different wheel diameters on same car

[chromegsx]

thinking outside the box a little here and need some opinions...

Would you think there would be any theoretical advantage to having different diameter wheels on front and back...provided you maintain the proper ratio to make both size wheels make 1 revolution at the same time. I.e. .098 bore, to 1.190 dia gives 12.14286 distance ratio of dia:bore. So a .0985 bore dia would need a 1.196 OD to get the same distance covered. I would think this is definitely desired.

Or would there be some advantange to intentionally having the front wheel designed so that the axle was intentionally riding "down" or "up" the wheel bore so to speak?

Does that make any sense? I have no reason to believe this makes a difference, just a thought that occured while supervising my son as he questioned the fairness of using the best parts from 2 different kits purchased. So I was thinking if you are limited on the kit you've been given, You could work the diameters so the the bore/outside diameters would work together so that both wheel sizes make exactly one full turn together. So that thought led to... could you work the differences in wheel bore sizes to your advantage by making the outside diameter to a designed difference to force the axle to the front or back side of the bore?

 

[bracketracer]

Off the top of my head I'm going to say that the circumference of the wheel determines the distance covered per revolution, not the bore diameter? Maybe I missed something?

 

[chromegsx]

Yes not what I was asking. Not sure how to explain the chaos of my thoughts... hmmmm....

 

[IAE Racing]

I'm just going to point out something here as it relates to several things (rules)be discussed currently. Here is chromegsx thinking out side the box looking for an advantage to get his block of wood to the bottom faster. Duh, that's the point. Maybe we should make a rule against thinking. Heck they do it (don't think) in DC all the time.

 

[IAE Racing]

BTW Chrome, I get what your asking. I do weigh each wheel of all the kits separately then place according to that. IE. lightest on the scout car, heavier on the family car.

 

[Guest]

I'm just going to point out something here as it relates to several things (rules)be discussed currently. Here is chromegsx thinking out side the box looking for an advantage to get his block of wood to the bottom faster. Duh, that's the point. Maybe we should make a rule against thinking. Heck they do it (don't think) in DC all the time.

Hahahaha. Yes. "Thinking" should be discouraged at all times!

This is the earliest form of cheating.

I like this idea a lot. I'm not saying that I think it will add speed, but I like it non the less.

Perhaps though... I mean, perhaps the DFW wants a different amount of rotations to the rears due to slipping.

I bet the big dogs could answer that one.

 

[chromegsx]

Lol please don't go down the rules road with this. Was only pointing out the background of how I arrived at my conundrum.

Laserman seems to get what I'm after. It's actually a two part/context question. One as it relates to having a kit and doing the best with what you got and two taking it a step further as it relates to minimizing loss of speed on the flat by adjusting where the axle "wants" to ride in the bore.

My thoughts on the second part at this point is it might be a wash or a disadvantage as the rear axles would then want to ride differently as well as the front. And since there is more friction back there, you'd end up with a loss.

I'd attempt a test or ten if I had a clue and some consistent builds under my belt.

 

[Guest]

I'm sure the Big Dogs have played around with different bore to outer tread diameter ratio detail in greater detail than this puppy on the porch has ever dreamed of but I'll bark and paw in the dirt anyways/images/boards/smilies/smile.gif

I agree with Bracketracer that the outer diameter dictates total roll distance and is independent of bore size. As far as a reduced diameter front wheel being used to change where the axle sits in the bore, I would think any gains by reducing friction, if that's what actually happens would be offset by the rears being slightly towed in by the front now being lowered- that is if the rears are cambered. For straight rears it might be of benefit since rear toe wouldn't be affected. Having the smaller diameter wheel should reduce brake torque and start rolling with less effort but more lube and wear per run due to more revolutions. Then again the lower profile wheel should cut through the air faster. I think you came up with a great idea, I've been running scenarios in my head of what you proposed and I'm interested to see where it leads. Thanks for sharing and let us know the progress of this test and your boys bacon car.

 

[Guest]

Bracket definitely knows what he is talking about when it comes to wheels.

