Teeeeejirrrrr

Shown here is the stock, electric-powered version of the Tamiya TLT-1 truck ‘Rock Buster’.

Construction updates can also be seen here at the full construction thread on scale4x4rc.us.

Overview

This project sort of started by accident. I was bored, waiting for raw materials for something else and decided to use what i had lying around.

What started off as a stock Tamiya Rock Buster TLT-1 1/18th scale electric monster truck is shaping up into an interesting, compact nitro-powered machine.

The engine is from an HPI RS4-2 Nitro 1/10 scale touring car. It has been abused, so it is definitely not in its prime. No matter, as it will work fine for this truck.

This is a picture of it in its current state, along with a cross-section.

So without further ado, here are some answers to some frequently asked questions:

What is this truck unique?
It is a nitromethane burning conversion of what was originally an electric powered truck.
It is also fairly small, as most monster trucks are 1/10 (or close) scale and around 20 inches long. The Super Peanut is around half of that.

What kind of engine is inside it?
The engine is the HPI .15FE, a basic model that came with the HPI RS4-2 Nitro series on-road touring cars. It’s not a particularly high performer, but it has been a reliable little thing so far.

In practice it has shown to be a perfect fit for this truck. It doesn’t have the lightning-quick throttle response of a proper racing engine, and is running with stiff clutch springs, so the truck tends not to wheelie. This makes it a lot more controllable and fun.

How fast does it go?
The truck tops off at around 20MPH or so. I have not accurately measured it yet though. It has an insanely tight turning radius, so it can get very squirrely at high speed. That speed is perfectly reasonable for the truck too, and because of its small size it has the illusion of going very quickly..
Without a radar measurement this guess can be wildly inaccurate. Smaller vehicles typically have the optical illusion of moving faster.

UPDATE! I have measured the top speed of this truck on hard pack dirt with a radar gun- it came out to 21MPH consistently 🙂

Where are the brakes?
The brake disc is hiding right behind the main spur gear. It has been dampened so the truck has a (hopefully) lower chance of flipping over at the slightest touch of the brakes while at speed.

It has four wheel steering?
Yes, in a standard ‘claw’ fashion. One set of wheels turns right, the other turns the opposite direction giving a sharp increase in turning angle and making the turning radius tighter. Of course, when done at high speeds, it makes your model flip over a lot more easily as well.

Is it top-heavy?
It’s actually less top heavy than the stock TLT-1 truck, and definitely less so than variants of the TLT-1 (Such as the Max Climber) that have a new battery clip placing the battery pack high above the chassis. A goofy, non-pickup body was also used to help hide the bulk of the battery pack.

Also, the stock TLT-1 coil-over-oil dampers are pretty much worthless and i won’t be using those on this truck.

In actual driving, the truck tends to do donuts on hard dirt when at mid throttle and the steering is jammed over, instead of just flipping. Not enough time has been spent on pavement, but it would be safe to assume the truck will roll over on that kind of surface very easily.

How about its off-roading performance?
The short wheelbase gives the truck a squirrely ride. Its quite entertaining to watch, and this factor alone limits its top useful speed.
It also has the stock TLT-1 tires, with its goofy super-wide axles, so it won’t have much ground clearance either. This little truck is pretty much at home on large, relatively flat, hard pack dirt surfaces like a baseball diamond infield.

Despite not having much suspension travel (vertical movement is about 3/4″) the truck seems to soak in landings fairly well. However i don’t think any level of suspension travel is going to help with its current short wheelbase setup.

Why run with the short wheelbase?
I went back to the shortened setup to match the ‘box stock’ appearance of the truck, and to also try and keep the it as physically small as possible.

Why the name ‘Super Peanut’?
Tamiya has a glorious tradition of Engrish on their website which manifests itself in very subtle ways. Names of their past kits are just funny without being over the top.

Things such as ‘Terra Conqueror’, ‘Blazing Blazer’, and ‘Mad Fighter’ come to mind. I was just trying to mimic their slick Engrish style 🙂

How’s the driveline holding up?
Unbelievably… very well!

The TLT-1 series of trucks seems to be on the receiving end of quite a bit of harsh criticism from people about its driveline. Some of it has been rightfully so. Before going any further, the one thing that should be noted about these trucks is that very few parts on it are actually ‘new’.

The axles are retooled units that comes from Tamiya’s 1/14 scale big rig lineup of trucks. The transmission is essentially just the belt-driven rear end ripped out of the TA04 series of on-road touring cars.

These are all proven parts with a good track record of reliability. This however does not prevent the kit from looking like it was put designed by a Tamiya intern digging through the parts bin (it really does!). There is one weakness to me in the belt is that it does not have a tensioner and its stock position seems rather slack. At the very least, Tamiya should include an eccentric that makes belt tension adjustable over time. This is where most people are running into their problems, running with modified motors.

The engine in this truck has a slower throttle response, and also has very stiff clutch springs. This in turn gives the truck a nice, soft acceleration which keeps it from tearing the belt to pieces.

How long did it take to build?
Design and construction took about two weeks.
The truck first ran on 16 July 2005.
One of my design goals was to try and fabricate as few parts as possible, using things off the shelf when i could.

So what is the point of this project?
The goal is to create a reliable, fun little truck. I’m not looking for killer performance. I wanted to build something compact that didn’t require a double-wide hand truck to lug around, like my bigger projects ( Mammoet 6WD/6WS, and Tiamat 6WD/6WS ). Those monsters close in at 24 pounds EACH. The Peanut clocks in at just around 3 pounds. It can be tossed into a backpack and run at a moment’s notice.

If i really wanted power, i would have ditched the .15FE and picked up a higher revving engine. The suspension links would also need to be a lot longer to cope with the engine power too.

Why are you using a nitro engine for rock crawling?
Well, this truck was not optimized for rock crawling at all. I built this as a general purpose dirt-bashing truck. The stock TLT in its electric form was not even a very good rock crawler without modifications.

It would perform better with bigger tires and longer suspension links. Why not?
One reason i built this truck was to keep it as small as possible, and that meant using all of the stock driveline where i could. Bigger tires and longer suspension links sort of defeat the purpose of ‘small’ 🙂

Media

I have added a bunch of photos below, during the construction process.

As for videos, they will be added over time as well. It’s difficult for me to get them in during the week since i do most of my bashing on the weekends.

On top of that, this truck is so incredibly fun to drive that i just don’t even bother taking videos most of the time either.

I have a feeling that most of the videos that will populate this section will be made when i’m not actually driving the truck 🙂

	sp_bashing01.wmv (8.3MB) – Filmed 24 Jul 2005. Testing and bashing around in Central Park. My friend John is at the wheel, getting used to the handling (or lack of!) on the truck. This is the second weekend that the truck has been run, and it is happy!
	sp_bashing02.wmv (13MB) – Filmed 30 Jul 2005. More testing and bashing around at Randall’s Island. A variety of people are driving the truck, my friends Chris, Maurice and Ray, who also operated the camera.!

Extra!

Apparently the people at BoyToys Hobby Shop, a Canadian outfit in Toronto are in the process of producing a Nitro TLT-1 conversion kit! I chose a slightly different method of design from theirs but i wish them the best of luck in marketing their rig!

At this time i have no plans for mass production of my system. Check out their media here: http://www.teamboytoys.com/rockbuster/index.htm

Thanks for reading!