+- Austinsevenfriends (https://www.austinsevenfriends.co.uk/forum)
+-- Forum: Austin Seven Friends Forum (https://www.austinsevenfriends.co.uk/forum/forumdisplay.php?fid=1)
+--- Forum: Forum chat... (https://www.austinsevenfriends.co.uk/forum/forumdisplay.php?fid=14)
+--- Thread: Rear hub and halfshaft problems (/showthread.php?tid=4627)
Pages:
1
2
Rear hub and halfshaft problems - Denis Sweeney - 04-07-2020
I know the topic of rear hubs on A7’s has been aired on numerous occasions on this forum but in my short time on here I have not seen any mention of a couple of problems I have recently encountered.
The rear axle on my Ruby was originally rebuilt in 1988 complete with new half shafts purchased from A7 Services, Kirby Wiske, but maintaining the original hubs. The car was never completed at that time and never ran on the road with this set up, and was only ever driven in and out of the garage and up and down the drive.
In 2017 the rear hubs were stripped down again and checked. The hubs were not tight and there had been movement as witnessed by the markings on the taper and woodruff key. New outer hubs were purchased along with new keys, bearings, brakes, springs etc. The hubs were lapped onto the shafts and all made good.
Refer Pic 1 attached
However, the location of the split pin hole on the half shaft was located too far towards the end of the threaded portion to engage with any of the slots on the castellated nut.
Refer Pic 2 attached
After a period of time and miles I checked the tightness of the nuts and found the offside was still tight and ok whilst the nearside came away without any need for a hub removal tool at all. Needless to say the hub taper had suffered showing signs of chattering and the key was pretty distressed. I have carried out dye penetrant testing of the hubs and shafts and all sound.
However, examining the hub I note that on the inside of the new outer hub, there is scoring around the hub which I believe indicates that the outer hub, when fully tightened onto the bearing, is actually making contact with the end of the fixed axle. So I have dug out the old hubs and find that both the old outer hubs are badly scored on the inside too, which to me indicates the hubs, old and new were and are coming into contact with the end of the thread which the large nut goes on to lock the inner hub and bearing in place see below, old and new:
Refer pics 3 & 4
So before I do anything else can anyone please offer any words of wisdom and comfort on the following:
Is it considered acceptable to add a washer behind the castellated nut on the half shaft end so as to move the nut to a position where the split pins can lock the nut?
If not any other suggestions......?
And
If the outer portion of the hub is in contact with the fixed axle shaft can the end of the fixed axle be fettled down the minimum required to clear the hub?
FYI, I have checked the depths of the original and new hubs and they are within a few thou of each other.
The length of thread on the half shafts including the runoff is 0.8”
The distance from the end of the taper to the split pin hole is 0.685”
The runoff between the taper and start of the thread is 0.112”
Thanks for taking the time to read this and any comments welcomed.
Best Regards
Denis S
RE: Rear hub and halfshaft problems - Bruce Nicholls - 04-07-2020
No keys or split pins in my half shafts. The nuts never stop in the right place for the split pin holes. I do them up with a wheel with no centre on the hub to hold the hub still, using a socket with a long bar through the centre. Nothing has ever come loose.
RE: Rear hub and halfshaft problems - Colin Wilks - 04-07-2020
Well it's all gone quiet out there, so I shall pitch in, although I should say I have not yet had occasion to work on my rear hubs.
The taper on the shaft appears to me to have been lapped more than once in its lifetime and so the hub now is too near the centre line of the car.
The hub may be riding up on the woodruff key before it seats itself fully on the taper, which would explain it coming loose.
I don't know whether anyone has done either of these successfully, but two solutions come to mind (apart from shelling out for new half shafts), firstly to spray weld the tapers and turn new ones. Secondly, a bodge could be to cut a trapezoid shape from shim stock and sit this around the taper, bracketing the woodruff key.
If you are determined to stop the nuts rotating in their present position, there is just enough meat in the castellated bits to drill a chord to miss the threads and then wire them on through the split pin hole, à la military land rovers. If you're going to put a washer under the nut it would need to be hardened.
Good luck!
RE: Rear hub and halfshaft problems - Howard Wright - 04-07-2020
Hi Denis
It could be that the outer hub is riding on the key. If you fettle the key you should be able to pull the hub on the taper. The half shaft should have a bit of room at the pinion end. Try fitting the outer hub without the inner hub and check that it doesn’t bind with the axle end. If not then I think it is a new half shaft.
