Some improvements on the DT-02 chassis

After the second run, I finally received the parts to hop up this buggy.

• ball bearings:
  You need 14 type 1150 bearings to fully ballrace the chassis. This requires to disassemble the gearbox and the rear drivetrain but this takes less than one hour to complete.
• hydraulic dampers:
  You need 50519 units at the front and 50520 units at the rear. The manual shows you should use the 2 hole piston at the front and at the rear. After some tests, the good choice is to use the 2 hole piston for the front dampers and to add the biggest spacer. At the rear, I advise you use the 1 hole piston, stiff springs and to add the 3 spacers so the damper is a little bit stiffer than shown on the manual. This setup makes the front drivetrain soft enough and reduces the rear drivetrain from sitting down so often. Apart from that, I chose to replace screws fixing the dampers with ball connectors: I'm not sure whether it is an improvement, but I prefer the look.
• the motor and the electronic speed controller:
  This chassis deserves a better motor than the stock 540 Mabuchi. After some hesitation on installing a Sport Tuned motor and keeping the TEU-101BK speedo, I finally chose to install a 23 turns Super Stock BZ motor (53930) withe the new TEU-302BK speed controller (45028). This one is rated to 23 turns motors on Tamiya sites, but rated 17 turns by Tamiya German agent. This difference in specifications is quite surprising. Anyway, the 302BK setup is easy to perform, like the 101BK's: actually, it is the exact same procedure

Photos of all this:

The TEU-302BK speed controller is not a new product but it is still unavailable in several countries (France for example). It is meant to be better than the TEU-101BK that Tamiya includes with almost all its models. The 101BK deals with motors up to the Sport Tuned with is rated 27 turns everywhere but in Europe where is it rated 23 turns. So far, I could not find the slightest information on either how to differentiate them nor to confirm that difference. For sure, a Super Stock BZ motor (23 turns) will make the TEU-101BK cut after a few minutes of intensive use. So the limit of the 101BK is over 23 turns.

It would be very surprising that Tamiya would produce a speed controller which limit would be "only" 23 turns because the difference with the 101BK would be too small. Nevertheless, this is what it is rated on official Tamiya sites such as the american subsidiary. I don't believe Tamiya would produce a speedo with specifications changing depending on the market where it is sold: so the 17 turns limit announced by the German agent seems logical. What is not logical at all is that the information is not the same depending on sources.

First runs

It rained all week long so the track was wet. As usual with XB Pro models (at least those I tried), no need to setup the trims on the radio: always nice. Something obvious as soon as you start it: the gear ratio is too short and the buggy deserves a longer one to get more top speed. For the rest, the handling is very clean, eventually dull because there is not even the slightest surprise driving it. The chassis sits down very often even if you don't jump it because the suspension is very soft (which is nice at the front, less at the rear).

It seems obvious that this chassis is designed to make no surprise and it can handle motors way more mean than the stock Mabuchi. Overall, it seems very solid and the body molds the chassis close to the perfection avoiding projections onto the electronics. The photos below show how useful it is...

Now I have to disassemble it to ball race it, change the dampers for hydraulic ones and run it again to confirm the changes. I will also change the motor pinion to get more top speed. Depending on the results, I may try to give it a much better motor (and change the TEU-101BK as it can't get lower than 23 turns).

Update 04/08/11: since the publication of this article, my Sand Viper had several runs even if it is not the model I prefer to drive.

From its original condition, I made a few changes, the first one being to install a SuperStock BZ motor. The very dry and low grip track where I run it turned it into a missile out of control. Even if the rear wheels could transfer most of the power to the ground (as long as the spikes resisted), the front wheels were useless. To solve this, I changed the tires for those of the Dark Impact, front and rear but this revealed to be no solution. Only one conclusion to this: the SuperStock BZ motor is too powerful for this very low grip track.

So I chose to revert to less power by installing a Sport Tuned motor and to transfer the SuperStock BZ into my Dark Impact. Performances dropped but I recovered the control over my Sand Viper, even if it still oversteers.

The handling is still very good, without any surprise and reliability is there: despite of several severe driving mistakes, my Sand Viper is very reliable, solid and maintenance free. Very similar to my Dark Impact, the pleasure to drive it is in finding good racing lines, brake and throttle points with the final goal of going as fast as possible.

Update 04/11/14: I sold my Sand Viper.

Since the last update, the motor was replaced with a brushless EZ-run 13T combo and new better tires were fitted for racing at the club. Since my driving skills improved, I finally decided to sell the Sand Viper and to replace it with a more sophisticated TRF201.

During its 6 years in my collection, my Sand Viper never suffered any break or the slightest technical problem, despite my driving being sometimes quite brutal. Only victims of my mistakes, the rear wing I had to change due to the death of the stock unit (a wing not being supposed to act as landing gear), and a servo-saver that died after fighting a stupid tree that was crossing the track  

To conclude, the DT-02 chassis is definitely tough, it merely requires maintenance (basically cleaning) and it is very well suited for learning how to drive. As any modern buggy, the DT-02 chassis (and its successor DT-03) is leaves no room for surprise, thus the "dull" word used earlier: it is quite the opposite of the Hornet handling, or other vintage models "with temper", but the level of performance is also very different.