Adjusting for dead straight running - no RR

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.
Post Reply
PhantomVirus
Pine Head
Pine Head
Posts: 76
Joined: Wed Sep 29, 2010 9:58 pm
Location: Clinton, NJ

Adjusting for dead straight running - no RR

Post by PhantomVirus »

So most of my problem this year is that I started WAY too early and have the opportunity to tweak and 'adjust' the heck out of the car with weeks to still go before race day :wall: :wall:

If anyone remembers my saga last year - we (I) dropped the finished car off the kitchen table 2 days before the race and Cubbie & I had to scramble (on 2 school nights) to get a new one built....which swept pack & Districts.

So this year we built 2 cars (a snake and a broadhead arrow design) and we are 'testing them out' to see which he likes better. We have not done any axle prep or wheel prep but merely inserted the tires/axles into the block to test roll the cars. We did not drill the axle slots as we are required to use the slots and the last time I drilled them I came to realize that my drillpress is less than square. I am using the same Pro Axle Guide for insertion / gapping tool that I used last year to put the axles into the block.....http://www.maximum-velocity.com/pro-axleguide.htm" target="_blank

When I roll the car on my test board (we need all 4 wheels on the floor and no perceived camber) the cars roll 4-6 inches to the RIGHT across 4 feet. In comparison, last years winner moves less than 1/4 in across the same distance....that car rolls straight as you can point.

Our track is a 40' aluminum one and staying true / not on the rail did well for us last year - several other rail riders failed miserably - so I would like to true these cars up to run pretty close to straight.

Recommendations on alignment that I should look to do to get them to run true? The axles and wheels look like they are inserted properly, the weights are centered on the cars and the COMs are near 5/8th inch forward from the rear axle slots.

(Sorry for the spelling errors - typing on an iPAD is not my best work)

Thx
R
Last edited by PhantomVirus on Fri Jan 06, 2012 10:01 am, edited 1 time in total.
User avatar
pwrd by tungsten
Master Pine Head
Master Pine Head
Posts: 723
Joined: Wed May 24, 2006 1:51 am
Location: Seattle, WA

Re: Adjusting for dead straight running - no RR

Post by pwrd by tungsten »

Well,

I would narrow the front end on both sides. I would also roll them forward and backwards (once with wheels against body and once with wheels against axle heads. Then report back here what you observe with regards to wheels shifting to the axle heads/body.
W Racing!!!!
PhantomVirus
Pine Head
Pine Head
Posts: 76
Joined: Wed Sep 29, 2010 9:58 pm
Location: Clinton, NJ

Re: Adjusting for dead straight running - no RR

Post by PhantomVirus »

you mean physically cut the front end in front of the axles? tapering it?
now that I think of it last year's car was pointy and this year's are broad and flat.......

or do you mean sanding the width of the car down over the front axles?

thx
User avatar
Stan Pope
Pine Head Legend
Pine Head Legend
Posts: 6856
Joined: Sat Jul 05, 2003 7:01 pm
Location: Morton, Illinois
Contact:

Re: Adjusting for dead straight running - no RR

Post by Stan Pope »

Re the "no perceived camber" rule ... How is this inspected?

If I could slide a piece of common copier paper under one side of the wheel more than 3/4 of the way across, would this be considered "perceived camber?" If so, then the rule is pretty tight, and you probably better use the rear wheel alignment ideas described in http://www.stanpope.net/lbw4c.htm#e, at least for sensing rear wheel alignment. That process greatly reduces alignment drag. (Rear axle alignment drag is the likely cause of problems experienced by RR's last year.) You might try twisting nearly straight axles instead of shimming (just because it is a lot easier), but it is likely that alignment will not converge with that method, since twisting an axle exchanges between toe and camber, whereas shimming attacks toe and camber separately, allowing each to be optimized.

Once the 4 wheels are aligned for dead-on straight alignment, tweak the most dominant front wheel with enough toe-in to keep it on the rail. Because of your 'no camber rule", you probably need to use only a small amount of bend in that axle. Then verify that the rear wheels stay away from the rail.

