Traxxas 4-Tec Conversion

[_paralyzed_]

I'd take a castle over feigao. get the 4600 castle?

[BrianG]

Ugg. The 4600 is an "ok" motor, but is really smaller than a true "S" size motor because of the space taken up by the coil wire to noodle wire connections. If CC had a series of motors that were 60mm long, that would work I think; the kv and can size (torque) would be a better match for this setup. Besides, this is geared kinda high and I'll need the extra torque that a slightly longer motor will provide to get going; either that or go with a slotted stator type in a shorter can.

[_paralyzed_]

My buddy has been torturing his 7700 in his rustler with 3s 20c 5000mah zippys. Burnt up two sidewinders, numerous drivetrain issues, but that motor keeps taking it. Your right about the smaller size. I just can't see an "s" feigao over a castle. an l or xl, sure, but I'd put the cc motor over the s feigao anyday.

[BrianG]

Well, it's done!

I ended up ditching the front drive and totally re-doing the layout. This allowed for much better weight balance - now the center is only about 5mm off center! Aside from the batteries, all the other components are as far right as I could make them.

Total parts list and other points of interest (taken from my BL Conversions page because I'm lazy):

• Spektrum DX3r Radio
  
  
• Mamba Max ESC with the BEC disabled
  
  
• Dimension Engineering ParkBEC
  
  
• Medusa 36-50-3300 motor with added heatsinks
  
  
• Elite 3s 30C 3300mAh lipo battery
  
  
• Geared 45T spur, 15T to 26T pinion depending on desired speed
  
  
• Modified the chassis around the spur gear to allow easier gear changes
  
  
• Custom 6061-T6 aluminum motor mount
  
  
• Custom 6061-T6 aluminum top plate
  
  
• Custom 6061-T6 aluminum battery tray with lexan shield for the bottom of the battery
  
  
• Custom 1.5mm thick aluminum shield under the rear differential to protect against rocks
  
  
• Servo mounts from an Xray XT8 to mount the steering servo
  
  
• Front toe links from an Xray XT8 for the steering linkage
  
  
• Rear wing stay from a Mugen MBX5r for one of the top plate standoffs, the rest are custom cut 6061-T6 aluminum tubes
  
  
• Turnbuckle from the Traxxas Jato for a chassis brace
  
  
• Converted to 2WD to allow better placement and balance.
  
  
• Upgraded to Traxxas steel outdrives
  
  
• Upgraged to Traxxas aluminum rear axle carriers
  
  
• Moved steering assembly to the other side for more even balance
  
  
• Moved rear shock mounts to the same bolt as the body mount to allow for more ground clearance.
  
  
• Removed first gear and modified the two speed hub to be locked into second gear to enable motor braking and reverse

Anyway, here are the pics:













This last one just showing the weight balance. I don't have a scale, so a thin piece of wood will have to suffice.

[nitrostarter]

Any runs with the BL yet? I'm curious how the 2wd will handle the power... Looks great tho!!

[BrianG]

I just finished it tonight so no runs except for in my basement. Even with 100% punch control, it lights up the tires easily. Donuts are easy. Not sure how it does at high speed yet; if it's nice tomorrow when I get out of work, I may take it for a spin and get a small video.

Before I got the Medusa motor in, I threw in a spare CC 5700 motor I had laying around. It worked fine, but not as smooth as the Medusa and it heated up pretty quickly even geared as low as I could (45/14). The Medusa is geared 45/15 and never got even luke warm.

[BrianG]

I ran it for a while today. As expected, the back end is a little squirrely. Did some high speed runs and without a GPS or radar gun, it's hard to tell the exact top speed, but it's close if not over the calculated value. The 3s lipo retained over 3.7v/cell for around 3-4 minutes, so that helped. To get the thing under control, I did some burnouts/donuts/drifting to heat the tires up. Worked too; got them up to 127*F. After that, traction was a TON better and had much better control. The road in front of my house has a crown (uneven at that), not to mention a manhole cover, so getting it to steer perfectly straight was impossible. Still pretty fun though.

Temps were good: barely over ambient (65*F) for the batteries, 108*F for the motor, and 113*F for the ESC. Not bad for extended speed runs. Those clip-on motor heatsinks had partially came off and had a ton of sand/grit between them and the motor; so they were actually insulating the motor rather than cooling it. I bet the temps would be better if they were actually mounted right. I'm gonna tack them on with some thermal adhesive to keep them in place, yet not so much that I can't take them off if I want.

The 3s 3300mAh 30C elite batteries help up great. Like I said, they held higher voltage for quite a while. I'm not running the LVC since I use 6 NiMH cells or 3s lipo depending on if I'm in the house or outside. When I noticed a drop in power/speed, I stopped. Two minutes after stopping, the voltage was 3.32v/cell. A little lower than I like to run, but I'm sure they would drift back up more to a more acceptable ~3.5v/cell after 15-20 minutes unloaded.

Runtime was a hair under 25 minutes, which puts average current draw at ~8A. Given this is 2WD, low vehicle weight, and limited traction, I can't see this setup drawing more than 50A bursts.

Putting them on the charger, they only took in ~400mAh before they reached 3.8v/cell. The voltage was pretty steady after than until the last 600mAh as they rose to CC/CV threshold. Seems these are decent cells. Probably not good for 1/8 scale, but perfect for 1/10 2WD applications.

[BrianG]

Anyone know where I can get wider tires for this thing (rubber, not foam)? I have some foams that it came with, and they are a good 5mm wider, but are wearing out fast. They work quite well though. Something with about the same wear rating as the stock trx slicks would be fine, just wider for a little better grip.

[mjderstine]

if it takes 12mm hex, you can get the HPI 26mm rims and rubber, just check out tower, or amain, or stormer.
http://www3.towerhobbies.com/cgi-bin...&I=LXM981&P=SM

[magman]

Nice clean layout Brian

[BL_RV0]

Looks great Brian.

[BrianG]

Thanks guys.

mjd: I saw those but wasn't sure they'd be "solid" enough. I think I saw those at my LHS and they felt too "squishy" and would balloon badly, especially given the extra width. The foams in the stock tire is denser (or maybe the rubber is thicker), so they don't balloon as badly. For the price they want for tires, you'd think there would be more to it than simply molded rubber.

[prhess]

Originally Posted by BrianG

Anyone know where I can get wider tires for this thing (rubber, not foam)? I have some foams that it came with, and they are a good 5mm wider, but are wearing out fast. They work quite well though. Something with about the same wear rating as the stock trx slicks would be fine, just wider for a little better grip.

I have been using these on a tamiya F201 car and my 4-tec. They work well, the great thing is they use 12mm hexes

fronts 30mm foams
rears 40mm foams.



made by Kawahara - great name in tires.

I have only ordered them from Hong Kong, but Mugen is the distributor in the US.

They come in many shores 35, 37, 40, 42.

Egr mart in Hong Kong is where i have ordered from

http://www.egrracing.com/shop/sponge...9_196_194.html

Kawahara website description

http://kawahara-racing.co.jp/Ekawa.html

Enjoy

[BrianG]

Cool! Thanks.

[PBO]

How about these ones...

BSR

I believe they custom make for speed runs also