Brushless Thunder Tiger ST-1
 

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.

http://i25.photobucket.com/albums/c9...st-1layout.jpg

http://i25.photobucket.com/albums/c9...3/DSCF0374.jpg

http://i25.photobucket.com/albums/c9...3/DSCF0378.jpg

http://i25.photobucket.com/albums/c9...3/DSCF0377.jpg

Should be a pretty fly set up when done.

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.

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....

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.

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.

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.

http://i25.photobucket.com/albums/c9...3/DSCF0412.jpg

http://i25.photobucket.com/albums/c9...3/DSCF0414.jpg

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.

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?

They look stiff to me.

nice job!!

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.

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

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.

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.

I personally don't believe in them.

The power that is available from the batteries is not increased. It might work, in an ideal world. (where the current limit of the batteries is not the limit of the setup)

and they can't handle unlimited power either, right?

They are rated at 30C cont. and 60C burst, which would be 138 amps and 276 amps. I'll find out their capabilities soon enough, I guess.

Anyway, I just wired up my speed controller, and I want to make sure that it is ok. Since it will always be used with two packs, I wired up two dean's connectors to it. This will work, right?

http://i25.photobucket.com/albums/c9...3/DSC02931.jpg

That connector arrangment should work just be careful after you connect one pack your other male plug can arc on the chassis, not really a big deal in that brief moment until you connect the other pack.

I don't think that 2x the voltage means 1/2 the runtime. The runtime would be halved only if the current doubled. As long as the current draw remains the same, then a voltage increase will not decrease the runtime.

You have it wired good, butthe series lead seems short. i like to have mine a tad longer to leave room to spread apart a tad to get to the batts. But that's in a maxx.

It's just barely long enough. I didn't want it to have any slack, since it passes directly over the driveshaft.

Then you'll be fine! You may want to protect it in case the shaft breaks. i had a shaft break once and flapped around and wrecked my upper plate before....not good! don't even want to know what would happen if it cuts a wire!!!!!!!

I did my first test run today. I used the A123 packs without the turbos to get a baseline speed. Geared 46/16, the truck got up to 38 mph by my gps. That's almost exactly the 40 mph predicted by Brian's speed calculator, assuming 0.5 in. radius of tire ballooning. With the turbos on full boost, I should be around 60 mph. It looks like I'll have enough speed without the turbos for racing, though. I'll just use the turbos for bashing.

The truck is a mess of wires right now, but I'll post pictures when I get it cleaned up some.

Test it with turbos and see if it really runs 60 mph. I have doubts.

Yeah dude... test them things... I'd really like to see it for myself.... I don't have any confident on those things.... I beleive what gassdr sad.... "no free lunch" but try them on dude.. and Prove us all wrong.. :) great job on the conversion..

and make a vid too lol.. nice conversion btw

Hey cart, I'm reading about those batteries, and they're only capable of 69Amps continuous.... for the 2300mAh packs and the 4600mAh pack.. unless they have a major typo on their website... those battery looks pretty cool... especially the shape of them... and safety.. and charging rate... :)

No, all of the packs are capable for 30C cont. amps, so the 4600 would be double the 2300.

I weighed the truggy and got some pictures of it. I weighs 9.6 lb fully loaded. That's about 0.5 lb heavier than the nitro version. I'll try out the turbos this weekend to see how they do.

http://i25.photobucket.com/albums/c9...3/DSC02938.jpg

http://i25.photobucket.com/albums/c9...3/DSC02939.jpg

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How is the lvc going to work for the turbos?

According to A123, a LVC isn't really necessary...

Your setup looks pretty good! May I suggest that you use some velcro elsewhere besides the battery straps to help hold the batteries in? If the mud guards flex, it could allow the battery(s) to eject.

MM: I can see I'm going to have a similar problem with my buggy. I know I'll need the space over the mudguards and too think they are too liable to break under the weight. I was thinking of making a seperate battery platform (CF maybe?) that would be mounted to the metal chassis with 3/16-1/4" spacers. That should allow the batts to clear the nibs (where the guards are screwed to the chassis) and to keep the weight off the plastic guards.

CHC: Squee is right. The lvc is not needed for these batteries. I'm using NiMh mode on the quark.

MM: It hard to see in the pics, but the left battery is completely on the metal chassis. It's using the middle mud guard mounting hole for the front battery mount. The right battery is mounted to the mud guard at the front only. The mounting hole is only about 1/2" off of the chassis, so the guard does not have much room to flex between the hole and the chassis. About 3/4 of the battery is sitting on the chassis, not the guard, so it should be pretty sturdy. And, I've got velcro under the batteries as well. I will keep an eye on the right side battery, though. Thanks for the advice.

Unfortunately, I won't be able to test the turbos until tomorrow. I used up the batteries and left the charger at work.

Btw, I ran the truck for about half of the pack with the quark mounted on double-sided tape and for the second half of the pack with the quark mounted directly to the chassis. It was noticeably cooler mounted to the chassis, so hopefully the chassis will make a good heatsink.

I got an update and a video for y'all. It is a quick one-handed video with no editing, so sorry for the bad quality. It will give you an idea of how the ST-1 runs, though. I was using the A123 packs without the turbo boosts. The center diff is filled with 50K oil, and the front and rear still have factory grease in them.

Click here to watch st-1

As for the turbo boost, y'all may have been right about them. With the turbos on full boost, the truck was only 5 mph faster than without the turbos installed. Plus, they got really hot after only a few high speed runs. I may have got a bum set, though. I'll contact A123 Racing to see what they say. Even without the turbos, though, the packs alone work great.

After about 15~20 minutes of running, the quark and batteries were warm, but the neu was too hot to hold my finger on it. I'm not sure why, though. Any thoughts from y'all? The gearing was 46/16.

I also noticed a weird quirk with the quark. Sometimes after a full throttle run, I would loose throttle control until I tapped on the brakes. I don't think it was thermalling, because it never felt hot.

Easy on the throttle might help the neu to get a bit cooler, you allmost drive digital. LOL (no offense, i know it's nice to see the truck being launched to warp speed from 0)


Ditch the turbo boosts. i am not surprised they get hot, afterall, they need to boost up the voltage, and this can't be done at 100 percent efficiency.

It does that some times when you loose power for a split second. You have to bump reverse or brake to get it to go again.

that's odd? does it happen after a speedrun or something?

So far, it only happens after a speed run.

Serum, my throttle finger isn't usually digital. I was just trying to show the power on the video. However, it was digital for most of today. I'm still excited about my new toy! :D Maybe the neu will be cooler once I start easing into the throttle instead of nailing it every time! Power sliding on asphalt is too much fun!

You don't know how hot it is now. 50+ degrees start to feel burning on you hands already.