Landracing Forum

Tech Information => Steering - Suspension - Rear End => Topic started by: Jonny Hotnuts on October 04, 2007, 12:25:18 PM

Title: how wide should the wheels be?
Post by: Jonny Hotnuts on October 04, 2007, 12:25:18 PM
Lets say someone wanted to run aluminum spinners (como el liners de Jack Costella proque 12" y no 8") that were 12" in dia but available in any width. I can see if they were too thin they would dig like ice skates on sand and if they were too wide they might "skip" and not be effective in turning.

So is there any rule of thumb reguarding the frontal contact patch size?
And are there any other concerns when using solid wheels like these?
Title: Re: how wide should the wheels be?
Post by: tortoise on October 04, 2007, 01:37:33 PM
And are there any other concerns when using solid wheels like these?
Mainly, they are able to generate very little steering force. You'd want a car that aerodynamically really likes to go straight, and the longest possible wheelbase. Muy despacio steering, too.

As to width, a good guess would be to have a contact patch to weight on the wheel ratio about the same as you-know-who.
Title: Re: how wide should the wheels be?
Post by: JackD on October 04, 2007, 01:39:05 PM
A zero contact patch will produce zero ability to transfer energy.
Something has to be deformed as the round part tries to grip the flat part .
Fail that, or leave a mark in the salt due to the design and you will bring down a lot of heat.  
Title: Re: how wide should the wheels be?
Post by: tortoise on October 04, 2007, 02:20:00 PM
. . . leave a mark in the salt due to the design and you will bring down a lot of heat.
An excessive mark, you must mean. Surely all vehicles leave some mark. Somewhere along the line, some official decided Costella's machines weren't a threat to the salt. Do you think that was a bad call?
Title: Re: how wide should the wheels be?
Post by: JackD on October 04, 2007, 07:23:40 PM
The design and it's effect on the condition of the surface dictates that call. :wink:
Title: Re: how wide should the wheels be?
Post by: Jonny Hotnuts on October 04, 2007, 08:34:38 PM
(http://www.fiatforum.com/gallery/data/500/small_copy.jpg?8455)
http://www.fiatforum.com/gallery/data/500/small_copy.jpg?8455

Jack, here is what I am thinking of.

I was considering using a series of rounded edge groves on a relatively wide surface area. The grooves should provide a lower slip coefficient (and hopefully better steering) while the overall width should prevent digging and possibly damage to the salt. If the aluminum wheels are the same width as my current tires (providing the weight is the same) and the edges are sufficiently rounded is there still a risk of salt damage?
Title: Re: how wide should the wheels be?
Post by: Unkl Ian on October 04, 2007, 08:39:12 PM
So what is the advantage of these solid wheels ?



And what is the price tag ?



My guess is they will be heavier than the typical pneumatic tires.
Title: Re: how wide should the wheels be?
Post by: Peter Jack on October 04, 2007, 08:44:38 PM
Jonny:

I don't know how much caster you'll be running but with any amount you'll be up on the single edge of each wheel rather quickly when you make a turn. I'd think you'd be better off with a single more rounded profile with a series of circumferential grooves.

Pete
Title: Re: how wide should the wheels be?
Post by: Jonny Hotnuts on October 04, 2007, 09:02:11 PM
Peter:

I was going to use a minimal amount of caster for this reason....maybe 5 degrees. I am going to have dampers and have the ratio really high so I was thinking I could get away with 0-5 degrees.


Quote
So what is the advantage of these solid wheels ?
And what is the price tag ?
My guess is they will be heavier than the typical pneumatic tires.


