Friday, 27 May 2016

Mod: MTB "Reapers" in an RS

MTB "Reapers" (name coined by Foam Data Services) are a prototype 2S 180 motor that hasn't (yet) been put into production. These samples were sent to Ryan of MTB along with samples for the MTB Hellcat, which should be arriving in the next few weeks. I acquired a pair of the Reapers, with the other pair being sent to FDS. I installed them in my 2S LiPo RS rifle.
For comparison, Blade 180s/-3240s (reference) spin at ~32kRPM and produce 429gcm at 7.4V, drawing ~22A at stall. These MTB Reapers spin at 44.4kRPM and produce 735gcm of torque at 7.4V (rated 36kRPM, ~600gcm at 6V), drawing ~45A at stall. The specs are absolutely insane, but also are sub-optimal for use on 2S as a flywheel motor. As I detailed in my post about MTB Honey Badgers, 36kRPM at 6V is quite excessive for flywheel use as it is well above the "glass ceiling" speed for single stage flywheels, and so is quite wasteful and unnecessarily loud.
Something I wanted to try was Worker wheels at high speed. As I mentioned in my Worker flywheel review, one of the guys in our Melbourne groups runs XP180s on 3S with Worker wheels in his RS and has reported significant muzzle velocity gains over 2S. XP180s on 2S is already reaching glass ceiling speed, so XP180s on 3S using conventional flywheels should have no significant gains, and will probably start melting darts. Worker flywheels seemed to prevent this dart melting as the RS in question gets quite a lot of use in Melbourne events and works really well.

I used this RS for a couple of rounds in the most recent MLF and it worked quite well. In terms of muzzle velocity, it was beating my Bullpup RS by around 10-15fps on average (both using FVJs), and thanks to the monstrous torque, spun up to full speed about as fast as Blade 180s/-3240s on 2S. In my testing with my Kooshes, it beheaded darts even more frequently than my Bullpup with Worker wheels did, tearing through even the better glued darts, including a few of the Gen 3s. I would definitely stick to very robust darts like FVJs for Reapers with Worker wheels.
Initially, I left my RS rifle on a Blade 180/-3240 pusher, however I found it to be rather slow for my liking, especially seeing as I regularly primary a Bullpup RS that does ~12dps at full charge. I decided to pick up another MTB Honey Badger for use as an RS 2S pusher, as although it was intended for a high speed 3S pusher, even on 2S it outspeeds just about every other 2S suitable motor I know of (besides Reapers, which are rated at 1kRPM more at 6V). Unfortunately, as I'd set up the pusher box for 180s, the Honey Badger tended to pop out of position after a short amount of use. I decided on a new course of action - switch the flywheel motors back to Blade 180/-3240s and the pusher to an MTB Reaper. The Reaper is rated for about the same speed as the Honey Badger, yet sports around 2.5x the torque. I wanted to switch the flywheel motors back to 3240s not just because I only have 2 Reapers, but also because I wanted to try the setup on both 2S and 3S, and Reapers on 3S would be completely and utterly insane as flywheel motors. Additionally, Blade 180/-3240s on 2S are much more usable with Kooshes than Reapers.

The results are nothing short of insane. On close to nominal 2S voltage (~7.67V), the MTB Reaper yields a ROF of around 11dps, suggesting a full charge (~8.4V) speed of around 12dps. On near full 3S voltage (~12.51V), it achieves a ROF of around 17dps, or around 1000rpm. I do question the Reaper's longevity on 3S though, so will be keeping the RS Rifle for 2S usage only. Even then, it matches the ROF of my Bullpup Rapidstrike, which I already thought was pretty darn fast. I did have to rewire for "dead centre" again though, as even on 2S the pusher is travelling way too fast to stop without overrun.
Personally I think MTB Reapers are a bit excessive for general use. They are substantially faster than Blade 180/-3240s, which themselves are at a perfect speed for flywheeling, and decent for pusher duty. While I wouldn't mind a little more speed than Blade 180/-3240s (say 33-35kRPM at 7.4V), the 40kRPM+ at 7.4V of Reapers at 2S make them unnecessarily loud, much more dart damaging and almost uncontrollably fast as pushers. The sheer amount of current they draw also means MOSFETs should be a serious consideration for your rev switch. A pair of Reapers will draw more than 90A at 7.4V, which is completely ludicrous. While I personally like high ROF, overall I would far prefer that if MTB were to come out with a 2S intended 180, it was much closer in speed to the Blade 180/-3240. It would just be far more useful overall.


  1. Any additional specs on the reapers?
    any significant wear on the worker flywheels
    in particular where the shaft meets plastic?

    1. 36kRPM at 6V and 735gcm stall torque at 7.4V are the only specs I'm aware of for the Reapers.
      As far as I can tell, no extra wear on the Worker flys, however I only used it on 2S. I've heard of people having issues with XP180s and Worker flys, but those issues seem to occur primarily on 3S, where XP180s would be achieving around 50kRPM or more.