A hypothetical, theoretical discussion.

Ol'fogasaurus · Post by **Ol'fogasaurus** » Sun Mar 15, 2009 5:08 pm

Like I said, I was concentrating so hard on travel I completely missed your point on stored energy. It is a well taken point and I stand informed. I get a big “Duh” on that one!

I had a similar problem when I tried to keep the tires and the body separated on my buggy by using Gabriel air shocks (they were on the buggy when I got it). When I put in enough air to separate the two then the pogo effect you talked about was there (they do little if any dampening). I almost endowed the buggy in some whoops (a rhythm section) at the bottom of the main dune at Sand Lake. I went several body lengths on the front tires before it finally came down. As the bouncing was getting worse as I was going though the whoops, I was afraid to even touch the brakes as if I had hit them at the wrong time, it probably could have made the bouncing of the rear of the car so it could go the rest of the way over. It felt that close. I just let off on the gas and felt that at the time, that was the best I could do. I had the convertible top in the car at the time and I could only see sand though the windshield. I also had just seat belts and a show bar. Not safe! The air shocks came off as soon as I got home.

Got thinking, another part of the equation is wheel base. I have been told several times that the 80 inch wheel base (of a glass buggy) is too short to put a lot of travel in. Either or nine inches is probably max. I have been told this several times and it makes sense I guess. Opinions…?

I am also seeing several people build IRS on the front of buggies also.

A lot of good information coming out. Thanks guys.

Edited once to clarify.

ntsqd · Post by **ntsqd** » Tue Mar 17, 2009 8:03 am

I'm cutting up Skid's comments because it helps illustrate a couple points, not because I am picking on him.

Skidmark wrote:I really like the adjustability of the SAW center section on mine. I cranked it up a bit before the Anza Borrego run a few weeks ago. I ended up taking about half of the increase in preload out before the run (at the camp site). When you add preload, the ride gets harsher real fast, and the tendency to bounce increases.

Torsion bars have a very high rising rate percentage, much more that coil springs. Years ago I was talking to Mert Lawwill about his MTB rear suspension design and rising rate came up. He said then that he wanted to see about 7%-9% rising rate. I've no idea if this translates to vehicle suspensions, but lacking any other info I've used it as a ball park RoT.

I don't have easy access to nitrogen to add a little more pressure to the rezzy's to see if that would help.

The owner of the class 10 car that I chased taught me that T-bar suspensions want the reservoir plumbed to the extension end of the damper. He has been around off road VW based vehicles since knee high. By plumbing the res to the bottom of the damper you force the rebound displaced oil to go thru the damper piston.
Adding pressure increases the damper's "spring rate." They do have a spring rate, it is the area of the damper shaft times the charge pressure. So it's not much, but it does exist.
You make things slightly worse by increasing the charge pressure because you increase the damper's spring rate.

I would love to have wheel scales to see what is on each wheel, but don't have the coin for purely data collection equipment.

This is an easy one to make if welding is available. The only moderately difficult part is deciding to destroy a 1/2" drive socket for the project. I'd suggest buying a cheap one just for this.
It uses a beam style torque wrench as the "scale". Usually the horizontal tube is set to have a 10:1 ratio between the two ends when the length of the torque wrench is included.

In use the lip sticking up on the short end engages the wheel in question. You push down on the torque wrench handle until the tire comes off the ground. Slip a piece of paper under the tire. Then set the tire back down. While gently pulling on the paper slowly push down on the wrench handle and read the 'torque' number when the paper first slips out (a helper is a bonus!). Multiply that number by the ratio and you have a corner weight.

Ol'fogasaurus · Post by **Ol'fogasaurus** » Tue Mar 17, 2009 9:11 am

My, my, my, what we do come up with around here. I hope this string continues on. A lot of good is coming out of it.

Thank you for the great information ntsqd

Post by **david58** » Tue Mar 17, 2009 11:48 am

ntsqd wrote:This is an easy one to make if welding is available. The only moderately difficult part is deciding to destroy a 1/2" drive socket for the project. I'd suggest buying a cheap one just for this.
It uses a beam style torque wrench as the "scale". Usually the horizontal tube is set to have a 10:1 ratio between the two ends when the length of the torque wrench is included.