1. Good to any speed (not really a big deal with my car) but you can not find a speed rated wheel suitable for LSR under 22". These will be 12 and should never wear out or blow, but the 12" size is why I am opting for them.
2. I have a place that I can get 12" round 6061 T6 at any thickness......for instance on wheel 4"X12"
is around 150$ I will have the machine work done and will cost in the 50-100 range.
3. I need more forward weight, but at 12" I dont think it will be excessive.
Title: Re: how wide should the wheels be?
Post by: Unkl Ian on October 04, 2007, 11:39:50 PM
Airplane tires ?
Title: Re: how wide should the wheels be?
Post by: JackD on October 05, 2007, 01:18:16 AM
Airplane tires sound like an attractive alternative but don't be fooled by the speed or weight rating.
They are designed for a substantial impact on landing and very little duration at what is the rated speed.
They are designed heavy to absorb that kind of load and with the distance you expect to go they will build enough heat to destroy themselves.
The smaller diameter of the wheel and partial contact machined into the surface will further deform the salt as the area goes down.
While you are not transmitting forward motion through them the directional load is what is to be also considered.
Take a metal model of the wheel you propose and run it around a  table.
Now take just a wide rubber band or a series of narrow ones and put them on the wheel and try it again.
Title: Re: how wide should the wheels be?
Post by: Dean Los Angeles on October 05, 2007, 01:20:14 AM
Quote
2.F Tires
The use of . . . any non-pneumatic wheel/tire combination (no rubber) must be submitted for approval to the contest board in writing 45 days prior to an event.

The design you are showing is going to plow furrows down the salt. I think that might be a problem. Rubber allows for some compliance with the surface that aluminum doesn't.

In between a pneumatic tire and an aluminum one is an aluminum wheel with neoprene bonded to it. Something around Shore A 60 durometer (about tire tread hardness.)

Yeah, of course, while I'm typing, Jack beats me to the punch.

Title: Re: how wide should the wheels be?
Post by: Jonny Hotnuts on October 05, 2007, 12:26:52 PM
I don’t want to seem like I am being argumentative about this as I am only trying to sort it all out.

Dean:
You have a point about the furrows, but the 3d rendering is not to scale (and I may have exaggerated the grooves for the example). The factors to the furrows will be the weight of the car, width of the wheel, depth of the grooves and number of them. I intend to have the “wetted” surface in contact with the salt the same as my current tires patch width. The grooves would only be ¼ to 3/8s deep (not much different from my current tires tread).
I would love to know more about the neoprene ala “grumpy old men” but have no idea where to even start to look for info about doing this.


Jack:
Just curious, if I were to do the same test in sand as supposed to a hard table would my results be different with the rubber bands?

My real question is why the aluminum wheels work for the guys running them in the streamliner classes. Forget the grooves for this question it is just a matter of the wheels serving the purpose of steering on salt and decreased friction.
My car is in the process of being stretched to a 130” wheel base so why is there a huge difference between my car and something like the NT2 when it comes to front wheels?
Title: Re: how wide should the wheels be?
Post by: John Burk on October 05, 2007, 02:01:09 PM
"why is there a huge difference between my car and something like the NT2 when it comes to front wheels?"

NT2's front wheels carry maybe 30% of 1500 lbs (450) . Your front wheels carry 50% of 2600 lbs? plus the down force from your nose (2000?) .
Title: Re: how wide should the wheels be?
Post by: JackD on October 05, 2007, 02:53:18 PM
Sand, like the dirt at Blackrock is quite soft.
In the case of the thrust driven vehicle in the dirt, the groves that resulted from them running were a major contributor to the ability to direct the vehicle when underway.
A wheel driven vehicle is slowed so much by plowing a furrow at race speeds , it is not a suitable surface.
Sand is the same thing only different, and mud has the worst features of both.
Deform the surface to the point that others can't follow and you will be sat down on the salt.
When that is argued out to it's logical conclusion we can discuss relative safety.
A well known and very fast biker could be heard screaming over the sound of his ride when caught in a tire groove of a top of the line, wandering roadster,  " Gee I really hope he gets it straightened out soon.":wink:
Title: Re: how wide should the wheels be?
Post by: Jonny Hotnuts on October 05, 2007, 05:25:32 PM
I agree that my car weighs more than the NT2 (a good deal less than 2600) but how does the salt know the different between two tires of the same size made of different materials providing the weight is the same.
Would the car somehow have more of a tendency to sink and create impressions (ruts) just because you used a harder material? I can see how an aluminum wheel may not seer as well as a rubber but I dont understand how, providing the edge has a decent profile it would cause more damage than a standard tire.


