Machining problem

Gentlemen, Something for you all to ponder, on my Gas engine I have to re-machine the mains as the are worn and they are steel on steel and I want to make Phosphor Bronze Bearings. The problem I've got is that my lathe centre height is to small to mount the engine on, by the way Flywheels are only seven inches Dia, so can't in line bore with home made tool between centres. If I use the mill the boring tool is so long the flexing on the furthest hole will make it in accurate. I have some ideas but would like your input to see if it matches mine.

Thanks all,

Martin P

Reply to
Campingstoveman
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What sort and make of milling machine?

-- Regards,

John Stevenson Nottingham, England.

Reply to
John Stevenson

Is the o'all width beyond the capabilities of a long reamer? BTW. Unknown (poss Bathe) engine I have also has no bearings as such. I thought about trying to mod it to accept bushes but there really wasn't enough meat in the bearing caps. I think that CI is not too bad a bearing material providing it is kept well lubricated.

Reply to
Nick Highfield

Its a good quality 1980's mill/drill I have recently bought of my old company.

Martin P

Reply to
Campingstoveman

Nick, I have enough meat in the bearing caps and I also have to skim the crank shaft so not a problem. A reamer requires a hole first of the correct size, I do have adjustable reamers but you still need a hole.

Martin P

Reply to
Campingstoveman

If you extended the reamer to pilot/locate on the far bearing before reaming the near bearing, that should give you a fair location. Need to change the pilot when you reverse the operation, but it's do-able.

Peter

Reply to
Peter A Forbes

I'd be very wary of using phosphor bronze for this application, it really needs to run on a hardened shaft. Ordinary brass would be quite adequate.

Regards

Philip T-E

Reply to
ClaraNET

I'm probably out of my depth here, but would not opening up the existing mains in stages with adjustable reamer(s) long enough to do both at once, ensure that the bearings remained coaxial? Then all you need is that the bushes be concentric (why not use stock glacier wrapped bushes) and all should be ok.

Reply to
Nick Highfield

Too much like hard work :-)) Glacier bushes do they go small enought for a 10mm dia.

Martin P

Reply to
Campingstoveman

Glacier bushes are available down to 2mm bore with DU liner and 8mm in DX. Wall thickness for 10mm bore is about 1mm (housing sizes are in catalogue). Main problem would be sourcing 2pcs only. RS only sell in sets, maybe try Hayley metals?

Reply to
Nick Highfield

Forget everything I just said! I've just looked at your pics again (pretty little thing isn't it) and I see that the bearing area is smaller diam than the rest of the crankshaft even without cleaning up. So no way to fit a bush, a proper split bearing is clearly required.

Reply to
Nick Highfield

I'm with Philip and very sceptical about the use of phosphor bronze as it needs hardened steel journals - however leaded bronze LB4 aka SAE660 bronze is much a much softer bearing metal and my first choice for bushes and split bearings if whitemetal is not practicable.

In a full blown engineering shop would this be a line boring job??

J

In message , ClaraNET writes

Reply to
John Ambler

Following on from my questions about what makes these old engines last, why should a bearing material need a harder journal than others?

I can remember from my AJS 600 twin being surprised that the swinging arm should be worn more than its bush but never really understood why. I imagine grit becomes embedded in the softer material and then grinds the steel?

Again one of the reasons given for the poor longevity of the 250 BSA starfire engines was the use of white metal bearings, what options were there for increased life roller bearings?

I assume at least with plain metal bearings there was always the option of re surfacing them locally whereas the roller/ball bearing needed a mass produced replacement?

AJH (not so much a collector of vintage machines, more an operator)

Reply to
Andrew Heggie

"Andrew Heggie" wrote (snip)

Ah, the Starfire, how BSA must have rued the day they built it, so many faults - so little power ...

My favourite was the invariably poor fit of the secured-only-by-interference-fit crank pins that would slowly turn in the flywheels and strangling the oil supply - thus creating a very stationary engine indeed ;o))

Regards,

Kim Siddorn

Reply to
J K Siddorn

Thanks Kim for the two contributions so far to my quest: higher mass to damp vibrations and close to "blueprint" tolerances. I still would like a bit of the science of bearings materials though.

I have used hopper cooled listers on sawbenches, petters on peelers, sawbenches and waterpumps (and dumpers) and really never done more than check oil levels.

I also watched the programme on spying equipment this evening (ch4). The drawings of the steam generator for a small steam dynamo (OK this is the realms of hot fog I guess) seemed a lot more sophisticated than a pressure cooker. Also the reminiscences of the engineer seemed to suggest it was a small reciprocating device like a mamod.

AJH

Reply to
Andrew Heggie

"Andrew Heggie" wrote (snip):-

Probably Alco Firefly. See:-

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Reply to
Nick Highfield

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