Author Topic: Wet sumping  (Read 2239 times)

Online orabanda

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Re: Wet sumping
« Reply #75 on: 03.07. 2019 15:31 »
Hi John,
That's interesting (and confusing).
Every A10 /A7 bottom end I have dismantled (dozens) has used a (very) light spring, and much lighter than the A65 springs I have subsequently purchased.

Maybe SRM decided to supply the heavier spring for the pre-unit engines because the original didn't work well enough?

Richard

Online RDfella

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Re: Wet sumping
« Reply #76 on: 03.07. 2019 16:07 »
Indeed they are different:- A65 is .945" long x wire thickness of .018",  the A10 .625" long x .012" wire (according to my notes) making the A65 version quite a bit heavier. SRM supplied me the A10 spring when I asked for A65 so they clearly use the same for both engines.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline duTch

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Re: Wet sumping
« Reply #77 on: 03.07. 2019 18:01 »

 
Quote
......Richard,
I have not seen a strong(er) spring for an A65 as in your photo
SRM list the same spring for A10 and A65   *????* *????*

http://www.shop.srmclassicbikes.com/product/oil-pump-spring-a50-a65-a10-anti-drain-valve.....

 Yes very confusing *conf2*..... I bought one of each spring from SRM about 4 or 5 years ago as per pic (the round thing with the 'ole in it is a magnet just to hold the balls), and thought the light one is for A10/7 - same specs as RD's  *dunno*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Online Greybeard

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Re: Wet sumping
« Reply #78 on: 03.07. 2019 22:03 »
I renewed the spring on my engine recently. I'm sure the one I used was the lighter one.

Online Colsbeeza

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Re: Wet sumping
« Reply #79 on: 05.07. 2019 09:49 »
Thanks Richard,
It is raining again today - I measured up the standard system on my 1960 GF motor, and have attached a sketch. The ball has to lift only about 1mm to expose oil to the bush entry passage. Dimensions are the best I could measure by Vernier, so may not be perfect - a bit difficult getting the jaws where I wanted them into the small passages.
I also had a go at calculating the relative pressures of the ball and spring (for my existing spring - I cannot find my new ball and spring, so have to order another one) opposing the static oil pressure from the oil tank when motor is stopped. My old spring was 17.3 mm long, longer than you blokes have reported, so maybe some PO stretched it.! That could be why I have not experienced wet sumping. I measured the wire thickness at 0.015". Attached is also a graph of the result.
Interesting - The spring pressure on the ball seat will take 2.336 psig, ( I assumed the spring material was Hard Drawn MB ASTM A227 - one of the options) and the oil pressure exerted on the other side of the ball is about 2.322 psig. I used a spring calculator I found on the net.
Anyway, you are right that the spring is p--s weak, and barely adequate to hold back the oil.
No doubt BSA went out of their way to ensure the anti-drain system did not reduce oil pressure to the timing side bush.
So maybe the SRM spring is the way to go. Incidentally, I ordered the springs and balls from SRM before doing the calculation, so I do hope they send me the A65 spring. Gary at SRM said they do not make the longer plug, and that they do not modify the A10 system. Gary's reply two days ago quote "This not a mod that we do to standard engines. So the plug is something we cannot supply, have to be carefull, too long and it will block off the oil feed to the main bush, too short and spring will not be long enough to hold against oil pump body. The standard set up is fine as long as ball has a good seating."
I am still Fence-sitting. :-\
Cheers  Colin
Colsbeeza
Australia

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Re: Wet sumping
« Reply #80 on: 05.07. 2019 12:01 »
Col - nice to see someone who knows how to do a proper drawing. Not sure I understand the graph, though. Maybe the imperial / metric units are confusing me. Hate metric anyway - find it error-prone when measuring. Anyway, my calcolations (.4 psi head etc) are that psi the oill exerts is around .015 psi. Doesn't look right to me, but have checked figures.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline Swarfcut

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Re: Wet sumping
« Reply #81 on: 05.07. 2019 13:19 »
Well impressed by the detail and care taken to get these figures. The more I think about the design, the more I am inclined to remove the valve and go for the on/off ignition linked oil tap.

 A10 or A65 layout has the oilway obstructed to a varying degree by the ball, and the spring is always subjected to continuing hot and cold cycles, no wonder they are a bit p**s poor after 50 years in the dark!

 Swarfy.

Online Colsbeeza

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Re: Wet sumping
« Reply #82 on: 05.07. 2019 23:05 »
Did anyone spot the maths error in the Graph.?
I'll replace the graph here - The pressure exerted by the oil is close to 0.5 psi. Logically, a 1metre head of water exerts 10 KPa, or close to 1.45 psig (g for gauge), so 33 cm of oil is about 1/3 of that or about 0.5 psig. - should have used some logic.!!
RDF - your 0.4 psi is spot on - and the units at the bottom are the spring length, which is about 12mm when installed with the ball against the seat. So 12mm length (as close as I could measure) gives a spring force of 0.088 lbf. The diameter of the ball seat is the same as the oil inlet passage diameter 7/32", so X-sectional area is 0.03767 sqins (roughly  *lol*).
Still very little differential pressure to seal the ball (< 2 psi)- depends entirely on bedding the seat well!
Col
Colsbeeza
Australia

Offline duTch

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Re: Wet sumping
« Reply #83 on: 05.07. 2019 23:38 »

  *doh*
Quote
Did anyone spot the maths error in the Graph.? ......... 
  How silly of me....  *pull hair out* 


 I assume you've allowed for that scientific word for friction in the hose and and galleries, and restriction of the pump ? 'n stuff...?  *conf2*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Online Colsbeeza

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Re: Wet sumping
« Reply #84 on: 07.07. 2019 12:18 »
I can feel my chain getting pulled!
Colsbeeza
Australia