Title: Re: how wide should the wheels be?
Post by: Unkl Ian on October 05, 2007, 05:58:08 PM
A pneumatic tire deflects under load,increasing the size of the contact patch.

A solid wheel won't.

--------

You'll also find that larger diameter tires give a larger contact patch,
compared to a smaller diameter tire of the same width.
Title: Re: how wide should the wheels be?
Post by: Dean Los Angeles on October 05, 2007, 06:01:00 PM
Wearing tennis shoes? Stand up. Pivot on the shoe. Not a lot, just enough to move it a tiny bit. Notice the squirm underneath as the rubber hangs on. Aluminum has zero compliance. If you look at a loaded, accelerating, turning tire you will see side wall distortion and tread distortion. That's the advantage. Aluminum doesn't do any of that, and when the salt is perfect you still have a marginal grip.

(http://www.nhra.com/2007/gallery/psm/Matt_Guidera.jpg)

I saw Andrés Segovia perform in 1984. 90 something and still spectacular.
Title: Re: how wide should the wheels be?
Post by: JackD on October 05, 2007, 06:08:39 PM
One or the other must yield to have a usable contact patch.
One design will leave smaller yield mark than the other and restore it's shape within it's design capabilities.
The other will cause the racing surface to yield if it is to have any contact patch and the mark will remain.
Steering Geometry does not have to tip the wheel in a turn as has been demonstrated with a of a lot of east of New York Drag Bikes and at least 1 Bonneville entry.  :wink:
Title: Re: how wide should the wheels be?
Post by: John Burk on October 05, 2007, 06:16:36 PM
It takes very little deflection to reduce the unit pressure . If a 24" tire only compresses .010" the contact patch is 1" long .
Title: Re: how wide should the wheels be?
Post by: JackD on October 05, 2007, 06:59:40 PM
How many remember the first time the Chet Herbert liner tried to run with solid aluminum wheels ?
When Vesco let the clutch out on the 4 motors, the wheels turned but it failed to proceed.
When it did finally move it only went a short ways before he turned out because the vibration back from the salt was so bad he couldn't see.
Title: Re: how wide should the wheels be?
Post by: Harold Bettes on October 06, 2007, 12:34:22 AM
Howdy All, :-D
 
Thanks to folks for the reports from the salt. Without them this place would be like the dark side of the moon.  :|

Relative to the "tire patch" issue: It is very easy to find out what you are dealing with by using something so simple as some paper and some carbon paper. 1) Jack up the vehicle and place plain white paper down on the floor under the tire. 2) Place carbon paper on top of the paper (carbon-ink side down). 3) Place another plain piece of white paper on top of the carbon paper sandwich. 4) Lower the vehicle on top of the carbon paper sandwich. 5) After imprinting the lower paper, again raise the vehicle and you can remove the carbon paper sandwich. The shadow of the carbon imprint is the tire patch. Although it is static and not dynamic, one can repeat the test with various conditions of inflation pressure and static weight and make an assessment of what the tire is doing by looking at the "tire patch".

This simple method is also very effective for checking conditions of "scrub" as well.

And next time we'll discuss cutting out paper dolls and sharing with others! LOL

Regards to All,
HB2
Title: Re: how wide should the wheels be?
Post by: JackD on October 06, 2007, 12:53:48 AM
In the absence of carbon paper that may be hard to find, you can wet roll it now before the water is all gone also.  :wink:
Title: Re: how wide should the wheels be?
Post by: Jonny Hotnuts on October 08, 2007, 10:46:44 PM
I hated doing it but I have decided to take everyone’s advice and not use the aluminum spinners this year. Originally I did not want to have to compromise on the frontal design by having a 22+” tire at 130” (22" is almost the height of the bottom of the windshield). After some discussion (with our technical advisor ;) )on the wheels I have opted for and acquired the LSR proven 14” front tires made by Goodyear. This will let me build the front and still be able to swap to the spinners when the time is right, and have a backup if there is any heat from tech.