In use the lip sticking up on the short end engages the wheel in question. You push down on the torque wrench handle until the tire comes off the ground. Slip a piece of paper under the tire. Then set the tire back down. While gently pulling on the paper slowly push down on the wrench handle and read the 'torque' number when the paper first slips out (a helper is a bonus!). Multiply that number by the ratio and you have a corner weight.

Could you go into a little more detail on making these? Very interesting and affordable.

Skidmark · Post by **Skidmark** » Tue Mar 17, 2009 12:53 pm

Cool idea, but not sure where I would want to hook onto my aluminum BTR's anywhere... I don't want to leave marks.

Post by **david58** » Tue Mar 17, 2009 1:31 pm

Skidmark wrote:Cool idea, but not sure where I would want to hook onto my aluminum BTR's anywhere... I don't want to leave marks.

You could add a rubber pad to it.

ntsqd · Post by **ntsqd** » Tue Mar 17, 2009 1:34 pm

We used one, commercially made, to rough-in the set-up of the Vintage racers. To protect their really expensive wheels ($1000+ each in some cases) we put a piece of rubber fuel hose, slit length-wise, over the lifting lip.

The teal and blue parts telescope and the pin allows you to choose the hole that sets the height of the lever so that when the lifting tip is in contact with the rim, the lever is level. The lever pivots on the shown bolt. Not much more to it, but since I've got one and have used it my familiarity with it might be overlooking something.

fusername · Post by **fusername** » Tue Mar 17, 2009 1:49 pm

just a second idea, if you are worried about damaging your rim, maybe hooking a rope over it and using tire chains? or one of those webs used to hold tires on trailers, but under the tire instead of over. Beautifuly simple however, better than my idea.

4 bathroom scales off ebay
1 piece of plywood.

I think you can guess the rest.

TallKewl7 · Post by **TallKewl7** » Tue Mar 17, 2009 2:18 pm

fusername wrote:
4 bathroom scales off ebay
1 piece of plywood.

I think you can guess the rest.

4 bathroom scales that will weigh 300 lbs each. 4 x 300 = 1200. My car weighs 1800 lbs.......ummmmm, Houston we have a problem. However, there are setups that use bathroom scales to weigh cars, you just have to use some physics and leverage. I tried to find a photo that showed these in use, and couldn't. I have seen them in use. But it's basically using a lever and some math to figure out each corner weight.

Marshall

Ol'fogasaurus · Post by **Ol'fogasaurus** » Tue Mar 17, 2009 2:25 pm

With a little bit on ingenuity, that design could be converted to an off-road jack also.... HEDROCK!

Post by **david58** » Tue Mar 17, 2009 3:56 pm

Ol'fogasaurus wrote:With a little bit on ingenuity, that design could be converted to an off-road jack also.... HEDROCK!

Why is everybody pickin on Hedrock

Ol'fogasaurus · Post by **Ol'fogasaurus** » Tue Mar 17, 2009 4:23 pm

Not picking on him, just trying to get his attention.

We've been talkingon and off about jacks that's why. This could break down and store pretty flat by the use of pins plus be adjustable in height using pins also.

It is the locking it in the lift position that would need to be worked out. I am sure one of the guys here could figure out something based roughly on the design. Some pretty smart and ingenious people join us here. It is worth planting the idea anyway.

Post by **Hedrock** » Tue Mar 17, 2009 6:36 pm

Lee... I don't think that it would be real difficult to turn this into a jack. If I ever get my car done I think I'll give it a try

.

Post by **david58** » Tue Mar 17, 2009 6:41 pm

We will be waiting.

ntsqd · Post by **ntsqd** » Thu Mar 19, 2009 10:08 am

Easy to see, since I've done it, how this can lift a wheel. But how would it hold it while lifted?

I'm thinking to pursue my poor man's King Jack by trying to find a light weight trailer tongue jack that has enough travel.