Hillman Imp Stub Axle Alternatives????

[scotts216]

I am in need of inforamtion on 20th century alternatives to the Hillman Imp stub axles as used on many vintage formula fords. The originals don't last, and I have been told that they are poorly designed and built. I know of one fellow in New Zealand who makes a new hub and re-splines it to match a re-cut splined axle. Anyone here in the states that has made/machined a replacement in good steel????? I thought that Wayne Mitchell had made a replacement, but I have not been able to find aby info to locate him?

I run predominantly right hand turns, and wear the LR side. They wear quite fast, and become so loose they become useless. I fixed one by brazing inside the hub, then filing out the grooves, then pressing in the hub - sort of an amateur broach.....Worked for one season.....

Anyone else have any similar problems?? Solutions?????? Thanks.........

[bob darcey]

Scott:

One alternative might be to convert the stub axles to the more common (vintage) design, where the flange and the axle are one-piece, and are constrained in the bearings by the half-shaft yoke with a large nut. The yoke is splined to the shaft, but the splines are humongous compared to the splines your car uses on the outer flange.

[Frank C]

Wayne Mitchell is at:
http://www.dogrings.com/

- Frank C

[Stu Pidd]

Check with the Ginetta crowd as they will have similar problems aqnd might have developed a cure.
I think the early Dulon FF's used a similar set up.

[Stu Pidd]

Wayne Mitchell
Unregistered User
(8/20/01 6:49 pm)
Hillman Imp stub axles
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I manufacture a redesigned stub axle with a one piece flange and shaft and a separate inboard yoke. It is used without any modification to the original cast upright unless the original FF manufacturer modified the Imp parts. Comes complete with bearings, new spacer, and drilled for whatever bolt pattern and bolt length you desire. Material is heat treated 4340. I will send a cross section of design to needy folks. We have about 4 sets running at present and about 6 sets in stock. Call for more details. 760-942-9170, Wayne Mitchell.
P.S. UPS me the uprights and we will install the new bits in your uprights for free. Just the cost of the update.

[Goldie]

Hi Scott:
I share your pain. Loads of old 1600s use the Imp stub axle and I believe the Mitchell fix was initially done for Wayne's Marches. The Imp axle is also used on the Lotus Europa and Dave Bean and JAE both are experts in that area. Either or both can supply a new axle but I don't know if it is an improved piece or not. Again each carry a very large tapered split lock washed that centers the hub and in theory should bite a bit and not loosen. I have purchased these and not used them yet but the idea looks good. Laying a pile of Loctite 638 or 609 retaining compound on the splines also helps. In the mean time, keep a 1.5" socket and torque wrench handy.
Dave

[scotts216]

Thanks for the replies all. More info and thoughts:

Other cars that I know of that use the Imp axle are Crossle, LeGrand, Elden, and Nike.

The fact that the left rear axle nut can come loose is not necessarily the main part of the problem. It is the cause of this problem that is the problem. As I was told by Brian Bradshaw of Imperwerks in New Zealand, the problem lies in the fact that the splines were not cut correctly in the first place, and also that the metal is not quite hard enough. When assembled, if there is looseness, then wear can occur from the splined shaft moving in the splined hub. More wear equals more wear, equals more wear, equals.....

As I am always trying to keep the costs of racing as low as possible, so I can continue to do it, I searched worldwide and found Impwerks who supplied me with 2 used ones. I figured this was the cheapest and best course of action. I changed both sides, and after several sessions, the whole thing was loose again...... The axle nut (LR only) is allowed to to move as the lock tab has some play, and the rotation under cornering load loosens the nut a bit. The key is that there is ANY movement allowed in the splines. The trick is to have NO movement in the splines, meaning a PRESS fit has to be made - Problem is, all that is left in the world is used shafts that have play in them......I was told by Peter at BAT, who raced "in the day" what they did back then, and he said that they just replaced the old ones every 2 races and put new ones in. By the way, the used shaft on the RR has never had this problem, but, as mentioned, we run tracks that are 70% RH turns...

I thought I had solved the problem, at the suggestion of a friend, by flowing brass (brazing rod) into the hub, then filing the hub splines back out with a square file (6 hrs worth--are we nuts???) I got it close, then pressed it together, peeling out the unnecessary brass - Worked for almost 2 seasons. Point is, I got rid of the movement. (I had one club member who told me how he would cut slivers off pop cans trying to stick them into the spaces in the splines....) After our season ending 1 1/2 hour enduro this past weekend, I found that the whole thing had loosened up and wallowed out the hub again......So, back to square one..... Obviously, that was a temporary fix......

By the way, if you mark the nut, you can see that the nut will not always move, and that the movement or loosness is because of the wear in the splines. I used lots of red loctite!!! to no real avail......

Additionally, the Imp axle ran a 31MM ID bearing next to the yoke, but this bearing, to my understanding is obsolete. It also had a raised race (about .200"). I ended up turning that bearing area down to 30MM, which is the same as the outer bearing area so as o be able to use a readily available bearing. Since using a normal bearing, I had to make a spacer that goes between the hub and the bearing race (.200" thick obviously.....)to take up the space left by not having the rasied or shouldered race on the original bearing.

I have found several people that have solutions, none of them cheap, but still looking. Wayne, I will give you a call to talk about yours.....
Can you turn around before Oct 1????

Thanks all for the help, and hope some of this is helpful to you other poor fellows with withering Imp shafts!!!!!!!

Regards, Scott

[Goldie]

Scott:
Send me your e-mail offline and I'll scan a lock washer for you to look at. It isn't easy to visualize. The taper centers the hub on the shaft and should reduce or eliminate the "working" between the two. The concept makes sense to me and also worth considering as a Europa owner put me on to them and that group consider them to be the fix.
Dave