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Old 09-09-2013, 06:52 PM   #91 (permalink)
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owly -- It's novel to see people advocating for rear-steer, so I have some questions, if you don't mind.
  • Do you have a cite-able reference one could point to in discussions of the subject?
  • What was the top speed of the truck/loader?

Quote:
I've been a Buckminster Fuller admirer since the 60's........ so I'm biased toward the Dymaxion. I only wish there was some info about his rear steering geometry available on the web.... Thus far I've had no luck. The downfall of the Dymaxion I believe was the weight distribution.
Me too. Except I think the downfall was aerodynamic lift on the lee side of the nose in crosswinds.

It seems testable with a recumbent tricycle. If the rear wheel rotated fore-and-aft on a pin at the top of the fork; and there existed two plates, one on the frame and one on the fork, that had 10 holes in an arc on one plate and 9 holes on the other—then the inclination could be adjusted to 1/10th the hole spacing. For test purposes.

If rear steer were applied to this vehicle, the result would be 3-wheel steering.

I haven't checked back through the thread but I believe I suggested turning the top torsion bar into anti-roll, that would shift the spring/roll ratio considerably.

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Old 09-09-2013, 09:24 PM   #92 (permalink)
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Quote:
Originally Posted by freebeard View Post
owly -- It's novel to see people advocating for rear-steer, so I have some questions, if you don't mind.
  • Do you have a cite-able reference one could point to in discussions of the subject?
  • What was the top speed of the truck/loader?



Me too. Except I think the downfall was aerodynamic lift on the lee side of the nose in crosswinds.

It seems testable with a recumbent tricycle. If the rear wheel rotated fore-and-aft on a pin at the top of the fork; and there existed two plates, one on the frame and one on the fork, that had 10 holes in an arc on one plate and 9 holes on the other—then the inclination could be adjusted to 1/10th the hole spacing. For test purposes.

If rear steer were applied to this vehicle, the result would be 3-wheel steering.

I haven't checked back through the thread but I believe I suggested turning the top torsion bar into anti-roll, that would shift the spring/roll ratio considerably.
Interesting idea on using the top torsion bar as an anti-roll bar. I know the suspension is not compressing to any significant degree with the stock torsion bar setup. I assume you are talking about disabling-removing the center anchor for the torsion bar itself?

Thanks to everyone else for suggestions-support!

regards
Mech
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Old 09-10-2013, 12:11 AM   #93 (permalink)
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Best of luck O.M.! Almost a twin of that 2 seat (side by side) Eco Commuter a few years back. It was to be a 750 CC with power windows, air conditioning, etc. It did have an excellent cloaking device - vanished and is still invisible!
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Old 09-10-2013, 03:04 AM   #94 (permalink)
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Outstanding O.M....absolutely outstanding Sir! I am headed to the Portland Oregon this Friday after work as the Elio Motors team will be stopping there on their national tour. They will be there this Th/Fr/Sa/Su there showing off their Tadpole three-wheeled cars and I am excited to see one of them! I am Sub'd and anxiously watching your build. Keep up the great work! :{)

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Old 09-10-2013, 04:41 AM   #95 (permalink)
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Quote:
Originally Posted by freebeard at #54
Since the stock torsion bars are about 200% of your requirement, just remove the upper grub screw at the center of the torsion bar and it will float freely and act as a stiff ant-roll bar...I think. And if you want to throw money at weight problems, the steel front torsion beam is available in aluminum (for offroad use in Calif.) as a sand buggy part.

I haven't done it myself, but it's easy enough to try it and then put the screw back if there are unintended consequences.

I think you did yourself a favor with the choice of a standard Beetle front axle. You can go wider, narrower, lighter or airbags; all with over-the-counter parts.

When I saw this, I thought of the question of skinning over that beautiful framework. This would be lighter. And you could make some panels perforated for air vents. Bead roll right over the perfs.
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Old 09-10-2013, 11:27 AM   #96 (permalink)
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An anti roll or sway bar must be free floating to work properly. It forces one side to do what the other side does, so that if the suspension on the right compresses, the suspension on the other must also compress, or twist the sway bar. I'm not at all sure how the top torsion bar on a VW front suspension would do this.......... You don't want to make the suspension more stiff, you just want to snub body roll.
The rabbit had a wonderfully simple rear suspension that was in itself a sway bar. an Ibeam spanned the width of the car, and was attached by two rubber bushings like spring bushings. The two trailing arms were fastened to the Ibeam and used shock struts. For one side to move independently of the other, the ibeam had to twist. A simple and elegant solution.

