Brushless Thunder Tiger ST-1

[cart213]

Here is my new project now that I have sold my MT2. I’ve been itching to do something 1/8 scale, since my only experience with r/c so far has been 1/10 scale (MT2 and Stampede). I debated converting a monster truck or truggy. I like the ground clearance of a monster truck but wanted something lighter and with better handling. A truggy is the clear alternative, and I can always help the ground clearance issue by increasing the droop or putting on bigger tires. And if I go racing, then it’s easy to lower it again.

If I was doing a monster truck, I would have gone with the MGT due to the easy layout for a conversion and the durable reputation of the truck. However, once I finally decided to convert a truggy instead, I zeroed in on the Thunder Tiger ST-1. My second choice was the Jammin’ CRT RTR, but I picked the ST-1 for several reasons. It has a reputation for extreme durability and shouldn’t need any hop-ups to handle extreme brushless power. It also has a lower diff ratio than the CRT, so the spur gear is smaller, which allows the use of the Kyosho plastic spur. It also has mud guards, which allows more room on the chassis for electric stuff. It also includes center cvd’s and metal chassis braces, which the CRT does not. Finally, I’ve seen several CRT conversions around here, but I’m not aware of anybody who’s converted an ST-1 yet.

I took several pictures of the ST-1 next to my MT2 to show the difference in size. The ST-1 is MUCH bigger, but I expect it to only weigh about 2.5 pounds more than the MT2 when I’m done. The ST-1 should be less than 10 pounds after it is converted.

Here is my planned setup. I haven’t bought anything yet from Mike, so I’m open to alternatives.

Quark 125b controller
Neu 1515/1Y motor
TrueRC 5s2p 8000mah lipo
Mechanical brakes
ubec

I made a proposed layout in the picture below. I’m going to use Associated battery cups for the lipo and a custom aluminum angle mount for the motor. The center diff spur doesn’t allow enough room for the lipos, so I’m going to flip the diff around so that the spur is towards the front of the truck. I’m going to zip tie the Quark to the aluminum servo plate and hope that it helps keep it cool by acting as a mini heat sink. If the Quark still gets too hot, then I may remove the radio box and bolt the Quark directly to the chassis there so that the chassis will act as a big heat sink. I’d prefer to keep the radio box, though, because it helps maintain the weight distribution and will protect the receiver and ubec from the elements.

If anybody has a suggestion, feel free to chime in.

[coolhandcountry]

Should be a pretty fly set up when done.

[MetalMan]

You might want to ditch the receiver boxes and mechanical brakes. A 5s2p pack would be 54mm (2 1/8") tall, and would be better off split up, with a 2s2p on the motor side and a 3s2p on the right side (IMO).
If you do go with 5s, you might want a slower motor, with a kv around 1800-2000. There is the Neu 1515/2.5D, which has a kv of 1700.

[Serum]

Yeah, ditch the mechanical brakes, you don't need them.

Cool project!

very cool, i was thinking of converting one of these, but i am converting a lightning stadium pro....and on one last note i hope you didn't pay the $700 something for this TT just lowered the price about 2 weeks ago to 430....

[cart213]

Leroy, thanks for the compliment. Your brushless MGT is what made me consider that truck as an option.

I want to keep the mechanical brakes to reduce the stress on the controller and maintain front/rear brake adjustability. I might buy a 2s and 3s lipo and stack them, though. Then I would have the option of removing the radio box and servo and splitting up the packs later on if I choose.

As for the motor, I agree that 2200kv is a bit much, but I don't want to drop to 1700 either. Should I use a 40,000rpm motor or a 31,000rpm motor? Hmmm...

No, I didn't pay $700 for it.

[glassdoctor]

I just picked up a preowned ;) Jammin truggy yesterday, and that's the same basic layout I am doing... except the brake.

Flipping the center diff leaves a nice space for the maxamps packs.... not tons of extra room, but enough to work just fine. I'm going to do a velcro or solid strap setup instead of ass. cups. :) will that get ****?

I have a Neu 1512 for my buggy, and I think I will give it a shot in the truggy too. It's 1900kv, so it might do ok. I'm thinking the 1515 2.5D would be a really nice truggy motor too...

One thing I plan to do is changout the diff/diff gear for a smaller on like the Kyosho plastic 46 tooth setup, and maybe drop to an even lower kv motor.

[cart213]

I finally made some progress on my truggy. I got the motor mount finished and installed last night. I debated with myself for a long time about the best layout, and I finally decided to scrap the mechanical brakes. They were just taking up too much room. Plus, I decided to mount the motor over the differential, and the brakes were in the way. The reason I put the motor on top was so there would be room to mount the Quark directly to the chassis to use it as a giant heat sink. Plus, mounting the motor on top will allow additional air flow around it if I cut a hole in the windshield. The mount has four bolts in it. Two bolts secure it to the diff mount using the caliper mounting holes, and two more bolts secure it to the chassis from underneath. The Quark and the batteries are currently just sitting loose on the chassis in the second picture. The batteries will be held down by Gorilla straps, and the Quark will be bolted to the chassis with an aluminum plate. I should have the truck ready to go sometime this week.

[coolhandcountry]

It is looking closer to run now. You going to test the motor out on it first to see how it works. Then you can determine to go up or down on kv as well.

[MetalMan]

Looks like it's getting there! Good job on the motor mount. 4 screws should be plenty to keep it from shifting. I have one question, though - are the wires on the Neu motor stiff and/or easily bendable?

[Serum]

They look stiff to me.

nice job!!

[cart213]

The wires are stiff like the ones on Feigao motors. I got the batteries mounted last night. Today I'll solder everything up, and then it's go time! I've decided to just use double-sided tape on the Quark at first to see how much it heats up without any heat sinking. If it gets too hot, then I'll bolt it directly to the chassis.

The cool thing about the batteries is that I'll be able to adjust the voltage to run anywhere between 26,000 and 43,000 rpm. Hopefully, I'll never need to swap out my 16t pinion to adjust speed. I can just press a few buttons to adjust my speed from 40 mph up to 65 mph, according to the speed calculator. I've also got a 12t pinion that will provide a speed range of 30~50 mph.

[Serum]

Why would you use that 'boost' thingies? you can also set the epa on your transmitter?

[cart213]

The booster raises the voltage in 4 steps from the natural 13.2V of the batteries up to 21.6V. The runtime loss from the voltage boost is said to be only 5~10%. The transmitter epa would not have the same effect on vehicle speed. It's like having 4s, 5s, and 6s batteries all in one.

[glassdoctor]

As long as you realise there is no free lunch. The price for the voltage boost is less runtime (2x the voltage means 1/2 the runtime) PLUS the 10% loss in efficiency from the device. And the battery will see more current drain... maybe it can handle it ok. THey are pretty good batteries.

A much better solution IMO is to use more cells to get the voltage you want... you get full runtime and no losses.