On the other hand, if the test for "perceived camber" is less sensitive, then you can undertake a more RR approach, but focus very carefully on getting the rears working together (avoiding alignment drag). Even very slightly cambered rear wheels improve run times if their alignment is right. Forward/reverse roll test, looking for the wheel to migrate out should be accurate if only small amounts or rear camber are used. (For this test, the car should run is a straight line forward and backward.)

You could avoid all this alignment pain IF
1. you can drill/pilot true axle holes/paths, and
2. you know what to target for those true hole/paths, and
3. you can make your axles straight enough so that their deviation from straightness doesn't foul your alignment, and
4. you can recognize, when complete, that your results are as good as they can be.
I can't do that without a track to test on AND months of development time to hone the techniques.
Stan
"If it's not for the boys, it's for the birds!"
User avatar
whodathunkit
Pine Head Legend
Pine Head Legend
Posts: 2476
Joined: Sat Apr 25, 2009 5:56 pm
Location: Forgan, OK

Re: Adjusting for dead straight running - no RR

Post by whodathunkit »

PhantomVirus wrote:So most of my problem this year is that I started WAY too early and have the opportunity to tweak and 'adjust' the heck out of the car

So this year we built 2 cars (a snake and a broadhead arrow design) and we are 'testing them out' to see which he likes better. We have not done any axle prep or wheel prep but merely inserted the tires/axles into the block to test roll the cars. We did not drill the axle slots as we are required to use
:thinking: Stan, what effect would the unpreped axle play?
when the axel or nail is made it is nothing more the wire that is heated.
It is when the tooling pinches and grabs the wire..
that a head is hamered forming the head of the nail..
next it is cut forming the point.

So i guess what I'm asking is about is the egg shapeing that happend
when the heated nail/axel was made and the burrs or crimp marks were
formed. What effect could the egg shapeing play?

Thanks for the tips Stan.
Last edited by whodathunkit on Fri Jan 06, 2012 11:46 am, edited 1 time in total.
What type of automobile can be spelled the same forwards & backwards?
PhantomVirus
Pine Head
Pine Head
Posts: 76
Joined: Wed Sep 29, 2010 9:58 pm
Location: Clinton, NJ

Re: Adjusting for dead straight running - no RR

Post by PhantomVirus »

Thanks - you continue to amaze me Stan - I wish I knew what you forgot.......

The camber thing is more eyeballing the wheels on a rolling board (as we test to make sure we have 4 on the floor).

RR concerns me as it seems like the friction on the inside front wheel would slow the car down in the flat...i know I am missing something but the entire RR concept seems counterintuitive. I am going to re-read the RR threads an try to understand....and yes I am another 'visual' learner.

We shall see how this goes ;-)
User avatar
sporty
Pine Head Legend
Pine Head Legend
Posts: 3344
Joined: Sun Feb 13, 2005 1:00 am
Location: rockfalls, Illinois

Re: Adjusting for dead straight running - no RR

Post by sporty »

Making a strait runner.

What you should think about doing. Is getting a 4 inch wide, semi smooth board or ect. 4 foot long.

Take the front wheels off, if the bottom of the car is not been sanding or distorted. meaning still flat.

Take a piece of clear tape and put under the nose of the car, makes it smoother for this testing.


Raise the board up 4 to 6 inches, where the car will roll all the way down the board, not to fast, but enough to finish the 4 foot lenght.

Adjust the rear wheels, until the car stays on the board all the way down.

then add a wheel in the front and run the car down again, adjust the front wheel, until the car goes strait down the board.

If you are required to have 4 wheels touching, repeat the process with the 4th wheel on the front.


You also want to, narrow the front end of the car about 1/8th of a inch on each side, meaning the wood. You will want to do this before tuning the car.


Other mentions:


Canting is better and provides less contact with the surface of the track. and also helps with the wheels staying out towards the axle head of the car. (no rubbing on the body)

If your rules allow it and you are not to far into the car build already.

There our various articles on here on how to cant.

If you are deciding to give it a go. I would likely suggest a mild cant for a strait running car. in the front and perhaps a little more in the rear.

example

1 degree in the front

2 degrees in the rear.

Now I seen, you are concerned with RR, you are worried about it causing more friction. If you were to due a RR car.

