiler has passed test with certificate but I'm concerned about the screws as I was promised they would be removed.

I feel sick with disappointment if I'm honest.

thanks in advance

I'm assured its safe by a boiler maker who has been building boilers for 25 years.

The screws were presumably there to hold parts during original silver soldering assembly. As such they merely held the flanges etc in place and take no real part in the boiler's integrity.

Edited By KWIL on 16/08/2019 14:21:52

Hi KWIL

So even though they are brass, there's no risk of an inspector failing the boiler?

Kind regards,

Del

[This posting has been removed]

sorry I just meant it had hydraulic and passed, but a boiler inspector is another level?

Do any of the screws go through into the water space?

Hi Derek, if you plan to operate the tractor in public at a club, who is the boiler inspector at the club? I'd talk to that inspector before doing anything with the screws, or worrying too much about it.

If you are using the tractor only at home and it has passed a hydraulic test, I don't think you have much to worry about. The only remaining concern MIGHT be loss of zinc in the brass screws over time if they are under the water line in the boiler. However this could take years to cause any issue and in many cases never happens - it depends a lot on your local water. If your house faucets don't have punky brass / de-zinc issues your boiler probably won't either.

Just food for thought.

Afternoon all,

could someone advise where you can buy copper shims, I need to fit my steam fittings but need to space them as they won’t screw in and line up.

i can find one size washers but not ones in a different thickness like 0.2mm, 0.3mm etc etc.

any help would be great.

thanks

Derek

Most of the ME suppliers who sell steam fittings will do packs of washers in nixed thicknesses. Reeves do them in various diameters here

Hi Derek, you can also make your own shim washers. One way is to get some small sheets of copper in various thicknesses. Figure out your OD and ID needed. Drill the ID's in the sheet about 1.5 x the OD apart. Cut squares with the ID centred in them with tin snips. Snip the corners to make octagons then snip the corners again to make them roughly round, a bit bigger than the needed OD. Mount all these blanks on a bolt that fits the ID, and use washers and nuts to tighten the stack of blanks. Make the bolt long enough to hold all the blanks and leave a good bit of the thread for chucking in the lathe. Chuck the bolt and stack of blanks in the lathe and turn the OD of the whole stack and the end washers. Dismantle after turning and there's a drawer full of shim washers (and a sad looking set of end washers plus a bolt with iffy chucked threads - no extra charge for the last bit).

PS you can also punch the ID's if you have a hand punch or gasket punch if you'd rather not drill the copper sheets

Edited By Jeff Dayman on 20/08/2019 04:25:10

Many thanks Jeff, so I have another question.

Sorry to keep asking everyone but I'm looking to line up the cylinder on the boiler and have positioned where I think it should be.

however my piston comes out the end of the bore, I've checked the lengths of the piston rod, piston and all seems perfect or near as dam it.

I'm not totally sure how much gap you need to leave each end of the bore, should piston end up a couple of mm in from the end, or go right to the end?

I did know id struggle with this part of the build, if I get one end of the travel correct it seems to hit the cover the other end.

Regards,

Del

You should aim for an equal amount of clearance from the cylinder covers each end when in steam so a little less at the back (chimney end) when setting it cold.

Drawings show cylinder 2.094" long less front cover spigot 0.062 gives 2.031" clear cylinder length

Piston 0.406" long + stroke 1.500" = 1.906"

2.031 - 1.906 = 0.125" divided by 2 gives 0.062" or 1/16" clear from covers at each end.

Therefor when hot piston should be 1/8" in from the chimney end and in 1/16" in from crankshaft end. Doing it cold I would say something like 0.107"  (45 + 62) from chimney end and 0.080" from crankshaft end

Edited By JasonB on 22/08/2019 10:53:08

Excellent explanation Jason, many thanks it should get me much closer than I was.

Regards,

Derek

When setting the chimney end do I need to add the back cover spigot length onto the 1/16th clearance that end? or will the 1/16th clearance take this into account.

sorry for the dumb questions but this part was always going to be hard, and I obviously want to get it correct before drilling holes.

Regards,

Derek

Derek, I'm just going to alter what I posted, got the cover without a spigot the wrong way round.

that's Ok Jason, when I say spigot I mean the 1/16th lip that sits inside the bore on the chimney end cover.

This should make it clearer for cold setting.

Once in steam as the boiler expands the cylinder will move away from the crankshaft so everything moves to the left but the piston does not so the 45thou gap will increase and the 80thou gap will decrease and hopefully end up equal.