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Re: TUBULAR FRONT AXLE

Hi Frank,What was Charles Leith reason for moving track rod to the front.

Location: Tinopai NZ

Re: TUBULAR FRONT AXLE

If you move the track rod to the front you can use a straight bar rather than the Austin one which is bent to fit under the chassis. The reason is the Austin bar bends under the cornering forces and doesn't do wonders for toe stiffness.
I've never really had an understeer problem with my Austin, either. Except on the hairpin at Curborough where you have to really nail it coming out to bring the back end round.
However there are those that do. It's often due to too stiff a front end - lots of specials have shortened or spaced radius arms like we've been discussing, even with standard axles. also you need to consider the effect of springs - often the balance is not right front to rear. It's almost impossible to give an answer without seeing the car in question, but what I'd recommend to anyone is ignore the Internet and get a book by Alan Staniforth. He really knew what he was on about and wrote it in a readable manner with a pleasant absence of difficult maths.

Re: TUBULAR FRONT AXLE

Alan
If you move the track rod to the front you can use a straight bar rather than the Austin one which is bent to fit under the chassis. The reason is the Austin bar bends under the cornering forces and doesn't do wonders for toe stiffness.
I've never really had an understeer problem with my Austin, either. Except on the hairpin at Curborough where you have to really nail it coming out to bring the back end round.
However there are those that do. It's often due to too stiff a front end - lots of specials have shortened or spaced radius arms like we've been discussing, even with standard axles. also you need to consider the effect of springs - often the balance is not right front to rear. It's almost impossible to give an answer without seeing the car in question, but what I'd recommend to anyone is ignore the Internet and get a book by Alan Staniforth. He really knew what he was on about and wrote it in a readable manner with a pleasant absence of difficult maths.


Ah, the hairpin at Curborough, yes. But we only got it on entry for the first two practice runs during which the remains of the tyre softener applied over the winter was scrubbed off. After that everything was fine. Pardon at Prescott was always a bugger because you would sometimes get it there and sometimes not. You often see drivers apparently taking the corner too tightly and loosing grip on the inside, but what has really happened is that the predicted understeer just hasn't occurred.
By the way,we have two cars with short radius arms and one with the std setup which is why I found your reply so interesting and well put.

Re: TUBULAR FRONT AXLE

Depending how done a front track rod will likely change Ackerman, although at racing speeds a reduction would seem likely to reduce understeer. But if too unsuited the forced slip may decrease overall adhesion.

From experience and observation anything which increases instantaneous loads on tyres promotes loss of adhesion and hence if at the front understeer. Dirt track cars reduce s.a settings and fit soft torsion bars when the track is slippery. Some methods of locating the front axle ie locked shackle, short radius metal ended Panhard rod, esp if angled, seem likely to heighten instantaneous lateral loads as car traverses bumps.

Location: Auckland, NZ

Re: TUBULAR FRONT AXLE

I don't think Jamieson was a great chassis-man. Engines, and particularly superchargers, were his forte. Even though Lord Austin had his say-so, no serious road-racing car designer was building a new car with beam front axles by the mid-30s, Bugatti excepted and he had his own ideas.
The joint was first introduced (by Austin) on the Jamieson Sidevalve cars, not the Twin Cam. I suspect the reason is simple. A rigid tubular axle and radius arm assembly doesn't really allow roll at all. So one wheel cannot rise alone, and over the notoriously bumpy tracks of the thirties, particularly Brooklands, they must have been real handsful. Pat Driscall said the car was 15mph faster on Brooklands bankings after the modification.

Location: Richmond,Texas, USA

Re: TUBULAR FRONT AXLE

These pics are of the Duck/Sand racer at John Sutton's about 10 or more years ago and show the later fitted and probably Jamieson designed tubular front axle.
The design is different in detail and may pre-date the Side valve/Twin cam but appears to have a swivel joint on the near side.

The Ducks originally had a forged solid axle and split radius arms.
There is some flexibility in the forged axle but it will behave as an anti roll bar.

Note the damage to the crankcase, probably caused by the chassis twisting in use.





Re: TUBULAR FRONT AXLE

I recently had chance to examine an early model A based dirt track car. The rear axle had radius bars on each side, consisting of a light tubular open triangular frame, apex forward. The front comprised twin light tubular bars, one above the other, presumably only separated so castor could be adjusted. Both arrangements would have offered little twisting resistance. It was not clear if the adjustment threads at the front were locked or free to turn slightly, further reducing resistance.

Location: Auckland, NZ

Re: TUBULAR FRONT AXLE

On second thoughts, with Model A torque tube drive, the rear side mounted radius arms even more compromised than some Seven arrangemnts. But then the cars were not professional designs but amateur copy cat concoctions and only required to run for a few hours. The side sof the triangle section included bends possibly to allow stretch.

Location: Auckland, NZ