Srtaight Cut drops V Standard Helical ?
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thats a good idea rod , how about the hard against hard with a force fed oil supply and another lubrication groove in the face of either the washer or the gear ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I am not convinced that the thrust washer spins against the alloy case in all circumstances.

That the washers are almost always stuck to the gear tells me there is an oil film in there.

That the surface on the transfer case shows sign of contact does not mean this is the full 'rotating contact' surface....

I suspect the washer is indeed spinning with the gear - it is after all sitting on the idler gear shaft, hence would likelly spin up to speed on it.

As the gear is thrust towards the alloy housing, the washer contacts the alloy, which is initially lubricated, then as it wipes away the lubrication the washer speed slows, to somewhere between the speed of the housing (zero!) and the speed of the gear. On higher axial loads, the thrust washer speed would drop right off - likelly close to zero.

The reason I am thinking this is the speed and diameter is pretty high potentially - I just cant see how steel against alloy could live.

As pointed out - the washer is always stuck to the gear - which tells you there is always an oil film there... The alloy surfaces getting 'chewed up' happens though - and I like the idea of trying to prevent this!

Edited by TurboDave16V on 9th Oct, 2008.

BTW - what is the diameter of the idler pin on an A+??
And what is the OD of the thrust bearings?

The A+ I've always known as 7/8" and earliers as 3/4" - whether they were a metric size close to that, who knows, I've always found it strange how some parts are actually metric although known as imperial.....

Can't tell you the OD as my last A+ is now installed - I can go and measure an A though, I have a few buried somewhere.

I assume you want the sizes to work out some loadings ???

Continuing the theory, if the oil film sticking the washer to the idler gear proves it's there, can we make it do all the work and have no relative movement (hence wear) against the alloy ???

Can we achieve it with the current parts, or do we need to improve them ???

Misalignment suggests spherical mounting is the way forward unless point loading in a small area of a plain mounted component is tolerable.

Or am I talking rubbish (again)....

Schrödinger's cat - so which one am I ???

TurboDave said "To expand on a way of preventing 'overfeeding' oil, the simplest way is to basically fill a chamber adjacent to the bearing, and then allow the oil to flow out of the top of the chamber. Result is zero pressure, and sufficient head to keep lubrication in there."

I bought a used SC/CR box, when I opened the package I found these scoops/scuppers which fed oil to the layshaft. Pretty simple.

Edited by scooperman on 9th Oct, 2008.

Would something like this be any good?

It probably needs a bigger bearing but you should get the general idea.

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Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Paul, that seems like an idea worth trying for sure. Not sure if the blue piece is meant to be pressed or welded?

Once 'inside' of the case depth in an idler it is probably pretty easy to machine.

The big thing though, is deciding what bearing to use. The angular contact SKF's can get VERY expensive...

If you could look at other 'cheap by volume' bearings you might be on a better track - eg metro hub ball-bearings, a sierra rear wheel bearing or maybe even the A-series 1st motion bearing which comes with a nice lip for free...


If someone can measure some centre-distances, gear OD's, tooth count, and helix angle, I can probably make a start on working out some real-life loadings.

The blue plate would be secured by some countersunk screws.

The bearing drawn is a 6303N, but a larger 6304N would also fit.

I'll try and get some dimensional data tomorrow.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I like the idea of using the first motion shaft bearing.

Presumably that must be rated to a very similar axial/tipping load. There are no other bearings on that shaft that take any thrust.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Well, it takes thrust, but not much tipping as the shaft is supported on the nose bearing... It might not be so suitable in reality... If you could compare the general diameter of the balls to a catalogue bearing (i assume you are getting them from the SKF interactive catalogue) you'll find somet close.

A+ idler shaft is 25mm

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Maybe I'm out of order, but I think the optimum solution (compromise, whatever) should be based on as little intrusive work as possible.

If we could replace the existing thrust washers on a helical drop with something that requires little to no machining, then that has to be the preferred solution ???

If the understanding is now that the "tipping" is the cause of wear, we either need something that doesn't mind being "tipped" (ie, a bearing that accepts some misalignment despite higher loads in one part) or something that deals with the misalignment.

Calculating the loads (as I foolishly did yesterday) is irrelevant if misalignment is occuring, surely ???

Schrödinger's cat - so which one am I ???

Trouble you'll have is finding a thrust washer happy at a worse case maximum sliding speed up around 18m/sec, or a best case best sliding speed of circa 12.5m/s (assuming 6000rpm idler and a 40mm OD thrust washer)...
Clearely it can be done - something like - as the laygear thrust washers seem to last well and that is overdriven from the engine speed....


BTW
The 'tipping' isn't what generates the wear - it is the 'cause' of the issue, but the "end effect" of this tipping is the axial thrust (becuase the idler is rigid, supported in bearings that allow an axial float, all held inside a (somewhat) rigid housing).
That is the problem ultimately.

Edited by TurboDave16V on 9th Oct, 2008.

Schrödinger's cat - so which one am I ???

Edited by Paul S on 9th Oct, 2008.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Edited by Rod S on 9th Oct, 2008.

Schrödinger's cat - so which one am I ???

Anyone have a first motion shaft bearing to hand. I have a habit of throwing old bearings away.

I just need the main OD, ID and width for starters. OD and width of the lip would be good too.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Yes,

I measured one yestarday while trying to approximate it's load capacity (as it isn't a standard bearing).

Now in front of me again....

OD (without flange) ~67.5
ID ~28.5
W ~19
OD of flange ~70.6

Thickness of flange ~4.0

Not totally accurate but, Paul, it's a LARGE bearing..

Schrödinger's cat - so which one am I ???

Thanks Rod.

That is big.

But I think it will fit, but does not leave much room for a retaining plate.

EDIT: The root of the gear is about 70mm, so that's a non-starter unfortunately.

Edited by Paul S on 9th Oct, 2008.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I have a very nice piece of bushing bronze here in the same diameter as the trusth washers from the idle gear, I am thinking of writing a bit of G code and making a bronze version of the idler thrust washer but this time put a driving peg on it which would lock up agenst the gearbox at some point making the only moving part the idler gear.
taughts on a fag packet

You can guestimate the speed and torque capacity of the laygear thrust washer easilly.

1) work out the max speed it runs at in an A+ box (headset ratio calc). With this, calculate the max torque at the laygear from your desired engine torque. Multiply the laygear torque by a bump factor (aka shock load / safety factor) of 2.0

2) Take a laygear and lay a ruler or block of steel along it. Not take the or a 1st motion gear and roll the headset gear tooth on a piece of paper in a straight line.

3) Get a protractor and measure the angle of the helix relative to the straight line.

4) Guestimate a PCD for the laygear HS gear - OR - for a worse case for the axial load, just use the OD!


5) Use simple math to calculate the force at the 'PCD' of the 1st motion gear for the torque you had calculated at the laygear earlier (remember that radius is half diameter LOL)!

6) Use Trig to calculate the thrust from the helix angle measured earlier, then subtract the (1) WORST helix angle thrust from either 1st or 2nd or 3rd gears (another pitch diameter and helix calc needed for each) - which I assume are all pointing the other direction?



Simple - but I don't have bits in my hand so can't do it!

Edited by TurboDave16V on 9th Oct, 2008.

PaulH - So long as oil can get in, and OUT, your idea 'might' work. Again though - check the max reccomended surface speed for your material.

Schrödinger's cat - so which one am I ???

Fore some reason BS online wont let me in saying my password is increct can anyone tell me the spec of this bronze it is BS1400: 1985: PBI Concast