Author Topic: A10 Wet Sumping - other fixes ?.  (Read 23006 times)

Online orabanda

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Re: A10 Wet Sumping - other fixes ?.
« Reply #90 on: 09.09. 2013 10:29 »
Me too; I share the concerns about the A65 ball arrangement; I don't like what I have measured!. Don’t forget that the ball will have pressure UNDER it at the same time that oil is flowing partially around it.

I am wondering if the throttling effect of the A65 ball arrangement has contributed to some of the crank shaft failures they tend to have. I am not happy with it as BSA have done it, and have in mind  a simple mod to the A65 arrangement.

I have also measured the arrangements for the A10, and the A65 anti-siphon ball arrangement, and have nearly completed drawing both arrangements in Solidworks, which is a 3D modelling program we use for mechanical design (including fluid power manifold blocks).  

I have nearly completed machining a Perspex block, which I will test the A10 pump on, with the A65 arrangement beneath it. I will be measuring pressure upstream and downstream of the ball, and changing the depth of the hole, to work out what depth and spring combination works best. I have also included a cavity to accept an A10 relief valve.

When I have proved the best arrangement, I will publish on the forum.

I will also be using compressed air blown in at a reduced (regulated) pressure not exceeding 50 psi, introduced via a modified oil relief valve, to enable this to be done whilst the engine is together. I will provide details for a jig, so the hole can be drilled square, and to the correct depth.

Pressurising the crankshaft / bearing arrangement like this will also give a visual of leakage between the journal / bearing, and the bearing / crankcase half, which will shock people; an over looked area of leakage.  I discovered this many years ago when blowing air into the oil delivery gallery to an engine (just remove the oil pump to do this). There was as much air leaking from around the outside of the timing bush, as from between the crankshaft and the (worn) bore of the bush! Most the A10 engines I have checked have elongated bores for the timing bush; It typically takes 0.012" - 0.015" machining to clean the bore up. I believe this is because of the stresses (crankshaft flex; there is no middle support bearing) the crankcase is subjected to with high mileage engines,  increased CR, 18 year olds revving the Be Jesus out of them, etc.

Therefore, after the hole is bored true (cleaned up) and an oversize bush (0.002" interference) is shrunk in, it can be line bored, and oil leakage around the outside of the bush is eliminated. A solid phosphor bronze bush is best, as its coefficient of expansion is closer to the expansion rate of the aluminium crankcase, than a steel-backed bush is. Therefore you are more likely to prevent leakage between the bush / crankcase when it is hot.

Any damage to the crankcase timing bush bore (scratches, "tramlines") must be avoided, as this will be a permanent oil leakage path. This can (will) be caused by removal and fitting bushes to a cold crankcase.


Richard




Online RichardL

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Re: A10 Wet Sumping - other fixes ?.
« Reply #91 on: 09.09. 2013 14:16 »
I suppose Richard and others already know this, but I was wondering about the position of the ball relative to the main gallery with engine off,  then,  engine running. It seems that, when off,  it might rest just upstream of the gallery, then, move past  and out of the way when running. By moving the ball against the pump,  is it possible that the ball might align with the gallery when running and "dance"  over to block the way,  due to taking the path of least resistance? Maybe the distance to the gallery precludes the ball moving that far, leaving the clearance around the ball as the only path.

Richard,  is the idea of measuring pressure on both sides of the ball to establish actual pressure on the ball and,  hence,  spring requirements?

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline marathonpaul

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Re: A10 Wet Sumping - other fixes ?.
« Reply #92 on: 09.09. 2013 17:00 »
Very interesting information from all involved. Thanks.

I'm very interested in the results, and already have a recovery plan to reinsert the original spring and ball after pushing in a small sleeve to recover the drilled out material if needed. Meanwhile, no problems and no wet sumping to this point in time.