I have stopped lapping tapers and use a Loctite taperlock instead. After 80 odd years tapers are bound to be well worn! (Bitter experience of lapping a flywheel too much
.)Also remember that the outer hub nut needs tightening very hard. I use a 30” breaker bar and all my meagre weight behind it.
I think a hardened washer behind the nut is OK if you are worried about the split pin.
Cheers
Howard
RE: Rear hub and halfshaft problems - bob46320 - 04-07-2020
Colin, I have used a trapezoid shim as you wrote, squiggled together with "Liquid Metal" - works OK for a few thousand miles, but gave up in the end. I then a "re-metaled" the haft shaft where I had made up the taper with mild steel weld, filled the woodruff key (as a crack had started at that point) and re-machined a new one on the other side. That seems to be going much better and have not had to re-tighten the hub nut since. Plus 1 for some sort of Locktite product on the taper, make sure you have a good hub puller and good thread on the hub first !!
As for split pins, you could use a much smaller split pin if only half a hole is visible, its the taper that transmits the power, not the nut, not the split pin, not the woodruff key. The woodruff key is only there to stop the shaft rotating on the hub whilst you tighten the nut.
RE: Rear hub and halfshaft problems - Denis Sweeney - 04-07-2020
Thanks for the comments guys much appreciated, a couple of thoughts of my own.
My interpretation of the set up is that the hub has a fixed position and this is set solely by the fact that it is pressed hard against the rear half of the hub and bearing which itself has a fixed position and it is the half shaft that floats to suit, please correct me if that is wrong.
I understand and agree that the hub could be riding on the key and that would be a problem which I had thought of and will check, but it would also be a problem if the outer hub is actually contacting the fixed axle tube that the rear half of the hub and bearing are mounted upon which is what I believe is marking the outer hub.
Not sure how often you can lap a taper but the half shaft has only been lapped twice in its life and the taper does not pull through the hub ....as yet!
Not sure if this helps or hinders
Regards
Denis S
RE: Rear hub and halfshaft problems - Bob Culver - 04-07-2020
I dont really understand. The position of the hub relative to the fixed axle tube is determined only by the wheel bearing. I suppose it is possible the axle tubes have been machined back, maybe to prevent the axle binding in the diff housing, the usual outcome of enthusiastic lapping. But any rubbing would surely have been evident with the car jacked. The axle casing need not protrude far beyond the bearing retaining nut. i dont suppose there is some thin bearing which has been fitted, allowingthe hub to move in?
If a key has been so loose as to be hammered it is unusual for the axle not to be cracked, altho do not necessarily progress. The axle was/ is almost certainly so distorted as to require a lot of lapping to the detriment of the hub unless an old one used intitailly.
It is all very much more simple without a functional split pin.
It is important that the taper makes full and preferably exaggerated contact at the inner end so drive is transmitted before the key..
Other makes (Model A etc) get by with shims in the taper but do not have the very small area and high pressure of the Seven.
RE: Rear hub and halfshaft problems - Stuart Giles - 04-07-2020
halfshaft looks too short if the hub is contacting the axle casing. Being as the shafts came from Kirby Wiske, I wonder if they are from the same batch as the halfshaft featured in this earlier thread? the centre drilled end looks very similar to the one in your photos. https://www.austinsevenfriends.co.uk/forum/showthread.php?tid=3968&highlight=halfshaft
RE: Rear hub and halfshaft problems - Tony Press - 05-07-2020
As Bob said I don't understand the rubbing inside the hub - drawings show the hub is quite a distance from the axle tube.
As noted the distance between the axle tube and the hub is governed by the wheel bearing location on the axle tube and has nothing to do with the drive axle.
Has the bearing seating on the axle tube has been machined back ? If so the bearing retaining nut thread could extend past the nut as suggested.
The axle nut could be fitted with a washer but I would check all details before proceeding further- the drive axles appear suspect as well as the bearing seating on the axle tube.
RE: Rear hub and halfshaft problems - squeak - 05-07-2020
I have often added a varying thickness washer behind the axle nut to align the split pin, can also help to keep the grease and oil from escaping if you are using the small nut.
I have never had the outer hub contact the threaded casing BUT I have had the spur gear jam it's inner face against the diff carrier. This because of a worn taper. The solution at the time was to put the casing into the lath and remove a whisker (technical term) off the bearing land.
This sort of bodge could result in moving the outer hub closer to the casing thread. A shim/washer behind the inner bearing race (noting the radius) may work, or simpler if you can just file off a few threads.