Phase II

The TXT-1 is an awesome truck from the box - it's currently the *best* production solid-axle monster out there. However, with it's centralized transmission, motors and batteries all up in the upper-chassis area, the truck is somewhat top-heavy. I also run the truck with dual-8.4 packs (read the full report on that here) so the 14-cells makes the rig even more tippy.

Making turns at high speeds would generally tip the truck over on two wheels. While looking cool, I decided to see if I could make a better high-speed handler out of my truck. What I wanted to achieve were:

In short, I wanted to retain the power and speed of the increased cells, but to improve the handling of the truck. So Phase 2 began...

Repositioning the Battery-Packs

I was always stumped when wondering how I could shift the batteries to a lower position. I couldn't mount them between the front and rear gearboxes like in a clod because the centre gearbox is there - in fact, that gearbox seemed to prevent shifting the batteries anywhere in the frame at all! Then I chanced upon my Emaxx and it stuck me - I could mount the batteries on the sides of the centre gearbox. I was running dual batteries so this would be a perfect solution.

In the pics you can see the simple mounts I made for the batteries - holes were drilled to relieve weight and battery straps were used to hold down the cells. The mounts are positioned to be as low as possible without getting in the way of suspension movement; at full articulation, the lower link bars come close to the batteries, but just miss them.

Repositioning the Electronics

Now with the batts out of the way, it was certainly simpler to relocate the electronics. I removed the two upper plastic decks and decided that I would move the electronics to where the batts used to be. Instead of sweating over an aluminum electronics tray which might interfere with the radio signals, I opted to use a plastic sheet that was not only easy to cut, it also made the chassis look cleaner because it was clear. I mounted the sheet to the rails with 4 zipties.

I found an innovative way to mount my antennae too! It's neat and it works

Lightening the truck

Removing the plastic decks removed some weight, but I also removed the front and rear bumpers to shave off a little more. Overall, the chassis looked a lot cleaner and more race-oriented too.

Other Modifications...

To improve steering, I added some spacers to lengthen the front lower suspension rods. This adds some castor to the front steering which helps the truck steer better. I also replaced the stock rodends with some I had in my toolbox which had much less slop.

After a lot of hard bashing, the stock universal shafts which link the 3 gearboxes were binding just a little bit at the telescoping part... so I decided to try a quick mod which I read about on some RCMT forums. I replaced the shafts with traxxas slider units meant for the Emaxx.

One last significant mod was to reverse the whole centre gearbox. In stock trim, the batteries (which are the heaviest part of the truck) were positioned in the rear of the truck and the motors (the second heaviest items) balanced them in the front. With the batteries now on the sides, the truck was now front heavy because of the motors. This would affect performance especially on jumps, so I reversed the centre transmission to position the motors to the rear of the truck. The motor endbells were also rotated 180 degrees to reverse their rotation.

For the purpose of these pics... I also decided to go for a more racer-like body. The TXT-1 and Emaxx body mount positions are identical so I just took my Emaxx rally-truck body and mounted it low.

Performance!

With a pair of freshly charged batteries, I took my "racer" for a spin!

When I nailed the throttle, the truck lurched forward into a wheelie, but the wheelie was certainly less "dramatic" than in stock trim. The lower CG was clearly apparent as the TXT was very much more sure-footed. I was doing full speed turns on high-bite tarmac and although it did raise it's inner front wheel at times, it never came close to flipping on it's lid. Note that "full speed" isn't slow either - I'm running 14x2 mod motors with dual 8.4volts 2000mah cells with 16-teeth pinions.

I took the truck climbing and it was more stable than previously. I intend to lower the truck by putting spacers in the shock bodies but since I had not yet done this, the truck still had it's not-at-all-shabby stock articulation. No flips today - hooray!

I was having a ton of fun on the climbs and even had a small crowd gathering when all of a sudden, I found I was only getting 2WD... a quick check showed that the rear traxxas universal had twisted badly and the yokes had come apart. Although the front pair still looks good, I decided to go back to the stock pair until I can find a better solution. At this point I also removed the blue booties because they actually made the joints very hard to access - I'll see how the joints hold up without the protection.

The truck is performing great and certainly handles better than before. It's still not the ideal racer though... some areas that still need looking into are:

I'm toying with the idea of an Emaxx tranny which would give me a slipper clutch and a 2-speed gearbox... but the tranny is loud and I don't really know if I need a 2-speed on this... well, maybe if a reasonably priced Emaxx tranny becomes available? :)

In summary, Phase 2 took a little thought but was easy to do... performance is far superior than stock with no negative results so far. It's also cool that my TXT is becoming more uniquely my own... most importantly, I'm having fun!

Before Pic

After Pic

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