Right/Left cube placement

Using JSFiddle and trying to get the proper weight on both sides. Scout build with 4.4 inch W/B. I have a Right DFW and it is telling me to keep the COM centered I need 70 gr on left and 51 on the right. that is 2/3rd of an ounce. I thought I read that only and additional 0.2 oz should go to the non-dominant side. Any help would be greatly appreciated. Thank you!!!

 

I’d worry more about the weight you have on your wheels rather than COM. Make sure your rears are close, but I’d suggest having the non dominant side rear anywhere between 0.1-0.2 oz heavier. Your also going to want your DFW to have somewhere between 0.4-.0.5 oz on it.

 

With that wheelbase I'd go .5-.6 on the dfw. That's pretty short.

 

Thank you both for your replies! Huge help!! Figured I'd include the wheelbase as it might be a factor.
Curious as to the physics why the more weight needed on the NDFW..assume it has to do with a keeping a more distributed load on 3 vs 4 wheels and the fact it is offset from center.

 

OK . My little ones and I just had our first test track day - wooden track nothing fancy, but in good shape and freshly waxed.
Here is our build...after realizing we needed WAY more steer than I anticipated, it started running pretty smoothly. The only thing is we kept getting a wobble or two on the straight of way but not like it was doing this for most of the run, so i think we are in good shape. Also the steer on this was like 10 inches(or maybe more?) over 4ft so not sure if I am doing something way wrong with the balancin or not. Any comments would be helpful.

Note this was neck-and-neck with with my "Open" car last year that won the District race with a 3.0697 (~12 fps on 36.83' Besttrack), so clocked fastest time between all district scouts and parents, etc.

Tweaks / suggestions welcome.

PS. I noted post paint and weighting my car length is 6.8 inches, how much does this hurt me in reality? My next build I won't be so careless.
Thanks!

 

Teo main things to look at when trying to run less steer is weight and gaps. If you keep wiggling on the track, move more weight to your DFW. And make sure your gaps aren’t too lose. If they are too lose or sloppy that will contribute to the wiggling, require more steer.

 

Thank you!! My theory is that last years car has a open hole in the nose in front of the axel, I think this helps with the aerodynamics, makes it more stable, but Ill adjust the weight and rerun.

 

B_Regal Racing posted this checklist years ago in response to a question about wiggles. I think it’s the most complete answer to your question that I’ve come across. I keep this list handy as I tune our scout cars.


Consider:

1) clean wheels of debris, graphite, and wax with mild abrasive pad/micromesh

2) check rear alignment

3) check steer; add more

4) rear wheel gaps too large; tighten gaps; check front as well

5) move weight forward (only adding a few grams to the FDW)

6) check rear wheels; hubs or edges deformed; replace

7) bore diameter not equal when measured at inside and outside hub; replace

8) repolish a new set of rear axles (diameter is too small)

9) repolish a new set of rear axles (rear axles slightly bent)


Could be any one or all of these things. 1 thru 5 are easy to do and usually can correct most problems.

 

This is super helpful and Ive been going through many of these in my head. Was very anal about the rear alignment, using Lboy methods. added lots of steer, so not those. maybe front wheel gap as was leaving a litle wide until nailed steer. Will think about the others. Thanks again!!

 

My fast Basx car placed 2nd at Nationals and took third at John's last race. It had a perfect drill and ran very well. After Nationals something happened and I'm not sure what, but it didn't run worth a crap for the next couple months. When I checked the drill, one of the rears was toed in quite a bit. My point being... sometimes things change.

My guess would be similar to T-bone.

Check all gaps

Move a bit more weight forward(4.4" wheelbase)

Check rear axles for slight bends


Ed's checklist is top notch and would be great to follow, these are just my gueses asto what it may be.