Paul
63 RGS
58 DBD
38 R71
29 R52

Online chaterlea25

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Re: A10 Wet Sumping - other fixes ?.
« Reply #93 on: 09.09. 2013 18:21 »
HI All,
I know somewhere here on the forum I commented on this topic before, with some photos of the SRM modification
I have another modified engine awaiting reassembly so I took a few more pics and  a few measurements

Depth of hole = 22-23 mm (depth gauge broken *sad2*)
Dia of hole =5/16th in.
ball dia = 1/4in
A65 spring length 24-25mm

My own SR has had this mod and has done 20k + miles and other engines I have built have had no issues with the mod,
I'm not sure about fitting more than one spring, I think they will twist together and shorten???
A plug could be fitted to the bottom of the drilled hole if neccessary to give the proper spring tension
I dont have an unmodified case to measure the depth to the old grub screw fitted from the inside of the crankcase

HTH
John


1961 Super Rocket
1963 RGS (ongoing)

Offline bikerboy

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Re: A10 Wet Sumping - other fixes ?.
« Reply #94 on: 09.09. 2013 20:16 »
John

That's interesting information is the spring a standard A65 spring ?

Offline marathonpaul

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Re: A10 Wet Sumping - other fixes ?.
« Reply #95 on: 10.09. 2013 00:10 »
The spring I got was 26mm (part of an A65 "kit" that had a ball and spring), and I used 15mm of the second spring. The protrusion was 5mm (which looks a couple of mm longer than John shows above)

Paul


63 RGS
58 DBD
38 R71
29 R52

Online Brian

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Re: A10 Wet Sumping - other fixes ?.
« Reply #96 on: 10.09. 2013 01:24 »
Right, the first one of you lot to throw dispersions on my technical drawing skills look out, I will be around to kick your dunny over, while you are in it.  *eek*

I admit if I had done tech drawing at school I would have come bottom of the class but I'm hoping you can understand my scribble enough to get a better idea of what we are all talking about here.

At the top of the first picture I have attempted to show how the original design works, you will (hopefully) see that when the engine is running the ball is pushed back out of the way allowing full flow of oil to the timing bush. The lower drawing of the first picture shows the current proposed modification where the oil has to go around the outside of the ball and then through the coils of the spring to make its way to the gallery. One problem with this is the hole the ball sits in must be larger in diameter to let the oil pass around the outer diameter of the ball. This means when the motor is running the ball will be pushed back and most probably to one side or even may float (dance?) around inside the hole. Another possibility is the spring could fully compress and block the oil flow.

I've added a second picture showing what I think is the only viable way to make this modification work, basically the same as the original design in operation but allowing the ball to sit at the back of the pump so it can be accessed.

Offline bikerboy

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Re: A10 Wet Sumping - other fixes ?.
« Reply #97 on: 10.09. 2013 01:53 »
Without meaning to throw water on somebodies fire if you are going to all that trouble you obviously have the bike stripped down. If its stripped down why not just clean it up replace the parts and use the original system ?

Online Brian

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Re: A10 Wet Sumping - other fixes ?.
« Reply #98 on: 10.09. 2013 02:23 »
I agree bikerboy.

Personally I dont think any modification is necessary.

The point of the proposed modification in this topic is so you can remove and clean the ball and spring without dismantling the engine.

I dont think wet sumping is such a serious problem is requires risking a oil system failure by modifying the original system. I have drain plugs in the sump plates of my bikes, if the bike has sat for a month or more it only takes a few minutes to drain the oil and put it back in the tank.

If I was going to make any changes to this part of one of my engines I would go about it quite differently.

If I lived in a climate where the bike was to be layed up for a few months over winter or for some other reason I knew I wouldnt be riding it for a few months I would simply drain the oil tank.

Offline marathonpaul

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Re: A10 Wet Sumping - other fixes ?.
« Reply #99 on: 10.09. 2013 02:27 »
Nice drawings, and they make some good points. Has anyone charted out the same diagram for the A65? If BSA put the ball behind the pump for the A65, did they change any other aspect of the oil flow?


Paul
63 RGS
58 DBD
38 R71
29 R52

Online orabanda

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Re: A10 Wet Sumping - other fixes ?.
« Reply #100 on: 10.09. 2013 04:39 »
I have been too busy to finish this project off, but will soon.
Anyway, I am attaching a snapshot of my to-scale drawing which has a standard  A50 non return valve arrangement (measured from my 1969 engine), and the A10 arrangement beside it.

