Limitless Anatomy of a Center Spool

[kaladeth]

I will post the different center spools I’ve had a chance to run on the Limitless V2. I will also include a center diff option once I get to try it out (already have the diff but do not yet have the appropriate drive shafts).

1. SpeedTek RC
2. Modified Arrma Spool Set ARA311070
3. (planned) Scorched Trident Centre Drive Shafts and Spool
4. (planned) IRonManRc Arrma Limitless V2 Titanium Center Spool
5. Infraction 6S Center Differential

1. SpeedTek RC
https://www.speedtekrc.com/product-...liminator-heavy-duty-speed-spool-complete-46t

This is a convenient drop-in spool without having to worry about spacers.

The center grub screw got loose after only the first few runs so worth checking on arrival (I should probably do this on everything). I used red loctite and torqued it down but after race day 2 found it was loose again… may be due to the shaft groove (see below). The four cup grub screws were tight.

The front-side cup also has deformed a little bit increasing the slop on the front dog bone. Not sure yet what caused this - too much sudden acceleration maybe? It’s a 2028 1100kV can. But why is the back cup ok?

The shaft also seems to be made of soft metal, you can see the grub screws making circular grooves. I ordered one more with a raw steel shaft - will see if it fares better.

Lastly, the spacers seem to place the spur gear a little bit more forward of the bottom chassis slot, so don’t count on going any bigger than 46t. The gear is also thicker than stock just FYI.

Other than that a pretty decent option when you need one in a hurry.

 

[Diem Turner]

I will post the different center spools I’ve had a chance to run on the Limitless V2. I will also include a center diff option once I get to try it out (already have the diff but do not yet have the appropriate drive shafts).

1. SpeedTek RC
2. Modified Arrma Spool Set ARA311070
3. Infraction 6S Center Differential

SpeedTek RC
https://www.speedtekrc.com/product-...liminator-heavy-duty-speed-spool-complete-46t

View attachment 351583

This is a convenient drop-in spool without having to worry about spacers.

The center grub screw got loose after only the first few runs so worth checking on arrival (I should probably do this on everything). I used red loctite and torqued it down but after race day 2 found it was loose again… may be due to the shaft groove (see below). The four cup grub screws were tight.

The front-side cup also has deformed a little bit increasing the slop on the front dog bone. Not sure yet what caused this - too much sudden acceleration maybe? It’s a 2028 1100kV can. But why is the back cup ok?

The shaft also seems to be made of soft metal, you can see the grub screws making circular grooves. I ordered one more with a raw steel shaft - will see if it fares better.

Lastly, the spacers seem to place the spur gear a little bit more forward of the bottom chassis slot, so don’t count on going any bigger than 46t. The gear is also thicker than stock just FYI.

Other than that a pretty decent option when you need one in a hurry.

View attachment 351577

I suspect the front cup is worse for wear because the front drive shaft bisects the bulkhead at an angle due to the kick-up in the front. That's why Scorched started making the Trident front shafts to ameliorate that issue. The rear drive shaft is straight and level resulting in less strain, wear and tear.

 

[kaladeth]

2. Modified Arrma Spool Set ARA311070

For the cost of the (larger) spur gear and a few spacers you can just modify the stock spool.

You might also need to file down some sections for the grub screw to seat on. Details on spacer lengths I used for this particular 46t spur:

https://www.arrmaforum.com/threads/...echnical-race-build.67901/page-4#post-1048501

Works like a dream, will update this post in case I encounter issues in the next few races.

 

[kaladeth]

3. Trident Centre Drive Shafts and Spool Complete Set - for Arrma Limitless / Infraction /Felony

https://scorchedparts.co.uk/product...um-centre-drive-shaft-and-pinocchio-spool-set

(planned)

4. IRonManRc Arrma Limitless V2 Titanium Center Spool *BEAST*

https://islandhobbynut.com/products...enter-spool-beast?_pos=2&_sid=28780a786&_ss=r

(planned)

 

[kaladeth]

5. Infraction 6S Center Differential
https://www.arrma-rc.com/en/product/center-diff-set-46t-100k/ARA310989.html

I did the math for the Center Diff. It is not a straightforward install. The dog bones will have to be custom.

Stock Spool Set (V2)
116 mm + 112 mm + 116 mm = 344 mm
- AR310472 - DOGBONE 116mm (2pc)

Center Diff Set (Infraction)
102 mm + 68 mm + 168 mm = 336 mm

- ARA310941 DOGBONE 102mm (1pc)
- ARA310942 DOGBONE 168mm (1pc)

Center Diff vs. V2 Spool
12 mm + 68 mm + 32 mm

Dogbones Needed
128 mm and 148 mm

 

[Dan B.]

5. Infraction 6S Center Differential
https://www.arrma-rc.com/en/product/center-diff-set-46t-100k/ARA310989.html

I did the math for the Center Diff. It is not a straightforward install. The dog bones will have to be custom.

View attachment 354541

Stock Spool Set (V2)
116 mm + 112 mm + 116 mm = 344 mm
- AR310472 - DOGBONE 116mm (2pc)

Center Diff Set (Infraction)
102 mm + 68 mm + 168 mm = 336 mm

- ARA310941 DOGBONE 102mm (1pc)
- ARA310942 DOGBONE 168mm (1pc)

Center Diff vs. V2 Spool
12 mm + 68 mm + 32 mm

Dogbones Needed
128 mm and 148 mm

Obviously it would be a PITA, and also eliminate one of the best features of the V2, but if you were to move the motor mount a bit you could take advantage of a standard length dogbone on one side, thus only requiring one of custom length.
OR, if you’re having custom stuff made anyway why not have some hardened output shafts from the diff made to fit the V2 stock center shafts? You would then have a Pinocchio diff! That’s the way I would probably go, as you could then run the best *available* center shafts of your choosing.

 

[Diem Turner]

5. Infraction 6S Center Differential
https://www.arrma-rc.com/en/product/center-diff-set-46t-100k/ARA310989.html

I did the math for the Center Diff. It is not a straightforward install. The dog bones will have to be custom.

View attachment 354541

Stock Spool Set (V2)
116 mm + 112 mm + 116 mm = 344 mm
- AR310472 - DOGBONE 116mm (2pc)

Center Diff Set (Infraction)
102 mm + 68 mm + 168 mm = 336 mm

- ARA310941 DOGBONE 102mm (1pc)
- ARA310942 DOGBONE 168mm (1pc)

Center Diff vs. V2 Spool
12 mm + 68 mm + 32 mm

Dogbones Needed
128 mm and 148 mm

You know what might be worth a shot, contact David at Scorched RC. He makes dog bones for all the different Arrma platforms and maybe he'd be so kind as to put those two together for you as a set.