Limitless Drag setup issue

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jondilly1974

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Arrma RC's
  1. Granite
  2. Infraction
  3. Kraton 6s
  4. Kraton EXB
  5. Senton 3s
  6. Typhon 6s
  7. Typhon 3s
My stretched Senton drag setup that started out as a Typhon, stretched with a Mojave chassis, then swapped to Senton width, Limitless towers and shocks, and now Limitless body, seems to kick out the rear end on a drag hit at right about 132ft. It leaves real straight no problem. But at higher speeds it seems like the rear end is overdriven. Center is a spool. Front and rear are GP4 EXB diffs with aluminum locker inserts. Tires were Sweep Max Forward, matched set. I have a small rear wing for rear downforce. Trimmed Limitless winglets up front. Shocks are travel limited via fuel tube bump stops. Can’t figure out why the rear end whips out like this. I will post a short vid here in a little bit.

62F02135-2B03-4404-8E54-D686F941E97D.jpeg
 
Here is a quick video of the issue.

I can see in your slow mo section of the video it is stepping to the right up until the big end and then swings the other way which is when it spins out.
How is the center diff setup? Maybe thinner would help the front tires lead the car more?

No expert in drag at all but trying to assist in thinking through the possibilities.
 
I can see in your slow mo section of the video it is stepping to the right up until the big end and then swings the other way which is when it spins out.
How is the center diff setup? Maybe thinner would help the front tires lead the car more?

No expert in drag at all but trying to assist in thinking through the possibilities.
Center is a spool as Jon said, so that's not going to be it. I observed the same thing you did; the car never appeared to be driving in a straight line from the jump. I'm kinda with @K-BASH on trying a larger rear wing which should help with keeping it on track as speed increases. Maybe something with large side winglets for more directional stability than downforce? Just spit balling here.
 
Well the spool let go today on my first test hit, so it will be a few days before I can try again. I wish I could find that red Loctite that Arrma uses. I clean my parts with alcohol and let them dry, then apply TL, assemble and wait at least 24 hours and spools rarely hold together for long.
 
+1 on increasing the rear wing. The aero drag won't harm the time but will help with the traction and might help it shoot straight.
I think a center diff could be helpful for tuning the font vs rear traction.

I would be willing to bet if you unlock the rear diff it might help it stay straight.
 
+1 on increasing the rear wing. The aero drag won't harm the time but will help with the traction and might help it shoot straight.
I think a center diff could be helpful for tuning the font vs rear traction.

I would be willing to bet if you unlock the rear diff it might help it stay straight.
From my own limited experience with drag hits, I liked the cars behavior better with a center diff as opposed to a spool as the power distribution felt notably, and probably not surprisingly, more balanced. To be fair, I've never spent a large amount of time trying to tune the car to a center spool so my experience is anecdotal at best. Another thing that seemed to improve the durability of my spool setup was after moving to Kullagrossisten gears and replacing the stock grubs with M5 Torx® grubs. I only use low duty Loctite®242 and I don't even let it cure overnight and I have yet to have the spool let go on me...although, it's probably also worth mentioning that I haven't been running any high power 6 or 8S rigs, so I'm sure that will also factor into the equation.
 
Increase the preload on the rear right spring or you could try a softer weight oil to help weight transfer a bit. It’s definitely a suspension thing. Well would be in 1 to 1 cars I would assume it would transfer over.
 
+1 on increasing the rear wing. The aero drag won't harm the time but will help with the traction and might help it shoot straight.
I think a center diff could be helpful for tuning the font vs rear traction.

I would be willing to bet if you unlock the rear diff it might help it stay straight.
Without a locker in the rear, it thins out real quick and ends up diffing out badly. A rear locker is a must IMO, the center and front I could debate.
Increase the preload on the rear right spring or you could try a softer weight oil to help weight transfer a bit. It’s definitely a suspension thing. Well would be in 1 to 1 cars I would assume it would transfer over.
I have them setup as solid links using a bump stop, so there isn’t really any adjustment to make. However I have sets of turnbuckles on the way so I can tune the lengths.
From my own limited experience with drag hits, I liked the cars behavior better with a center diff as opposed to a spool as the power distribution felt notably, and probably not surprisingly, more balanced. To be fair, I've never spent a large amount of time trying to tune the car to a center spool so my experience is anecdotal at best. Another thing that seemed to improve the durability of my spool setup was after moving to Kullagrossisten gears and replacing the stock grubs with M5 Torx® grubs. I only use low duty Loctite®242 and I don't even let it cure overnight and I have yet to have the spool let go on me...although, it's probably also worth mentioning that I haven't been running any high power 6 or 8S rigs, so I'm sure that will also factor into the equation.
Surprisingly this car is a 4S car but it is using a TP4070 2250kv which is super torquey.
 
My 1/10 noto requires lots of rear wing or rear steps out at 60ish everytime same speed..more wing solved it.
Pretty funny is that's about the speed it happens. Maybe it's because I am used to a rear diffuser on most of my cars that hit that speed. I will do a bigger wing next rip.
 
Pretty funny is that's about the speed it happens. Maybe it's because I am used to a rear diffuser on most of my cars that hit that speed. I will do a bigger wing next rip.
I even tried running noto with defuser and no wing,,,,big mistake....azz was like being on ice at far less than 60..what shore Sweeps you like most for drag??sale on 25shore gt8 contacts,softest they offer...do they wear super fast??
 
I even tried running noto with defuser and no wing,,,,big mistake....azz was like being on ice at far less than 60..what shore Sweeps you like most for drag??sale on 25shore gt8 contacts,softest they offer...do they wear super fast??
If you use tire sauce with foams they almost don't wear at all. It's pretty remarkable. I use Contact 35°Sh for speed running and I'm getting great mileage out of them.
 
I even tried running noto with defuser and no wing,,,,big mistake....azz was like being on ice at far less than 60..what shore Sweeps you like most for drag??sale on 25shore gt8 contacts,softest they offer...do they wear super fast??
I am running the Max Forward Soft and they hook pretty well. But they do wear out on rough pavement. Not as fast as a set of Hoons but pretty quick. They chunk out if you turn at high speed and slide.
 
Never had that issue with my Infraction. As long as it takes off straight, it stays straight...which is really just a matter of getting the rear shocks dialed. It has never stepped out further on down a run.

@jondilly1974 I'd try putting shocks back on the vehicle, at the very least in the rear. I think you might be screwing with the cars capacity to transfer weight under acceleration. Again, just spit balling. Where's @phildogg when you need him? :LOL:
 
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