Note with the A10 configuration, I have drawn an adjustable seat (threaded on the OD). However, it is positioned to the correct depth for the standard A10 crankcase.

Both arrangement has the spring fully compressed; this reveals the maximum distance the ball will move away from the oil gallery (drilling) through to the bushing.

Note how restrictive the standard A50 arrangement is. Also consider how the restriction can be reduced, if metal from the top of the cross drilling is removed / relieved, or an angled intersecting hole is drilled from the open oil delivery hole.

The A10 arrangement never works well; the spring is too light and long; however IT DOES NOT RESTRICT OIL FLOW TO THE BEARING as it moves fully below the hole.

The A50 always restricts the oil flow to the bearing significantly, but exerts more seating pressure against the oil pump (base).

I have a plan to make the mod successful, but need more time to get back to it, and will test (and measure) the results on a pump test jig, before altering my engines.

When I have more time, I will post a better (clearer) presentation.

Richard

ps have added a side view which shows more clearly the design of the unit engine arrangement.

Online Brian

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Re: A10 Wet Sumping - other fixes ?.
« Reply #101 on: 10.09. 2013 05:14 »
Brilliant Richard, makes my drawings look silly.

By what I can see we are thinking along very similar lines, if the gallery to the bush on the A65 set up was further forward or relieved as you say it would allow much better supply of oil to the bush.

I was also thinking along the lines of a screw in insert so the basics of the original design could be kept, I had thoughts of the insert having a neoprene seat or some other material for the ball to seat against rather than metal to metal.

I was also wondering what sort of pressure is applied to the ball in the original design when the motor is sitting stationary, there is about 3 litres of oil plus the surface pressure on that oil, is the small original spring able to hold that pressure back, maybe not ? If the pump was absolutely perfect it should block the oil from getting to the ball when the motor is stopped but in reality with a gear pump there is always going to be some leakage and I am thinking ultimately the pressure will equalise on both sides of the gears there by applying "head" pressure to the ball.

When you get your test rig going maybe you will find it could be possible to have a slightly stronger spring behind the ball.

As I said before I dont find wet sumping that big a issue but it would be nice to be able to leave a bike sit for a couple of months and know the oil will stay in the tank.

Online orabanda

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Re: A10 Wet Sumping - other fixes ?.
« Reply #102 on: 10.09. 2013 05:34 »
Brian,
The spring pressure standard arrangement is only 1 - 2 psi; however I have calculated head pressure from the tank, and head pressure is less than that.

Yes, my replacement system will be adjustable; at least so I can establish on the rig what the final hole depth needs to be.

So the best arrangement is one where the ball will not obstruct the hole; it will move at least half way past the cross drilling. This means the hole needs to be deeper, and the spring heavier. Note that we should avoid being too heavy as this is creating additional back pressure at the pump, which is why I am duplicating the A10 pump / relief valve system.

3 months ago I fitted the latest version of the SRM pump (now with an internal seal to reduce leakage across the gears getting out through the spindle) and have had the sump and sidecover off the bike all that time.

The leakage has been SFA; maybe 30 ml so I am happy with that. Once the non return valve is sorted, the only leakage will be what comes back from within the crankshaft drillings / galleries, and what is in the return line to the tank. The tank return oil will only leak back, if the anti-siphon valve is not doing its job.

Richard

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Re: A10 Wet Sumping - other fixes ?.
« Reply #103 on: 10.09. 2013 05:45 »
I cant wait until you get your test rig going Richard, should be very interesting.

I would like to step back for a moment though and go back to what marathonpaul was proposing, to simply fit a ball and spring behind the pump.

I would strongly advise against doing this, I think the restriction to the oil flow could be disasterous.

Online orabanda

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Re: A10 Wet Sumping - other fixes ?.
« Reply #104 on: 10.09. 2013 05:46 »
Brian,
Me too; that's why I haven't copied it.
Richard