VH-crank - oil supply

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Hermann.Asamer
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Re: VH-crank - oil supply

Postby Hermann.Asamer » Sun Jun 30, 2019 6:59 am

What still worries me is the fact that - based on all your comments - I haven’t found the root cause for my failing bigend.

What i had in was: 1) VH - steel crank, all the oilways were free, it was an old one but got a new cage and repaired
2) 1938 timing cover with the pressure regulator fitted, this was fully screwed in
3) new Morgo pump with the green (later) gasket

4) I had no pressure reading on the gauge but when opening the nuts at the rockers, oil came ( sufficient), as the return worked fine.

my crank became noisy and used up within 10 miles!


I have now fitted an other VH crank, which I had in stock, my concern is now - what to change / check in order not to have the bigend failing within shortly again.

It could also be possible that the first crank was not repaired properly, and that the oiling system had worked fine, but at least I want to make sure that the oiling system works now!

Thank you in advance for your support in my tricky situation !

john.whiting
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Re: VH-crank - oil supply

Postby john.whiting » Sun Jun 30, 2019 7:39 am

After a failure,always thoroughly clean all metallic sediment form the entire oiling system and crankcases......this sometimes takes a bit of doing,because the sharp steel particles tend to lodge in oilways ,and inside the crankcases..........the oil tank and pipes must also be thoroughly cleaned,only done by removing the tank and shaking it out with screws or sharp nuts,and running brushes thru the pipes........you should also check the clearances in the bearing after fitting.......there should be at least .001" clearance......any drag or bind is too tight in a roller ,and will seize.You should also check for bossing of the smallend in the piston........sidethrust here may cause a seizure......first check that the flywheels are centralized in the cases,then check the rod for being central in the crankcase.......these checks with the drive spring retainer nut tightened.

nevhunter
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Re: VH-crank - oil supply

Postby nevhunter » Sun Jun 30, 2019 9:42 am

The biggest cause of a B/E failure is poor workmanship and having odd sized rollers. Your roller should all come from the one box (batch) and still be checked for being the right size to an exact figure. If you have one slightly large one it will take all the load.. You conrod must be checked for twist and alignment and be centred in the cases. It must not be too tight. You need a fit of about 3/4 ers of a thousandth of an inch. there should be no binding or tendency to wind to one end.
It's possible for the dural cage to fail on the VH model, because it's there, but this is not common. If the pin is second hand it may be ready to start pitting . Hard bits flake off it. This can cause it to fail at a low mileage figure as the hard bits muck it all up.. Some people are using the wrong material to make a roller bearing pin and are nitriding it instead of case hardening and grinding it. OK for a plain bearing but not for rollers. Alpha are probably still doing the whole job if you send it there but Max has passed away so check if all's normal there. It's the most critical part of your motor. Normally the VH bottom end is not much of a problem. Nev

Hermann.Asamer
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Re: VH-crank - oil supply

Postby Hermann.Asamer » Sun Jun 30, 2019 12:16 pm

Thanks for the comments, as it’s not my first Ariel
Single I am doing now, I am aware of these things.

As I never had bad experience with the lubricantion system, I haven’t too much familiarized myself with it.

I cleaned the oil pressure valve again, fitted the old version seal and also the original pump.

Now I have got pressure showing on the gauge, almost nothing at Rickover, up to 30 with revs.

The oil is also pumped back to the tank - so everything should be fine - or is there something else to check or a possible failure for not getting the bigend lubricanted ?

Thanks in advance..

nevhunter
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Re: VH-crank - oil supply

Postby nevhunter » Sun Jun 30, 2019 11:57 pm

Cut the oil pressure back. It just loads the pump and reduces the flow. Any pressure (say 5 psi) is enough if the spring is controlling it. IF you have none at tickover the pump must be suspect (OR that later gasket) either worn or loose fit (only needs to be at the actual end of the plunger) or the ball is not seating well There are two types of spring and the square head cover is different with each. One is a light tapered spring and the other is longer and small dia parallel and I don't like the last type although it's easier to install. Nev


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