I was going to start down a hypothetical path but I made myself dizzy.

OK. I will start.... Who really cares if I don't even finish the thought, let alone come to any conclusions.

The car will only go as fast as the slowest wheel will allow it.

ahhhh. I can't do this. it is too late. The big dogs probably tested this stuff to death anyway.

It is a fun riddle though.

Maybe with the Dom a different size than the rears it will not "synch up" even though it is keeping up. Perhaps this is a good thing. Remember that bridge in San Fran that shook itself apart? Maybe there is a way of performing judo on the vibrations.

 

[chromegsx]

I'm sure the Big Dogs have played around with different bore to outer tread diameter ratio detail in greater detail than this puppy on the porch has ever dreamed of but I'll bark and paw in the dirt anyways/images/boards/smilies/smile.gif

Yes I've seen lots of text on bore/images/boards/smilies/redface.gifD ratios to the point of a whole car (all wheels being the same) car in general, but not independent. I've also seen lots on weights of wheels, but now wondering if there was any discussion on going lighter on the DFW vs. the rears since there is less weight on it. in effect moving that weight to the back of the car. bah... too much thinking with no way to test.

I agree with Bracketracer that the outer diameter dictates total roll distance and is independent of bore size. As far as a reduced diameter front wheel being used to change where the axle sits in the bore, I would think any gains by reducing friction, if that's what actually happens would be offset by the rears being slightly towed in by the front now being lowered- that is if the rears are cambered. For straight rears it might be of benefit since rear toe wouldn't be affected. Having the smaller diameter wheel should reduce brake torque and start rolling with less effort but more lube and wear per run due to more revolutions. Then again the lower profile wheel should cut through the air faster. I think you came up with a great idea, I've been running scenarios in my head of what you proposed and I'm interested to see where it leads. Thanks for sharing and let us know the progress of this test and your boys bacon car.

smaller bores mean less revolutions of the bore per the same OD of the wheel, therefore traveling axle on wheel travel distance is reduced... sort of like shortening your race compared to the same OD and larger bore. so they are not independent. As far as changing alignment I hadn't thought about that but I'm not talking something that's noticeable in OD sizes. I'm talking a thousandth or two or three maybe max. I didn't say smaller would be better, it could be larger, just depends on the bore size...I think it needs more explanation. I'll see if I can't come up with a picture or better words...with race time differences getting down to the ten thousandths I think it has merit worth exploring more, but I'm not involved in any racing like that.

Thanks for entertaining my thoughts, guess I'll have to keep thinking until the day comes I can test my own thoughts.

 

[5KidsRacing]

How do you adjust "where the axle rides in the bore"? Doesn't it always ride just forward of center? I mean if it rode just behind the center, the car would be going backwards.... right?

 

[chromegsx]

In my mind "you" are not "adjusting" it, friction is adjusting the wheelbase by way of the different bores & ODs and front/rear wheels turning at different rpms. but now that you mention it... and me saying it, it sounds like anything more than a few thousandths difference (clearance of axle to bore) will just work against you and create more friction and just points me back to the importance of keeping all wheels identical as the best course of action...assuming your kit doesn't vary more than can be corrected reasonably. i think I'm over-thinking it at this point. I like math so my wheels started spinning and may have gotten out of control. In my mind the wheelbase of the bore centers (not the axles) would be slight closer/farther (due to differences in diameters) forcing front axle to ride, slighty forward or backward of "normal" assuming "normal" meant all wheels had same bore and OD. In effect I was thinking you could get an oil lube under the axle sooner in the race for oil.

Some of this has got to sound /images/boards/smilies/crazy.gif. I think I see the asylum on caller ID.

 

[5KidsRacing]

Here is my take on axle/bore clearances and axle/wheel diameters.... and I know this is kinda off the subject chromegsx, but it has some common points....

