I'm showing the basic idea I've had for this valve. It uses the tunnel that exists to connect the conical seal to the main timing case oil seal that feeds the big ends. I estimate the tunnel would be best to be enlarged a few millimetres but this is quite a large casting.
Les
Attachments NORTON%20TWIN%20ANTI%20WET%20SUMPING%20VALVE%20IN%20TIMING%20CASE.JPG NoThe Commando MK3 timing co…
The Commando MK3 timing cover uses a piston and is not always successful, it seems to be hit and miss, the AMR/Nortech version uses a ball plus also seals the pump feedside from the scavenge side which is another leak path the valve alone does not fix.
The pump is positive displacement, so anything on the exit side of the pump will receive positive flow regardless of the pressure drop due to the big end pulling at the oil, so the spring does not have to as light as it needs to be when it is on the input side as positive oil pumps do not suck well.
This is the version I am doing which was originally done by Nortech in the US and now done by AMR.
http://atlanticgreen.com/images/oilpumpmod.gif
I checked the pump output port side surface area and compared it to the annulus from a 1/4" ball inside and 8mm hole in the cover and the surface area was greater so it creates no restriction to the oil flow as long as the ball lifts off the seat. The ball does not need to be pressed all the way back past the the oil slot, it only needs to be lifted from the seat and the oil flows around and past it.
Even the AMR/Nortech one has its failures too with wet sumping the result, from previous experiments on valves holding back oil in a Norton tank a steel on steel joint can still leak but a valve in the inlet pipe with a steel ball on a rubber seat will seal (I have used one successfully for 20 years and it never has wet sumped since I fitted it), so by changing the ball to nitrile then it will be pressed against the steel outlet of the pump and I hope that will clear the failures up. I also have bronze and Torlon balls to try if the nitrile fails. The torlon is used in automotive auto gear boxes in non return valves so has a good history of use in pressured oil galleries.
It helps to have a milling machine to do this mod, especially the mod to the oil pump to add the shaft seals.
Thanks for the feedback Ro…
Thanks for the feedback Robert and John.
Robert: I also had thoughts on the pressure available at low revs but realised the pump is still capable of producing very high pressure from virtually any revs if the flow is restricted. It is true that the pressure drops off at low revs but this is because the big ends are bleeding off the flow into them so when the flow rate reduces so does the pressure. This will cause the valve pushed by the spring to begin to close but this will only close to a point where the valve's restriction balances the oil pumps pressure pushing against it. As oil is incompressible, the flow from the pump will flow at the same quantity to the big end and at the same time create a pressure in the feed line sufficient to hold open the valve.... noting this pressure will be slightly higher than the oil pressure measured at the big ends but the big ends will still have the SAME flow rate and pressure as they did before without the valve fitted so no danger at all. As far as cavitation goes, there will be no change to this effect caused by the valve (if there is such a situation) as the valve will be fully open at this high rev point and have no influence.
John...I have to admit to being completely uniformed and in the dark as regards the Mk3 cover (I would however love to see one and how its valve is sited though) I am also completely in the dark as regards any other valve or modification. The thinking behind the idea of my one was driven by the possible easy modification of an existing cover (I realise the timing covers with the internal pressure relief valve would not be able to contain this mod but these are relatively few). The only required cover mod would be to have to enlarge the oil way drilling a little to allow a decent piston diameter to slide in from the end cover bolt (also used for the head lube on Commandos) I can see this idea working wellas long as the seal that is created when the piston is pushed back into the tunnel seals well enough. This would necessitate the oil way tunnel being reamed for smoothness and the piston being a very close fit. However we have about 100PSIpotential pressure at the pump even at low revs as explained above so sticking of the piston in the closed position is never going to be a problem ( I put my head on the block here). As far as testing it, one could use a clapped out engine as this will be in the worst engine state..Eg. lowest oil pressure and fastest wet sumping drain down so improvements will be more noticeable and no worries cost wise on things going wrong and causing damage but as said I'm sure it will work reliably...( yes, I have heard of "famous last words")
If someone had enough time the mod will take only a short time to implement and bench testing could be done quite easily before fitting to an engine...sorry I don't have a lathe myself!
Anyway... it would have been simple for Norton to have included something similar but as you know regular daily use of the bike negates wet sumping anyway which was more likely in those days.
Les
A piston running in a ream…
A piston running in a reamed bore where the oil will not flow until the piston is past the x drilled oilway is an accident waiting to happen. Even a positive displacement pump cannot move a jammed piston or a piston with sludge built up behind it. The link I gave in my post of the A MR/Nortech is already used on hundreds of engines in the US including the Colorado Norton Works bikes, all I have done is some minor improvements, x seals instead of o rings in the pump and softer material balls for better seals.
I appreciate your views Jo…
I appreciate your views John...I will read up about the A MR/Nortech valve....but doesn't the standard Norton Oil Pressure Relief Valve have a sliding piston in a reamed bore....
?....Never heard ever of one of those going wrong.....Les
OOOOOOOOOOOOOOOOOPSSSSSSS.…
OOOOOOOOOOOOOOOOOPSSSSSSS.......
Sorry Everyone.....I just sat down to watch the TV and a very heavy penny dropped with a loud CLANG....My poor old idea is NO GOOD!...
I just can't believe I didn't spot it but there is a very BIG problem.
I was going to tell you but I might as well leave it for you to tell me...So rather than just delete the whole thread there's Browny points for the first person to point out the mistake....
Sorry for wasting anyone's time though....Les...
i don't know Les but this…
i don't know Les but this is my go. is it that the oil pressure relief valve would operate lowering the pressure so the valve wouldn't open to the crank oil feed.
Barry
Hi Barry...I don't think…
Hi Barry...I don't think that situation would arise, but good thinking. The valve spring pressure needs only to be light as it only requires the valve to shut after the motor has stopped so not much pressure is required to push back the piston into the closed or open position.
The problem is more basic than that .....Perhaps I'll say what it is then....
The valve would occupy too much space within the oil seal cavity. I was forgetting how far the crankshaft end enters this and you can see by witness marks on the crankshaft end how far this is and so there is just not enough room to house it there....Oh well, I thought it was a good idea as it could be fitted with little modification of the timing cover....As said in the title, it was a basic idea...well at least I spotted the problem before anyone took up the project, I would not have wanted to waste any more of any ones time.
Thanks again Barry for the guess.
ATB....Les
The only reservations I can think of are , The spring would need to be weak enough to allow for very low pressure when oil very hot at tickover, and apparently there are times when at high revs there is no oil pressure at all but the oil still flows to the big ends as its being sucked through by the centrifuge that thinks its a crank . The oil would still flow but there might be cavitation on the crank side of the NRV that could damage the shells?. As you will be testing it on your old nail , it won't worry us!
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