Landracing Forum
Tech Information => Steering - Suspension - Rear End => Topic started by: Ratliff on July 12, 2008, 04:20:08 PM
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Illustration from the book "Race Car Design" by Len Terry.
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Looks rather like a Honda S360/S600 IRS setup:
Motor Trend on the S600: "Mated to a four-speed manual tranny, power flows aft to a chassis-mounted differential connecting to two motorcycle-style chain-drive units that turn the rear wheels and function like trailing arms-truly a novel independent-rear-suspension design. And instead of sedan bodywork, Honda dressed this high-tech chassis as a sport roadster..."
The S360 was first (?) shown at the Tokyo Motor Show in 1961.
I had an S600 in '72-73.
Mike
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Although it never got off the drawing board, Terry came up with his design in 1962. Perhaps somewhere along the way, through Terry's later work with Indy and sports cars, there's a connection to the Honda design.
Although you'd end up with four chain drives, this drivetrain concept of Terry's when combined with his suspension concept would allow a rear engine independent suspension car with as much weight as possible on the rear wheels while still using a conventional transmission and rear end instead of a transaxle.
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Since the wheel path doesn't follow the axle center, what keeps the chain on the sprocket during suspension travel?
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woops
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Since the wheel path doesn't follow the axle center, what keeps the chain on the sprocket during suspension travel?
The same thing that keeps the chain on a motorcycle's sprockets, i.e. the chain and sprockets moving up and down in the same vertical plane.
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Although you'd end up with four chain drives, this drivetrain concept of Terry's when combined with his suspension concept would allow a rear engine independent suspension car with as much weight as possible on the rear wheels while still using a conventional transmission and rear end instead of a transaxle.
Which would also give you a lot less unsprung weight - an advantage in handling. But other than cost savings and the ability to use off-the-shelf components, do you see any advantage to such a powertrain arrangement other than traction in straight line performance? I'm thinking a transaxle would be more efficient, offer better packaging, and be less prone to failure than chains (or belts).
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One thing this system allows is that the engine/trans is mounted very low. The crankshaft centerline is below the rear axle center line by as much as you can get away with. Ever wonder why NT3 is so low? follow the drive someday
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"the chain and sprockets moving up and down in the same vertical plane"
No, the angle and track width change with suspension travel. Is there some "floater" device in the hub that allows the sprocket to self-align?
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Although you'd end up with four chain drives, this drivetrain concept of Terry's when combined with his suspension concept would allow a rear engine independent suspension car with as much weight as possible on the rear wheels while still using a conventional transmission and rear end instead of a transaxle.
Which would also give you a lot less unsprung weight - an advantage in handling. But other than cost savings and the ability to use off-the-shelf components, do you see any advantage to such a powertrain arrangement other than traction in straight line performance? I'm thinking a transaxle would be more efficient, offer better packaging, and be less prone to failure than chains (or belts).
Transaxles are usually the best solution, if you can get one with the appropriate gear ratios. However, Rich's comment about being able to lower the engine as much as possible was something I hadn't realized.
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The Honda chain-drive IRS:
(http://pagesperso-orange.fr/club.honda.snz.fr/Images/Chain%20Type.jpg)
Mike
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"Transaxles are usually the best solution, if you can get one with the appropriate gear ratios'
If you can find an old Weismann trans axle, Weismann will convert it so you can run just about any ratio you want. Or buy a new one at 25K. Al Teague ran he first Wesiamnn built trans axle serial number 001, that came out Jack Brabam's indy car in his stream liner.
If you haven't heard of Weismann, he designed the locker rear end and the Ford top loader transmission in the 60's and helped a small Ford built car (GT-40) to dominate European racing. http://www.weismann.net
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(http://purplesagetradingpost.com/sumner/bvillecar/frame-rear-23.jpg)
My solution, I hope,
Sum
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So Ratliff and Panic, let's see if I'm understanding the point of contention.
In the actual drawings we're looking over here, it appears that the swing axis of the A-arm is at ~20-25 degree angle to the drive wheel axis which is parallel at rest (or should be) to the power take-off axis of the differential. I think Panic's point, and correct me if I'm wrong, is that the chain drive would have to remain in a perpendicular plane to both the power differential output axis and the drive wheel axis, or else twisting of the chain (or belt) would occur causing binding or stretch over the arc of the suspension travel.
Mike's Honda drive takes that into consideration, because the drive sprockets and wheel sprockets are on the same vertical plane.
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Yah, the motion path for anything but parallel to the axle will sweep the sprockets outboard, and out of plane by the complement (?) of the swingarm pivot angle unless some mechanical fix is employed.
I can see some small float on the sprocket (splines like a half-shaft should work fine, but $$, weight, complexity), but not rotation - because that would require its own trailing arm to dictate the path.
Changing the pivot to parallel cures the whole thing, but the built-in camber pattern (which I assume was the a major purpose?) is gone.
For a really limited range of motion the chain might tolerate it, and if power/weight are low enough the usual #530 chain on #520 sprockets gives a bit of leeway.
A toothed (Gilmer) belt would tolerate rotation fairly well if long enough (longer than shown unless very narrow), but not lateral displacement. A V belt will do both, but not with much power.
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750 club racing is still alive and well in the U.K. and today, as in 62, the rules require front engine and conventional (non irs) rear axles in some classes. I would guess this was his attempt to legally circumvent the rear axle rule and gain the benefits of a irs. FWIW- a couple of pics of current 750 club tech. :
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750 club racing is still alive and well in the U.K. and today, as in 62, the rules require front engine and conventional (non irs) rear axles in some classes. I would guess this was his attempt to legally circumvent the rear axle rule and gain the benefits of a irs. FWIW- a couple of pics of current 750 club tech. :
That was precisely Terry's intention.