myteemouse

so i picked up a wind hobby ferret last year. (aka redcat racing electric tremor aka himoto exb) for $50 RTR. followed and contributed to the official thread, yada, yada, yada... over time everyone figured out that the drive pinions couldn't really handle a brushless motor; steel gears or a clutch was needed. but no one makes aftermarket parts specific for this car, and no one was really sure what could be adapted.

well, i adapted a clutch from the trinity now. i had to modify the chassis to do it though. i actually designed 2 chassis, one that just flips the motor mount around, to use a center spur (i call it the mark3 or mk3); and a second chassis that uses saddle packs for better weight balance (i call it the mark4 or mk4). the mk3 chassis is better suited to lipos, but i'm not ready to buy any yet (but i am pretty close). the best part is almost all the parts for the mod can be done using parts from a second ferret.

i built the chassis out of 2.3mm carbon fiber i got from mcmaster-carr. i originally intended to use fiberglass, but found carbon fiber sooner. aluminum can also be used. since i was designing a new chassis, i thought i'd try some other mods as well. i mounted the shocks inboard to protect them in head-on collisions, or rear impacts. inboard shocks also help centralize weight to provide quicker handling (not sure i noticed a difference in handling, but the front shocks have survived many impacts). the front shock mod needs the arms from the monster truck/atv version of the car. i also designed new shock towers out of aluminum (from k&s) because the oem are kinda soft; the aftermarket shocks i bought are shorter than oem, and i wanted to be able to adjust roll center.

i guess you could call this the franken-ferret? anyway, i'm posting posting pics and all, as a sort of how-to.

first, the chassis designs:

myteemouse

since i decided to build the mk4 chassis, this thread will follow that build. i didn't mock up the mk3 chassis, but the transmissions are the same. the design uses a dog bone to drive the front gearbox, and a modified main shaft to drive the rear gearbox. both gear boxes use the front drive pinion, instead of two different pinions. for the mk3, the motor mount will have to be used backwards (something i didn't want to do.

here's a mock up, and an installed tranny. the rear shaft is supported by a rear hub carrier from a second ferret, and 2 bearings (had to buy those). the shaft is covered with heat shrink so the batteries won't short out on it, and to shim the shaft to the bearings, since the shaft is just a little too small.

ferret owners will hopefully be able to make sense of the cad drawings above, as well as pics. if not just let me know, and i'll do my best to explain.

the first pic is the mock up over the cad drawing, the second pic is the actual build. my measurements worked out pretty well, as i was able to fit everything as planned. i did end up moving gearboxes towards the front and rear to make the center shafts fit. the wheel base grew by about 4mm or so. i suppose i could have just cut the rear shaft shorter...

i ended up flipping the spur around from the mock to the final build. it makes the clutch easier to access...

myteemouse

here are a few pics of the build....

myteemouse

here's the completed build:

myteemouse

yeah, i know, the final design looks like an ae b44, hot bodies d4 or tek18. i figured out i could have just left the servo on the right front side of the chassis, like in the original car. but moving the motor to the left side meant having to flip the motor mount backwards to do it. since i didn't want to flip the motor mount around i went with this design.

i see now why saddle packs are a really good design. they make it really easy to centralize mass (which makes a car handle much better). i know saddle pack lipos are available, but don't want to spend that kinda money. the other problem with lipos, is the fact that they're so light, they will throw off the balance of the car. saddle lipos will probably make the car too front heavy. right now, the center of gravity is just aft of the geometric center and maybe a little to the right (probably cause the motor). so, it should jump fairly level.

i think i might have figured out a way to make small lipos like the evolite fit, though. not sure if i wanna put the effort in to build it though, seeing as how i just finished this one. i can probably design it, and throw it up here if someone wants to try.

anyway, i'm running an ammo 28-35-5100 motor, 6 cell tenergy nimh, cc sidewinder micro esc and airtronics radio, rx and servo. i'm using internet rc/trinity now shocks with ae 6494 green springs (f/r) and ae 30wt oil (f/r). i'm able to run a robinson 19t pinion and oem 50t spur, and get about 10 min run times. temps stay under 150* for all electronics so far, running on dusty hard pack and street. mostly bashing right now, but hope to take it to a track soon, to see how well it jumpsand handles. running oem tires, duratrax d-bars mounted to hpi wheels, and xtm rage mt tires on hpi wheels.

need to mod and paint up a new buggy body. considering trying to build an 8 cell, just cause i can.

hope y'all like it..

myteemouse

here's some video:

http://www.youtube.com/watch?v=0Yeh8fjH4zQ

http://www.youtube.com/watch?v=UeayCKTnIGM

IloveMYxt2

Very nice build. Good work.

That thing would be sweet with a brushless motor and some lipo's

The_Lost_Otter

COuld you post a few pictures from the Macro Box you used?
You did a great job with the car.

myteemouse

thanks for the compliments.

yeah, the ammo motor's really quick. i'm sure it'll be even faster when i decide to get some lipos. its the first brushless motor i've ever used, so i'm not sure how it compares to others. i know a lot of the vendetta guys use the 3900kv version of the ammo motor, or the neu motors. don't really wanna spend the money on a neu yet, and it seems like it would make the car uncontrollable. maybe when i get a little more time under my belt i'll try a hotter motor.

the_lost_otter,
i'm not sure what you mean by Macro Box. could you please explain...?

The_Lost_Otter

This.
Or maybe you just placed some paper around for the pictures?
http://www.flickr.com/photos/archiej...nt/2744272893/

myteemouse

ohhh.... i didn't know that was called a macro box... interesting. i'd seen it called a photo booth or something...

anyway, yeah, for the photos i just used white poster board with a matte finish. it is propped up against something from behind. i just made sure it was big enough to cover everything behind it, and i shot as tight as i could without causing too much distortion. i didn't use any flashes or gels. i made sure to set the white balance on the camera (a point and shoot) for the overhead lights in the room, and let the camera somewhat overexpose the image because all the details in the black parts were getting lost at automatic exposure.