Drive Shaft Yokes

[Hawke]

I've had to replace the drive shaft yokes on my 1973 Hawke Formula Ford. Unfortunately, I cannot find the original yokes, or similar castings, so I've had to get some weld on yokes from Hardy Spicer, and machine them to suit.

Unfortunately, these yokes are a little thinner, and the spline edges are very close to the outside of the casting. Indeed, a previous one cracked in service.

I'm thinking of just grinding out the real thin part, so to totally eliminate potential cracking. What do the experts think?

Original on left, cracked one in the middle, and just machined on the right.

 

[matt_i]

I'm thinking of just grinding out the real thin part, so to totally eliminate potential cracking. What do the experts think?

I don't understand this part exactly. Removing material I don't think will help in this situation.....It looks to me like you don't have enough structure ("enough meat") there. The relatively sharp edge of the big spline also contributes to the stress riser.

I would look at jumping up a "size". If you can find a shop that specializes in driveshafts (even if its for truck shafts) they might be able to help at least supply the blank for it.

 

[OccupantRJ]

Braze a piece of keystock on each side of the week area, or use nickel welding rod to build it up.

 

[Barrymaxx]

Can you go up a size on the yoke then press a conversion U-joint in? That way you can start with a meatier yoke and maybe keep your driveshaft the same

1310 to 1350 for example... they make many sizes and combination.
https://www.dennysdriveshaft.com/p4..._combination_u_joint...neapco_greaseable.html

 

[2oolhound]

It's been a while since I worked with drive shafts. I'm surprised there are only 6 splines on these yokes. There used to be 3 times that many teeth. None the less it's the casting that is too thin. All to reduce production costs and raise stock holder's dividends.

I'm not sure where you'd machine this to improve strength. The stress risers appear to be coming from the valley of the splines and the crack moves from these valleys to the flange. Drilling a hole at the base of the flange into the spline valley may contain the crack to the spline valley but the flange is just too thin to begin with so I like the suggestions of building up the area with weld to add strength over all. If there was a bigger radius on the spline valleys it would help prevent cracking but it's still too thin. It's like Hardy Spicer tried to save money by machining out some yokes from a lighter assembly for a different vehicle instead of casting a heavier yoke. I'd complain to them and/or look some more for something beefier.

 

[MattT]

Looks like it might be a tractor yoke.

https://www.paulbparts.com/product-...s/tractor-yokes/?filter_spline-count=6-spline

Or failing that you might find something more suitable to modify here.

https://neapcocomponents.com/images/catalogs/2017_driveline_catalog_9901153.pdf

It's like Hardy Spicer tried to save money by machining out some yokes from a lighter assembly for a different vehicle instead of casting a heavier yoke. I'd complain to them and/or look some more for something beefier.

The OP machined it so I don't think complaining will help

 

[Hawke]

Many thanks for all the suggestions. While I can certainly go up a size, it would require changing out all the drive shafts, and adding some weight. Increasing rotational mass on a race car is never an advantage.

I may just beef up the thin part with some nickel weld rod, as I have a bunch of it in the shop. The frame is nickel bronze welded, as is much of the suspension.

Its all part of the joy of racing 45 year old cars, that were only intended to be driven for a season or so.

 

[beater74]

You aren't gonna win any races with broke ****.

 

[jayoldschool]

I'd send a PM to nastyzen and see what he says...