Simply put, a non RR car, often hits several times during the race on the track guide rail. slowing you down and causing loss of speed, especially if this happens at various points of the track.

A RR car, simply controls the amount of touching the car does to the track guide. and provides you with more consistent track times.

While a strait runner can go faster, when done perfect. More often than not. very few people are able to achieve this. And always unless you have a track or time to run on the actual track before the race (track the race is held on).

So those variables are harder to come buy for a strait runner.

So many of us, run RR now, and initial learning can be a bit hard, but no harder than learning how to do a strait runner.

I have been doing RR for 3 years now and it has given us a mroe stable and consistent car and faster than our old strait runner days.

Because even I had trouble making a perfect strait runner. I migth see one super fast run out of 5 to 6 runs. Where the RR would give me fast runs almost every run.

There is a different tuning process to RR and that can be tricky to a new comer and without a test track. but can be done with a tuning board or tuning set up and soem average drift (safe numbers) to use.

Sporty
User avatar
FatSebastian
Pine Head Legend
Pine Head Legend
Posts: 2803
Joined: Wed Jun 17, 2009 2:49 pm
Location: Boogerton, PA

Re: Adjusting for dead straight running - no RR

Post by FatSebastian »

PhantomVirus wrote:I am missing something but the entire RR concept seems counterintuitive. I am going to re-read the RR threads an try to understand....and yes I am another 'visual' learner.
PhantomVirus, we have no personal experience with four on the floor rules, but Sporty has lots. I was going to suggest that you contact Sporty who generously shares some of his "four on the floor" tricks historically by PM, but it seems that you already requested and received this benefit last year! I don't know if Sporty's post just now covers the material he also shares via PM.
User avatar
Stan Pope
Pine Head Legend
Pine Head Legend
Posts: 6856
Joined: Sat Jul 05, 2003 7:01 pm
Location: Morton, Illinois
Contact:

Re: Adjusting for dead straight running - no RR

Post by Stan Pope »

whodathunkit wrote: ...
So i guess what I'm asking is about is the egg shapeing that happend
when the heated nail/axel was made and the burrs or crimp marks were
formed. What effect could the egg shapeing play?
Well, if the axle were spinning, then the egg shape would do nasty things to your car's performance. But, since it isn't spinning, the slight egg shape should cause the axle to be able to nestle better into the bore ... if that is the side of the axle that ends up lowest! If the major axis of the axle cross section is vertical (egg standing on end), then it is not as good, tho still okay.

Bottom line, the axle doesn't have to be exactly round to function well. But it better be smooth. :)
Stan
"If it's not for the boys, it's for the birds!"
User avatar
Stan Pope
Pine Head Legend
Pine Head Legend
Posts: 6856
Joined: Sat Jul 05, 2003 7:01 pm
Location: Morton, Illinois
Contact:

Re: Adjusting for dead straight running - no RR

Post by Stan Pope »

PhantomVirus wrote:I wish I knew what you forgot
Me, too! :)
PhantomVirus wrote:The camber thing is more eyeballing the wheels on a rolling board (as we test to make sure we have 4 on the floor).
...
Well, if you are involved with inspection, add a step using a 1X3" strip of paper. When the car rolls to a stop, try to slide the end of the paper under the wheels from the outside, then the inside. Keep track of how many wheels you test and how many wheels would fail if that test were applied for real. Then decide what to recommend to the rule makers.

When/if the end fo the strip becomes crumpled, turn it around and use the other end. Should start with a dozen or so slips of paper, depending on how many cars you inspect.
Stan
"If it's not for the boys, it's for the birds!"
User avatar
pwrd by tungsten
Master Pine Head
Master Pine Head
Posts: 723
Joined: Wed May 24, 2006 1:51 am
Location: Seattle, WA

Re: Adjusting for dead straight running - no RR

Post by pwrd by tungsten »

PhantomVirus wrote:you mean physically cut the front end in front of the axles? tapering it?
now that I think of it last year's car was pointy and this year's are broad and flat.......

or do you mean sanding the width of the car down over the front axles?

thx
Less wood between the front axles. Front wheels close together keeps rears off rail.
W Racing!!!!
Post Reply