Depending on how you prep your wheels and axles and how you use you oil and what spray you use and how much you apply, etc..., etc... you will have different sizes of everything that work for you. One guy might run great with large axles and tight bores while another may be exactly the opposite. How the oil/boundary layer lubricant (Jig) react in the wheel bore surely is affected by the clearance, but it probably is dependent on how much and what types is used.... So I think the key is for a guy to use a consistent prep method and to find the axle/wheel combination that works for that method, or you could do the opposite...

also, going off the subject again, I think that wheel OD/RPM has a lot to do with speed. I think your prep method likes a certain speed and performs best at that speed.... so with weight being equal some people will run better with larger OD wheels and others with smaller OD wheels. That being said, usually smaller OD wheels are better because the weight distribution in the wheel is more towards the bore... Do people run wheels that are different OD sizes on the front and the rears? yes... Is it faster? Probably for some, probably not for others, you just have to try it and see what works for you.

 

[Quicktimederby]

+1 I think you nailed it. Atleast from what i've tested.

Here is my take on axle/bore clearances and axle/wheel diameters.... and I know this is kinda off the subject chromegsx, but it has some common points....

Depending on how you prep your wheels and axles and how you use you oil and what spray you use and how much you apply, etc..., etc... you will have different sizes of everything that work for you. One guy might run great with large axles and tight bores while another may be exactly the opposite. How the oil/boundary layer lubricant (Jig) react in the wheel bore surely is affected by the clearance, but it probably is dependent on how much and what types I used.... So I think the key is for a guy to use a consistent prep method and to find the axle/wheel combination that works for that method, or you could do the opposite...

also, going off the subject again, I think that wheel OD/RPM has a lot to do with speed. I think your prep method likes a certain speed and performs best at that speed.... so with weight being equal some people will run better with larger OD wheels and others with smaller OD wheels. That being said, usually smaller OD wheels are better because the weight distribution in the wheel is more towards the bore... Do people run wheels that are different OD sizes on the front and the rears? yes... Is it faster? Probably for some, probably not for others, you just have to try it and see what works for you.

 

[chromegsx]

[video]http://youtu.be/QSHaERIvFNE?t=16s[/video]

Thanks 5kids

 

[Guest]

Ok. I keep thinking about this wheel question.

The way I see it each part of the car has particular needs.

Such as:

The front of the car should be light, and the rear wants to be dense.

The rear wheels riding on the inside edge of the tread while never touching the rail is a heckuva lot different than the DFW rolling on the outside of the tread/ inside edge on the guide rail, while steering into rail.

It seems to me that the DFW would want for something slightly different than a "normal" rear wheel.

What the DFW wants would probably take a Wheel Whisperer though.

Luckily there are a few on this forum so input from them is appreciated.

 

[Guest]

Perhaps it just "wants" to keep up with the rears since it is doing so much more work.

After all, the positive cant (body rub/ "climbing" the axle and oscillating back down with rail contact), plus sliding while spinning, AND being the third leg of the tripod (which is cantilevered out far out in front of the other two legs).

 

[Guest]

The special needs of each of the 3 wheels presents an unprecedented situation for this decade of builders. I feel that each individual wheel needs tending to, studying the behavior and nature when small tweeks are made. The front wheel may carry the lighter load but it is also on the front line and fights the battle alone! The floater just sits there rather than offering to share the burden of carrying the weight like the rears do. Having a larger DFW diameter may boost the "confidence" of the wheel but it may be "false confidence". A smaller diameter may get in there faster by keeping the brake torque closer to the center of the wheel. In my opinion wheel equality is overrated and needs to be studied with a fine tooth comb, their actions on the track are sending us communications, it's up to us to decipher what's being "said".

 

[Guest]

Well said Eccentric.

However it is not only OD/ ID combinations but also the bevel of the contact points and many other factors, as you know.

We must listen to all the needs of the cutting edge of the plow.

The rears seem more like the straight forward bull dozers doing their "natural" thing.

 

[Guest]

Great analogy Laserman!
I agree 100%- The traits of that DFW better be up to snuff when it runs that 42' gauntlet.
I view the DFW as a leader of the pack and the rears as followers. A true leader has qualities and traits that are worth being followed. I'm gonna chew on this awhile and see if anything "clicks" in my brain.