 

There was an incident where my 4 YO car catcher was daydreaming and my scouts car slammed into the ground causing a small chip to appear near the left axle, I promptly epoxyed and lightly clamped. I didn't recheck for alignment issues but this could be the culprit. I was still running fast but just not the same as before.
Question, if I am at 18.5 on the front DW... what do you suggest I start with as far as adding weight. 20 or 19.5?

 

If it was running decent, before the incident, I think you should check the alignment first and see if it's still good.

 

How big a chip is it? If it’s a crack or chip enough to see the actual axle hole, there is no regluing. That has happened to me 2 or 3 times were shipping has cracked the rear axle brace on a car and I didn’t realize. Tuning them is not possible because the alightment changes every time. So if that’s the case then I’d build a new one and glue 1/64 inch plywood to either side of the brace for your next build.

if it’s a chip that isn’t deep or anything then you can re glue it, just as long as no glue comes within the axle hole.

 

Thankfully it did not appear to breach the axle hole and i avoided using any thin superglue as i didn't want it running in to the wheel...yes i have made that mistake before...so once i check the alignment i should know. Would love to pick up an original SB if anyone has one laying around to perform the LB aligment test as true as it is supposed to be. I put some set screws ala scott acton in there to help with alignment so maybe i can adjust those. Thanks TBone!!

 

Are you running scout axles or ss? All scout axles are bent to some degree and if installed in the rear, it could cause you tons of frustration. That is why it is never recommended to intentionally bend a rear axle unless you absolutely have to in order to save a car. Keep that in mind. The list above assumes ss axles; scout axles should be tuned and it is a PITA.

 

Thanks B Regal. I am using scout axles with set screws actually, but not sure if they are that practical yet. The stock axles are not pre-bent just using the SBE a 3 degrees.
Update, I actually didn't want to bother checking the rear align as I didn't want to risk potentially making things worse. So I adjusted the DFW weighting to 20.3ish grams and that stabilized things some. I even backed the steer off to 5/6 inches from 9 and narrowed the gaps on the wheels based on the others in the chat. I set the test track up inside the basement and this beat my previous supercar most times, though my starter gate is a 6inch furring strip.

 

What B_Regal is saying is the stock or “scout” axles that come in the box are bent already. You can’t see it because the bend is super slight but you can tell because if you turn your rear axles, your times will change. If you have a K house groove cut into it, then your going to want to start with them both faced up, turn one of the rear axles four times, running it each time you have them set. After all four quarter turns are done, turn the other side you didn’t turn one quarter turn and repeat, turning the first axle you started with four times, then turn your second a third, do the four turns and runs, then the fourth. The scout axles require you to run the car 16 times so you know where they run the best. When you know where they run best, you can then turn each side an eight if a turn or so to get the absolute best spot. The difference in the rear axles can be .01-.08 difference in speed, which is a lot!

Best way I can stress the importance of this trick is this. You can have a car with a perfect drill, perfect chassis, make fenders for it, have the weight perfect, have everything polished the right way and have it be well prepped with jig and oil but if the rear axles are out of tune and are not in the right position, it will lose to a car with toe in, weight randomly stuffed in the car, and running graphite. I’ve seen this firsthand in a scout race, it’s all in the rear axles.

Let me know if those steps are confusing. I can outline them better if need be, but if you have a track to test on, then this is a life saver. The 16 runs is why B_Regal referred to it as a PITA.

 

Even more of a PITA on a tuning board!! Lol

 

Is there an emoji for the sinking feeling? I need some time to process this as i just glued in ( daddy car) what i thought was straight axles...turns out i was wrong as it is veering 2 inches over about 4ft. Maybe i drill the glue out. It is 5min epoxy unless there is a solvent that works better.

 

Yeah, your going to want to stay away from gluing your axles in, Lol. Absolute worse case if there too loose then you can chip of a little piece of wood from a toothpick or something but that’ll still mess up your alignment. As for getting your axles out, see if you can just twist them out with axle extraction pliers or any pliers for that matter. Or did you already get them out and just have glue in your axle holes?