Industrial oil pump drive disc

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Bill Sargent
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Industrial oil pump drive disc

#1 Post by Bill Sargent »

I noticed in the research section of the site someone posted a question on the industrial motor part that is meant to eliminate the oil pump shaft tang wear in the cam drive slot. The part is a disc that fits in the end of the cam shaft with a raised ridge that goes into the oil pump drive slot on the cam. On the other side of the disc, at 90 degrees to the ridge on the other side, is a slot that the tang on the oil pump gear shaft fits into. The oil pump gear shaft must be shortened to use this part. Photos below show the part and how it is installed. The wear disc part can be installed on any pushrod motor, not just industrial motors. The disc and shorter shaft/gear shown are NOS parts purchased from Gerry McCarthy (not for sale - already in my motor).
Industrial oil pump drive disc together with stock (longer) oil pump gear and shortened shaft and gear for use with the spacer.
Industrial oil pump drive disc together with stock (longer) oil pump gear and shortened shaft and gear for use with the spacer.
Industrial oil pump drive.JPG (61.57 KiB) Viewed 3250 times
Industrial oil pump wear disc installed
Industrial oil pump wear disc installed
Industrial oil pump drive 2.JPG (90.64 KiB) Viewed 3250 times
According to Gerry, the part was introduced on industrial motors so that the tang on the oil pump drive gear shaft did not wear the slot on the cam. The wear is instead on the disc, which could be replaced by removing the 3rd piece and did not require disassembly of the entire motor to repair or replace the cam.

Mike Smith with PRS in the UK has reproduced the disc and sells the disc with a shortened oil pump drive shaft. I believe Mike can also take your shaft with worn tang, shorten it, grind a new tang and harden it, thus reducing the cost compared with purchasing a new shaft (to repeat the wear exercise again).
Regards,

Bill Sargent
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John Clarke
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Re: Industrial oil pump drive disc

#2 Post by John Clarke »

Yes Bill,
This is a coupling used in industry. Can't think of its name. The thing that put me off installing it are the changes that you have to make to the oil pump gear drive shaft. Also, why did Porsche only use them on the industrial engine which normally only operates at lower consistent revs?
Regards Jay
 

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Re: Industrial oil pump drive disc

#3 Post by David Jones »

John, just my opinion but industrial engines like aircraft engines operate sometimes for many hours in total between tear downs and they run at constant speed sometimes for many hours. I would guess that some maintenance aspect because of the kind of use is the reason for the disc being a required part on these engines.
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
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Mike Smith
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Re: Industrial oil pump drive disc

#4 Post by Mike Smith »

Comment by Jay - This is a coupling used in industry. Can't think of its name. The thing that put me off installing it, are the changes that you have to make to the oil pump gear drive shaft.
Everybody is correct
In the UK, it was Barry Curtis who first stumbled over them in Industrial motors - he thought it was a good idea and subsequently always used them on all the race engines that he built
He built a considerable number and was the man to go to back-in-the-day (we lost him to cancer in 2014)

The quickest Race 356 currently running in Europe is piloted by Bill Stephens and his son Will. Bill has always used the coupling dating back to the Barry days

It was certainly a Porsche Part but we have never been able to locate a Part Number for them - the correct name for them is an `Oldham Coupling`

We have continued the practice of using them on special engines via my sons company http://www.prs356.com and have never had a failure. They are manufactured for us by a small Premier Engineering company who only produce quality engineering products

The driven oil pump gear has to be cut back and the tang re-ground, therefore unless a customer needs or requires a new oil pump gear, we supply these on an exchange basis only.
The majority of gears are an interference fit on the shaft (although some are keyed)

NOTE - The work is carried out WITHOUT removing the gear from the shaft
Mike Smith (Essex - UK)

Dick Weiss
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Re: Industrial oil pump drive disc

#5 Post by Dick Weiss »

I just refinish the tang (if not worn excessively) w/a 15 degree angle--the hardness still exists; Otherwise, just the shaft can be replaced
but I still add the angle so the cam's slot won't be damaged by the tang's sharp edges.

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Re: Industrial oil pump drive disc

#6 Post by Mike Smith »

The other benefit of the Oldham Coupling is that it is self-aligning, so you have actually introduced a Universal Joint when you use one
Mike Smith (Essex - UK)

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Re: Industrial oil pump drive disc

#7 Post by Dick Weiss »

Secondary wear(?)

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Re: Industrial oil pump drive disc

#8 Post by Ron LaDow »

Dick Weiss wrote:Secondary wear(?)
Not seeing any, Dick. The cam slot is now engaged over the entire length by the coupling's radiused 'tang', so the wear is reduced by at least (don't have one to measure right here) 50%. The new slot for the oil pump tang captures the tang to the total length for the entire width, reducing the wear there by spreading the loads.
Wish I'd'a thunk of it...
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Re: Industrial oil pump drive disc

#9 Post by DonCichocki »

+1, great product!

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Al Zim
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Re: Industrial oil pump drive disc

#10 Post by Al Zim »

Only once in my life have I seen an oil pump tang wear out. If this concerns you, have the tang lengthened with a couple passes from a heli-arc. when assembling you will have to make sure that the tang in not too long and the gear is proud of the third piece. Knowing how little these cars are driven, there is probably no need to ever worry. In a race car the engine should be looked at regularly long before wear occurs. A point that no one seem to have addressed is if the tang on the oil pump is worn our than the camshaft is worn out and so are the lifters. al zim
Last edited by Al Zim on Mon Aug 05, 2019 8:30 am, edited 1 time in total.
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Re: Industrial oil pump drive disc

#11 Post by Harlan Halsey »

+1 Just repair it by welding and shaping or replace it and move on. No need to festoon the engine with FF filters or anything else.

The slot in the hard cam is wider than the tang, so when brand new there is line contact. Of course the tang wears. The more it wears the wider the contact area, and the slower it wears. That process used to be called "wearing in", hence the "break in" period for new cars.

Oldham couplers are used where two shafts are or can be misaligned, as in the Carrera Vee drives, or in tachometer drive installations on English Ford derived racing engines. The 356 3rd piece is doweled in place to align the oil pump shaft with the cam shaft, so no need for a fancy coupling here.

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Re: Industrial oil pump drive disc

#12 Post by Dick Weiss »

I repair/rebuild all the pump parts--including the spacer/bushing between the pump gear and the
spiral gear on the end of the shaft to suit the 3rd piece such as the end-play of the gear shafts and
re-dress the drive shaft's tang. Also, I have an early large keyed gear shaft for the keyed pump gear.
I even make thinner pump cover gaskets to suit the end-play specs that the regular .008"-.0010" OEM
gaskets are too thick.

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