Traxxas 4-Tec Conversion - Page 3 - RC-Monster Forums

BrianG · 03.20.2009, 11:19 PM

lol, it's not brushless yet, but since I don't plan on making any purchases in the very near future, I decided to slap the electronics from the Slash (XL-5, 12T titan, 6 NiMH cells). Obviously, it's pretty slow, but fine for in the house.

Here's where I ran into a problem. I wanted about 1/2"-3/4" chassis clearance to avoid the normal pebbles on the road. So, I modded the rear shock positions to get the back end higher. Then. to get the body to fit right, I had to lower the mounts. Unfortunately, the front upper shock mounts now got in the way, so I made a little cutout so they stick up out of the hood. Not the prettiest thing, but it works.

Since the Titan is so wide, I can only gear down to 15T, and it gets pretty warm - even warms the entire chassis! Oh well, the XL-5 and Titan are throw-away parts anyway.

BL_RV0 · 03.20.2009, 11:24 PM

Looks good Brian.

JERRY2KONE · **Cannot wait. -** 03.21.2009, 04:22 AM

I personally cannot wait to see some videos of this thing once you get some brushless in there and some really good Lipo cells. I have kind of wondered about the 4tech as a BL road-racer for a while now. Your opening the door for guys like me, so thanks BG. It is going to be great to see the BL version up against one of the nitro cars. Good luck with your project Brian.

BrianG · 03.26.2009, 07:22 PM

Hmm, I'm kinda torn right now.

I have enough spare parts to make a complete setup, but using a brushed motor (Titan 550 12T) but the belt arrangement creates a lot of drag. So, I was thinking of making this RWD only and keeping the Titan and XL5 ESC in there. Removing the front diff, shafts, belts, etc will make it quite a bit lighter and runtime will be better. 2WD will be harder to control, but the brushed motor doesn't have tons of torque anyway, so it shouldn't be too bad. This was never meant for a speed car anyway, so that's not a biggie.

If I went BL, I'm gonna have to wait for a motor.

BrianG · 03.26.2009, 09:40 PM

I decided to go the 2WD route. Right away, I noticed it is faster and not any harder to control (at least in the basement). And the motor and ESC don't get as hot as fast. I think I'm gonna keep it this way. Fun for around the yard. If I want to go fast, I'll pull out the GTP...

lydiasdad · 03.27.2009, 11:25 AM

i run a 12t titan on 4s a123 in a tt-01 with good results. it's slightly slower than the mm 8s fiego on 3s a123. just have to not over gear. the titan pushes a staduim truck to 30mph on 6 nimh cells. its a good bahsing setup

BrianG · 03.27.2009, 11:51 AM

Yeah, it seems to go pretty good, considering.

Since the Titan on 4s A123 is roughly the same speed as an 8s on 3s A123, that means the kv of the Titan is around 3100. So, since I'm running 6 NiMH cells geared 45/15 in the 4-tec, that puts my top speed right around 32mph. Not high for an on-road car, and certainly a lot slower than stock, but fun for around the house bashing.

The only thing I don't like about the XL5 ESC is the piss poor brakes (and I did recalibrate the ESC to the radio). Having little experience with brushed motors, I don't know if this is the ESC's or the motor's fault. I may just throw in a spare MM/BEC setup so I can get better programming, and the ability to run 6 cells or 3s. Just gotta set it to brushed mode. Plus, if I decide to get a BL motor in the future, it'll be plug-n-play for the most part.

lincpimp · 03.27.2009, 11:59 AM

I run a pair of the 12t motors in a tamiya blackfoot, with front and rear trannys. I use a novak super duty on 3s lipo and it is geared for about 34-35mph. The rear motor does get warmer than the front, but I use a clip on heatsink to equalize the temps a bit. I have to run the motors without the slide on can wrap metal thingys (technical term, sorry about that for the noobs) as they are a tight fit in the trannys.

Great setup, and the novak esc has great brakes. It will do wheel stands in either direction. and I can run a low rate lipo, 18c 3000 (maybe not that low) and get 1/2 hour runtimes at least. I like the 12t motors, work well for me.

BrianG · 03.27.2009, 12:12 PM

Yeah, I think the Titan will work fine for what I'm looking for. For me, high speeds=high repair bill.

But, changing over to 2WD is the best thing I could have done. Not only is it lighter and a LOT less drag, but I now have a spare diff and axles for the rear.

lincpimp · 03.27.2009, 01:13 PM

Quote:

Originally Posted by BrianG

Yeah, I think the Titan will work fine for what I'm looking for. For me, high speeds=high repair bill.

But, changing over to 2WD is the best thing I could have done. Not only is it lighter and a LOT less drag, but I now have a spare diff and axles for the rear.

I tried to run mine 2wd... Wow, it was insane. The setup I run seems to need 4wd. As for the axles and diffs, they are holding up fine for me. I really doubt they will wear out quickly, but it is always good to have spares. I bet you removed a fair amount of weight doing that, 2 belts, the diff, front transfer shaft, driveshafts, etc. It all adds up.

What body do you plan to run?

BrianG · 03.27.2009, 01:45 PM

I'm sure with a lot more power, it would NEED 4WD. If I go BL, I might just get a Medusa 36-50 or similar. There was quite a bit weight removed; just the diffs and top shaft alone were quite heavy. But the biggest savings was drag removed. Put it this way, with 4WD, I almost didn't need to apply the brake at all. With 2WD, the XL5/Titan doesn't have enough braking force at max.

Stock body. Call me easily amused, but I rather like the way the stock 4-tec body looks.

lincpimp · 03.27.2009, 01:48 PM

Quote:

Originally Posted by BrianG

Stock body. Call me easily amused, but I rather like the way the stock 4-tec body looks.

I kind of like it too, but prefer the old 2.5 body a bit more. Looked more exotic.

TheRandom1 · 03.27.2009, 02:40 PM

Wow this is a pretty darn cool build!

BrianG · 03.30.2009, 01:46 PM

Update:

Speed on 2s is pretty poor outside. Maybe 20mph with a tailwind. So, I then tried the XL-5 on 3s lipo. Much better. Seems to handle it ok, but didn't want to take chances, so I put my spare MM/UBEC and configured it to brushed mode. Even with the MM brake force at 100%, it hardly works. Actually, I can hardly see any difference between full brakes and just letting it coast to a stop. Can the Titan motor really be that bad? I disconnected the motor and spun it by hand with the wires touching and then not touching. Almost no brake effect.

Looks like I'm gonna get a motor sooner than I thought! Probably will settle for a Medusa 36-50-3300 or 36-60-3100 on 3s.

KMN · 03:57 PM

Yes, the titan 12T's are that bad.

Small, hard, enclosed brushes = NO brakes. No matter what controller you use.

EDIT -

On a second look, are the .3uf caps soldered onto the motor? No brushed motor will brake well without them.