Axle height

[Guest]

So I've read all the threads regarding axle height and I'm still unclear. 1/8" high for canted rears from the bottom up. Is that from the bottom of the car to the bottom of the hole or bottom of the car to the center of the hole? Not really sure what heights to start with- would 1/8" rears and 3/16" DFW be a good starting point?

 

[pony express]

I think that drilling the holes that deep lowers the center of gravity too much. At one time I did not think that was possible, but I tried drilling some cars at 8/32 (the center of the bit is at 8/32) and they were slow. I tried 6/32 and they were a little faster, but still not up to speed with the other guys. I did some research and it has to do with the roll couple and the center of gravity. The magic number is like 5 Kids and others have said in the past: about 5/32. I have not tried 4/32. There's probably a best depth, but I'm not sure what it is. Stay around 5/32. The center of the bit/axle should be about 5/32 from the bottom of the block.

 

[Guest]

Thank you so much for clarifying. I just double checked and it looks like I'm set up at 4.5/32"- close enough for horseshoes and hand grenades! If my understanding is correct this will slightly lower the nose lessening the effects of rear wheels being toed out which may or not be a good thing regarding stability.

 

[Guest]

What's a good height for the DFW to start out with?

 

[5KidsRacing]

The last couple years I have drilled everything .125" up from the bottom to the center of the hole.... I never found that drilling the DFW different than the rears gave me any speed.

 

[Guest]

Sweet!

 

[GravityX]

+1 on what 5Kids said, the last car I built I drilled all the axle holes the same height. By coincidence or not, it has been one of my fastest cars to date.

 

[Falcon777]

If all the holes then are drilled at .125 or 5/32, at what height do you drill the NDFW? Thanks!

 

[GravityX]

If all the holes then are drilled at .125 or 5/32, at what height do you drill the NDFW? Thanks!

I usually drill at the same height because the bend in the axle at the DFW will raise the front of the car. That should be enough to raise the NDFW to clear the track.

 

[5KidsRacing]

I drill mine the same height too... I just cut all of the weight off of the OD and width of the lifted wheel. If you use an old style BSA wheel you can get your lifted wheel to about 1" in diameter which gives it a small profile.

 

[DEW36]

I drill mine the same height too... I just cut all of the weight off of the OD and width of the lifted wheel. If you use an old style BSA wheel you can get your lifted wheel to about 1" in diameter which gives it a small profile.

That's very creative!!!

 

[pony express]

I have tradionally drilled the DFW 1/32 lower than the rears. When I mean lower I mean that the hole will be closer to the bottom of the block. I guess i've been doing it so long I can't remember where it came from. I'm now try to determine if that's the right height. The hole drilled lower raises the front end slightly. I'm hoping it creates a slight caster angle, that is if you believe you can get caster out of these cars. It would take a whole lot of testing to get the comparison results. It's too late in the season to experiment now. Stick with what you have confidence in. Confidence leads to careful observation.

 

[Minions Racing]

Here's another tool I'm working on to help visualize the relationship between axle hole heights and caster angle. You can manipulate the height of the axle hole and the camber of front and back axles.

http://jsfiddle.net/minionsracing/zCn7S/embedded/result/

I haven't tested it as much as my other one. I eventually want to add a view from the front and view from the back. Another adjustment on there is the wheel offset, which I call the distance between the center of the axle hole where it intersects the plane of the side of the car body and the center of the axle where it intersects the plane of the inner rim of the tire. So basically the gap plus the any part of the hub that sticks out past inside of the wheel. I tried to give reasonable default values?

Again, no promises that it actually is correct. But I thought it related to this discussion.

 

[pony express]

I like it. That is cool.

 

[Papa V Racing]

Minions Racing - Awesome work in progress you have....

Papa V

 

[rkirkwo1]

Minions Racing, Pure awesomeness!!!

I can now trash the spreadsheet I started for the same thing!

 

[Obsessedderbydad]

Question... If you have the DFW lower than the rears, wouldn't this give you less potential energy since the majority of the weight is more forward now because of the DFW being lowered? Or am I thinking about this backwards?

 

[GravityX]

In my experience, raising or lowering the car does not shift the weight on the wheels. For the most part the weight remains unchanged for the degree or so of elevation change you'll see in the car. I've taken my cars and raised the DFW scale up 1/4" higher than the other scales and the weight was still reported as the same. I don't know at what point you would start to see a change, but you wouldn't be racing a car at this point, it would be a ramp, in my opinion.

 

[Obsessedderbydad]

Then why do top fuel dragsters have a higher rear wheel?

I was just wondering because of the Potential Energy formula. The higher the weight the more PE, whats = speed.

 

[GravityX]

Then why do top fuel dragsters have a higher rear wheel?

I was just wondering because of the Potential Energy formula. The higher the weight the more PE, whats = speed.

Why does a farm tractor have a higher rear wheel?