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Posted: Mon Jul 18, 2011 10:46 pm
by robin.parker
Sorry about that, I had been told that Alpha were no more! wrong it seems.

Posted: Mon Jul 18, 2011 10:48 pm
by john.nash
I spoke to them on the phone.
Very helpful and honest.

I am just balking at the cost.

How long does a big end last in a road application (i.e not flat out all the time)

Posted: Wed Jul 20, 2011 6:07 am
by nevhunter
Depends on the metal used, the heat treatment and the punishment you give it. IF you are revhead brought up on a diet of Honda Benly's, then less than 10,000 miles.. I've seen a well cared for 1939 Red Hunter do a genuine 100,000 miles, but that is an exception as it was ridden gently. When these types of bikes were in regular use and I was rebuilding them, not to restore but just for transport, the mileage of a B33 bottom end was about 30,000. The Ariel would be similar. When I ride on rally's these days I reckon the riders give them a harder time that when they were new. The Hoffman and R&M bigends were well made. The original AJS big end is two piece crankpin, with a sleeve of hard steel and a centre "shaft" of high tensile steel. One piece replacements often break so I don't use them. Alpha have been making crankpin assemblies for a long time. There was a time when the metal used wasn't so good and they changed suppliers. Some pins were breaking in racing situations. This is a fair while ago, so most of those pins should be gone. They're probably OK in normal work anyhow. There is a lot of work in a big end assembly. ( roller type). You have to make sure that the pin is a good fit in the flywheel and the hardened bush is an interference fit in the rod eye, and the bush has to be honed or lapped to a final fit for the rollers. Do Alpha provide a service for this or just supply the parts?. The last Alpha bearing that I fitted had the pin a bit larger on the parts that fit the flywheel. This would be to allow for a bit of oversizing when the engine has been dismantled a few times. By rights each pin should be fitted individually to it's own set of flywheels. This is pretty speciallised work. Nev

Posted: Sat Jul 23, 2011 10:53 am
by admin
As an addendum; I picked what looks like a new polished 500 single conrod, with small end and perfectly fitted bush for £45 at today's autojumble.

What would be the advice ?
Crowded rollers (which I think is that it had originally) or caged rollers. I believe I can get the rollers, at least, separately from Mr Kemp.

Posted: Sun Jul 24, 2011 3:59 am
by nevhunter
John, on 500cc motors that I rev a bit, I have chased around and obtained the original Duralumin(tm). cage. I have never seen one break. When you use crowded rollers, you get more in so that is an advantage, from a load carrying perspective.All the 350's that I have built don't run a cage and I've had no problems with them at all. Try to get the conrod alignment spot-on, I think that is very important, and then I don't run a lot of clearance, because they will hammer out more when they start out with play.. ALL fun isn't it?..... Nev

Re: Any other big end suppliers apart from Alpha ?

Posted: Sun Jul 24, 2011 1:24 pm
by Paul Slootheer
John, a 350 makes quite a lot revs with a uncaged bearing... If you are moderate on the revs you may consider this: I once have had a VB fitted with long, uncaged 1/4 x1/2 rollers from a Harley! This also worked very well. I did quite a few miles and never had any problems whatsoever! The Harley rollers comes in quite a few oversizes and with the mileage you don’t get a ridge in the middle of the pin… ;)

Posted: Sat Aug 13, 2011 6:16 pm
by robin.parker
John. I was looking around on the net for Saddle Springs for my Matchless and came across "British Only Austria" typed Ariel Big End into the search box, yes it's there, a bit dear for my liking, but at least they offer them

Posted: Sat Aug 13, 2011 11:05 pm
by Simon.Gardiner
Uncaged bearings don't like revs (the rollers twist and bind against each other). I never got a 350 big-end to last longer than 7000 miles - although that was using motorway speeds.
The 500 is overgeared so it might be kinder to uncaged bearings...but I can claim to haver broken a duralumin cage (very annoying and expensive as I'd used it to replace the brass cage that the new bearing had come with, and the bearing was wrecked).
Is British Only Austia reselling Alphas?

Posted: Sun Aug 14, 2011 6:09 pm
by robin.parker
I've no idea how we could find out where British Only Austria get their Big Ends, your guess is as good as mine, they certainly are dear enough! The old time gurus would say that, when highly stressed, crowded rollers can skid, which is why we had cages in our 500s and why clever people like Phil Irving (Vincent) used 3 rows of shorter, lighter (caged) rollers with less inertia thus less risk of rollers skidding.
A high compression, high BMEP, high revving and high geared 500 single, is bound to give a Big End a hard time, which is probably why Mr Legge, the Gloucestershire Genius, converted his VHs to plain floating bush big ends, with a pressurised oil feed to the crank, he did other clever things to his Ariels too!