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Tosion Bar suspension
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enjenjo
Rookie


Joined: 23 Jun 2021
Posts: 49
Location: swanton ohio

Posted: Mon Jul 12, 2020 8:43 am    Post subject:

You could use Sprint car torsion bars, they are splined on each end for adjustment. They are about 30" long, and available in many rates. I have used them to make anti roll bars, and they work great for that too. Midget bars are a bit shorter. they should be fairly easy to get in OZ, I know they race sprint cars down under.
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GBS
Just Idling



Joined: 18 May 2021
Posts: 161
Location: Central Coast NSW

Posted: Mon Jul 12, 2020 10:49 pm    Post subject:

Peter

I have been looking closely at the rear end photo again and even with a magnifying glass the drive shaft looks very close to the torsion bar but if your drawing shows the shaft going between the top and bottom arms then that must be right.

One thing I canít see though is any bar connecting the top arms. The top arms are shown with a cap bolted over the ends which I would assume is covering the lock nut. No matter how hard I look though, I can not see any shaft or bar connecting the two. There is just open space between them with a lot of what looks like flexible brake hoses running to the twin piston Dunlop calipers.

Unfortunately we canít run down the street and have a look at one. Chassis number XKD 510 was for sale on the cover of Unique Cars magazine about five years ago for about $950,000! I think it is now back in England and was probably the last one in the country.

I did find one in a Parramatta Road used car yard in about 1963. It had ex Jack Davey and 2,400 pounds written on the windscreen. That car is also back in England today. That was about the closest I ever came to owning one but unfortunately 2,400 was double the price of a new Holden at the time and a little too much for a second year apprentice.

Brian
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jeffallen
Guest





Posted: Tue Jul 13, 2020 12:35 am    Post subject: Torsion bars.

A very simple torsion bar rear suspension would be (each side): a torsion bar fixed at the forward end (well, adjustable as normal), going rearwards: a bush/pivot at the beginning of the rear wheel arch, then the wide end of an "A" arm fixed to the torsion bar, then another bush/pivot fixed to the chassis towards the rear of the wheel opening. The "A" arm being the lower arm of a twin wishbone independent system. You could then use (say) late model Commodore diff and axles. The only bug could be the amount of lateral movement of each hub with suspension travel. That is determined by the length of the "A" arms. To get enough length, you'd need to mount the torsion bar inside the chassis. The length of the "A" arm will also determine the spring rate of the torsion bar, so it would be a compromise.
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Mr34
Just Idling



Joined: 11 Jun 2021
Posts: 105
Location: QLD

Posted: Sun Jul 18, 2020 7:44 pm    Post subject:

I think i have figured out a way to set it up, so that it works. It is like the method written about by jeffallen, but with just a lever at the rear connecting to the diff, not an A-arm.
The length of the lever will dictate the spring rate which has been mentioned here, so i think if the lever is as long as the A-arm of the car that it came off, then it will be the same as the donor car.

Beign that the Donor car would probably be a light truck - Ford courier/ Hilux etc, a 4 cyl, it should be able to carry the load of the rear end of a car, being that there is no engine back there.

I will draw it up see if it looks ok.....
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PeterR
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Posted: Sat Jul 31, 2020 12:20 pm    Post subject: PIC FOR GBS

PeterR wrote:
In response to GBS

The only picture I have of the D is a phantom line drawing viewed from the rear.

The top pair of arms are joined at the front by a transverse bar that appears to be about 20mm dia and I assume works in conjunction with the arms as an anti roll bar. The bar has a thread on each end with nylock style nut to hold the whole assembly together.

The bottom pair run rearwards from a transverse tube about 75mm diameter housing the torsion bar. There is a single torsion bar, anchored in the middle of the tube. The bar has a thread and nut on each end similar to the top.

The apex of the A arm is pivoted under the pumpkin of the diff assy. The feet of the A pivot at the bulkhead. The horizontal plane of the A arm appears to be about one third of the distance up from the lower arms.

The drive shaft passes about mid height between the two transverse bars.

If the photo you have is taken on an oblique angle the leg of the A arm could easily be mistaken for the torsion bar giving the appearance you describe.


The pic below is the D type rear I attempted to describe earlier with the text above.

GBS, you should sprint to the local newsagent, the June copy of Motor Sport has a cover article on 50 years since the D type.