Howard

I haven't checked back through the thread but I believe I suggested turning the top torsion bar into anti-roll, that would shift the spring/roll ratio considerably.[/QUOTE]
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Old 09-10-2013, 01:03 PM   #97 (permalink)
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[QUOTE=freebeard;389621]owly -- It's novel to see people advocating for rear-steer, so I have some questions, if you don't mind.
  • Do you have a cite-able reference one could point to in discussions of the subject?
  • What was the top speed of the truck/loader?

I don't have any references.......... I built quite a few of the reverse truck loaders back in the 80's. At first they were a handful to drive....... worse if you didn't reverse the axle. Then I built one that was so wild you couldn't keep it on the road much over walking speed. That experience forced me to analyze what the problem was. As it turned out, when you turned right, the roll of the frame was actually causing the steering force to increase due to the angle of the drag link downward from the steering box to the axle. The solution was simple. I built an idler which was mounted low so that the drag link ran at a slight upward angle instead of a steep downward angle. After this, you could run at 50 mph with no problems. It was rock stable. Since that machine, ever one I built has had an idler except one that I put straight hydraulic steering on. The steering cylinder mount on that one is mounted just a bit low so it has the same effect....... as the body rolls it tends to steer very slightly back toward center.

The difference in stability on the wild one between before and after I put the idler on was stunning! It was every bit as stable as the truck I built it from at that point.

One very common system that has been used on many of these is a large idler under he frame, and the axle not reversed. It's terrible. Though the idler makes the drag link run more or less straight, the reverse caster makes them wild to control.

Note that the trucks originally have the steering box mounted very low, and quite close to the axle so the drag link is more or less straight. Reversing the vehicle makes this impossible obviously, but an idler in the same relative position would solve the problem.

The one where I originally solved the problem was built in 1981, and is still being used on a regular basis....... it was pretty high class. Had a full reversed cab, heater, windshield wipers, radio, the works, and used the original N series truck nose, with a truck cab backed up to it.

Howard
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Old 09-10-2013, 01:58 PM   #98 (permalink)
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Old 09-10-2013, 02:19 PM   #99 (permalink)
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Some more pictures. The front suspension is barely compressed as it is, so it will be very stiff. I think the way to make the upper torsion bar (actually a group of flat bars clamped together) function as an anti sway bar would be to release the center support and let the bar free float between the trailing arms. That may actually work out to be ideal but right now the ground clearance is 7 inches and I don't want it much lower than that. Probably leave it alone for now and see how it rides, then try it with the upper torsion bar center clamp released. That might make it ride better without compromising handling, but as long as it is reversible then it is easy to try it both ways. Even with 450 additional pounds of weight the front suspension compresses maybe 1 more inch.

Aerohead, the dimensions I gave you were off some.
Height 50 inches
Width 63 inches
Ground clearance 7 inches (included in height)
I did some rough claculations.
63X18 inches rectangle to 25 inches off the ground as it sits with 7 inch ground clearance.
That's right around 8.013 square feet.
The top is (as you pointed out) not a perfect semicircle. It's 25 inches high (versus 31.5) so I calculated the area of a circle, then divided it by half (semicircle). The I guessed the difference in area at 90% versus a complete semicircle.
While not super precise (over 45 years since I took any relevant math) I calculated it at 9.741 feet, giving a total of 17.754 swaure feet not including the protruding part of the 3tires, which I am planning on putting flexible dams in front and possibly behind the front tires and a dam-skid plate in front of the rear tire.
As you stated before the CD sould be .15, hopefully lower and the frontal area at around 18.5 square feet total, top speed might actually be pushing 70 MPH. Eventually I will find out.

I'll post the pics next post, been timing out on longer posts.

regards
Mech

Last edited by user removed; 09-10-2013 at 02:27 PM..
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Old 09-10-2013, 02:23 PM   #100 (permalink)
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Pictures as promised.

regards
Mech

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