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Author Topic: Lakester rear suspension  (Read 14575 times)
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oj
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« Reply #15 on: November 06, 2016, 04:24:26 PM »

Swing arm rear axles were one of the reasons the rear engine modified roadster disappeared from the scene for several years.

DW

thats sounds ominous, can you elaborate?
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RichFox
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« Reply #16 on: November 06, 2016, 04:30:05 PM »

When Al built the roadster that i have now, he went with the swing axle design that had been in Hop Up years ago. Still in there now. Al went with torsion bars. And I shortened them considerably to increase the rate. Al also incorporated pretty tight stops so that the tires couldn't tuck under a whole bunch. It seemed to have worked for him. At the speeds that I ran the car it was fine. I think it may be time for the car to find a new home. If someone bought it today they would likely change everything about the rear and frame entirely.
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oj
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« Reply #17 on: November 06, 2016, 04:59:53 PM »

When Al built the roadster that i have now, he went with the swing axle design that had been in Hop Up years ago. Still in there now. Al went with torsion bars. And I shortened them considerably to increase the rate. Al also incorporated pretty tight stops so that the tires couldn't tuck under a whole bunch. It seemed to have worked for him. At the speeds that I ran the car it was fine. I think it may be time for the car to find a new home. If someone bought it today they would likely change everything about the rear and frame entirely.

Thanks Rich.  I keep thinking about the one Marty Strode built, do you remember it?  T roadster, driver up front with blown flattie in the rear?  The engine, trans & rear were swing arm (I guess I'm using the right term) and he said he'd do it again, said it worked fine.
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SPARKY
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« Reply #18 on: November 06, 2016, 07:27:29 PM »

I suspect not all went to such lengths to limit travel and/or lift.
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« Reply #19 on: November 06, 2016, 10:22:09 PM »

Years ago I used to frequent Tom Beatty's shop off of Glenoaks Blvd, in Sun Valley. We would talk about all kinds of stuff but mostly Bonneville and El Mirage and his Belly Tank which had a swing axle, with only one universal on each side, just like a early VW Bug. 

He told me about the time he was invited to run his belly tank at a dirt track oval in the Los Angeles area. He said in qualifying he was going way too fast into the first turn and said to himself that he messed up, but had to turn the wheel, and to his amazement the car stuck and did not roll as he had anticipated. Ended up setting the fastest qualifying time. As I recall they did not let him race after the qualifying run as the car literally put grooves in the track from the tires. If you think about this scenario the tank body rolled to the right which dipped the right axle and lifted the left axle which made the wheels look like \  \  going around the turn, which would make them dig in, hence the grooves in the track.

He also told me about running at El Mirage, making a U turn after the run and passing the push  truck on the way to pick him up.

Nothing wrong with running a swing axle, what you have to look out for is the body you put over it. Some work better than others.

IMO early REMR suffered from short wheel base. 90 - 100 inch wheel base and driver in front. Driver had maybe 48 inches of hood to look down, and could not feel when the car was coming around, then when they realized what was going on it was too late, spin and possible crash.

Tom G.
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Jack Gifford
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« Reply #20 on: November 07, 2016, 12:21:19 AM »

The orginal topic here concerned a sprung rear subframe which holds the engine, trans, and a rigid rear axle. Looks like some posts now relate to swing-axle rear suspensions.
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oj
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« Reply #21 on: November 07, 2016, 08:37:45 AM »

The orginal topic here concerned a sprung rear subframe which holds the engine, trans, and a rigid rear axle. Looks like some posts now relate to swing-axle rear suspensions.

I am getting confused to the terminology.  Can you explain what a 'swing axle' is.  The term 'sprung rear subframe' is good for me and describes what I am considering to do, is there a different term for it?
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SPARKY
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« Reply #22 on: November 07, 2016, 09:28:45 AM »

PJ post # 14 describes a swing axle   a VW has a swing axel
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Miss LIBERTY,  changing TKI  to noise, dust and RUST!!!

The # 1 issue is: TO KEEP THE REPUBLIC      
   Center for Self Governance            tncsg.org     mrspowell.org

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller
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« Reply #23 on: November 07, 2016, 10:27:06 AM »

PJ post # 14 describes a swing axle   a VW has a swing axel

An OLD VW has a swing axle, and OLD Corvair has a swing axle. Bad idea.

Regards, Neil  Tucson, AZ
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Regards, Neil  Tucson, AZ
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« Reply #24 on: November 07, 2016, 10:29:18 AM »

Swing axle


* TheImpossibleTankpic10.jpg (204.35 KB, 649x685 - viewed 105 times.)
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4-barrel Mike
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« Reply #25 on: November 07, 2016, 10:59:46 AM »

Another.  Summers Brothers-built quickchange:



Mike
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Mike Kelly - PROUD owner of the V4F that powered the #1931 VGC to a 82.803 mph record in 2008!
oj
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« Reply #26 on: November 07, 2016, 11:00:45 AM »

Gotcha.  Bad juju that.
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Jack Gifford
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« Reply #27 on: February 01, 2017, 01:27:53 AM »

... a rear-engine modified roadster... which suspended just the rear of the drivetrain via hinged front engine mounts, I realize that's an option for me...
After more thought, I'm leaning toward this "suspended rear subframe" approach. The scheme that looks attractive to me would pivot the front/center of the subframe on a balljoint anchored to a chassis crossmember about 10" ahead of the flywheel The subframe itself would be an A-frame with the 'point' of the 'A' at the balljoint, and the legs of the 'A' rigidly attached the the rear axle housing about where the present radius arms mount (radius arms would go away but track bar would remain). Torque reaction of the axle housing would be via an aluminum bulkhead between the legs of the 'A' and bolted to the pinion flange. A bulkhead at the inline QC would also attach to those legs to react driveline torque to the subframe. A triangulated-beam structure would extend past the 'point' of the 'A' to provide front engine support (merely support, to avoid any torque stress on the engine block). I like the fact that the existing torsion bar independent suspension would still be functional at all four corners- although I would only provide for a couple of inches of rear wheel travel. Not ideal from an unsprung-weight standpoint, but it would at least provide somewhat of a rear suspension.
« Last Edit: February 01, 2017, 01:35:27 AM by Jack Gifford » Logged

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oj
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« Reply #28 on: February 01, 2017, 09:12:26 AM »

Something to consider:  if the 'pivot' point is below the rear axle then when the wheels are driving the car and the car is heavier than the rear subframe then the wheel will try to drive over the pivot point and effectively 'lift' them over the pivot.  If the pivot point is at the axle centerline then it'd be 'neutral'.  If the pivot point above axle centerline then the wheels would be driven into the ground.  In automotive parlance it is referred to as 'Squat' and 'AntiSquat'.
Mechanical ratios also come into play.
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Jack Gifford
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« Reply #29 on: February 02, 2017, 02:12:13 AM »

"Squat/anti-squat" are very important considerations for dragrace vehicles. But not terribly significant for my F-class lakester- geared for 200+ MPH (only one drive ratio during runs), with just 182 c.i. for power. Nevertheless, my initial profile-view sketch shows almost neutral "squat" characteristics.

The main drawbacks I see are 1) low sprung/unsprung weight ratio, and 2) increased vehicle weight (a liability for 1.0/1.5 mile LSR).
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