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GBS
Just Idling



Joined: 18 May 2021
Posts: 161
Location: Central Coast NSW

Posted: Tue Aug 03, 2020 10:30 pm    Post subject:

Thanks Peter. I have had another close look at the photo I have and there is definately no bar connecting the top trailing arms. Maybe not all of them used sway bars. Who knows, there is usually a lot of experimenting going on with racing cars so anything is possible.

Do you know what those bulky things are that go in from each wheel and drop down in front of the axle housings? There are also not shown in the photo.

Brian
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Posted: Tue Aug 03, 2020 11:56 pm    Post subject:

GBS wrote:

Do you know what those bulky things are that go in from each wheel and drop down in front of the axle housings? There are also not shown in the photo.
Brian


Had me guessing for a while, but I believe they are sheet metal ducts to run cool air out to the rear disks. They appear to have a rectangular cross section about the same size as the diameter of the axle tubes. The square piece that hangs down just outboard of the diff centre is the forward facing air inlet, the duct then sweeps up, curves through 90 degrees and runs out in front of the axle tube to the discharge over the disk which is hidden in the left wheel but visible inside the right wheel.
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PeterR
Guest





Posted: Tue Aug 03, 2020 11:57 pm    Post subject:

GBS wrote:

Do you know what those bulky things are that go in from each wheel and drop down in front of the axle housings? There are also not shown in the photo.
Brian


Had me guessing for a while, but I believe they are sheet metal ducts to run cool air out to the rear disks. They appear to have a rectangular cross section about the same size as the diameter of the axle tubes. The square piece that hangs down just outboard of the diff centre is the forward facing air inlet, the duct then sweeps up, curves through 90 degrees and runs out in front of the axle tube to the discharge over the disk which is hidden in the left wheel but visible inside the right wheel.
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GBS
Just Idling



Joined: 18 May 2021
Posts: 161
Location: Central Coast NSW

Posted: Sat Aug 07, 2020 11:05 pm    Post subject:

Peter

I suppose brake ducts are about all those things could be but what a weird way to design them. I would have thought a better way would have been to run a large diameter flexible hose from the disc forward to a small oval shaped scoop protruding below rear edge of the belly pan. Those sections hanging below the axle housings look like they would cause some drag which would not worry a road car but could easily be a problem at Le Mans considering these things were touching 180 mph down the straight.

Brian
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PeterR
Guest





Posted: Sun Aug 08, 2020 1:35 am    Post subject:

High-speed drag might not be such an issue. There could be a reason for mounting the ducts on the axle.

Remember, this is a four bar rear so does not produce any rear-end anti-lift under braking. I am guessing that the bottom edge of the scoop is level with the belly pan when the vehicle is at static ride height. Under power or coast conditions the scoop will be above the draft and consequently not contribute to drag. However when the brakes are applied, the rear of the body (including the belly pan) lifts, and this would expose the duct openings to full under-car draft.

If my guess is correct then the amount of air discharged over the brakes will be modulated by the amount of braking and is another example of Jaguar cleverness, ---but then my guess might be completely off the mark and the layout is just another bit of Jaguar weirdness.
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GBS
Just Idling



Joined: 18 May 2021
Posts: 161
Location: Central Coast NSW

Posted: Sun Aug 08, 2020 7:30 pm    Post subject:

Peter
It is also possible Jaguar did not design them. These cars were bought by racing teams all over the world and who knows how many alterations were made. Jaguar did lengthened the nose on their works cars, made changes to the windscreen design and altered the shape of the tailfin just to name a few changes. If they did design them, they may not have been fitted to all Ds.

One point to consider is the fact that the D was built for Le Mans only. It was very successful there but was not particularly outstanding anywhere else. Le Mans is a long circuit and while speeds are high in places, I am not sure if it is noted as being hard on brakes. Brake cooling ducts may not have been considered necessary.

When you look at these ducts I can't help thinking they look like an afterthought. They could have been added by someone in an attempt to make the car more competitive on a tighter circuit.

On another subject: I have never ceased to be amazed at the performance Jaguar got from that little twin cam, hemi headed, 3.4 litre inline six. A production D covered the quarter mile in about 14.5 seconds and had a top speed of 165 mph. The works cars were a second faster an could almost reach 180. Both versions could be driven easily in city traffic. Thats not bad for the early to mid 1950s.

If only Chrysler had turned to Jaguar instead of Peugeot for the technology to build their hemi heads. A quad cam hemi would go quite nicely in my roadster.

Brian
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