TRX-4 Monster Truck?

[MODC]

That's one of the best posts I have seen...lol

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[indybama]

A box truck monster truck, thats great! Lmbo

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[smog]

[JatoTheRipper]

That is funny!

[TooOldForThis]

In case anyone missed it, the guy over at BigSquid finished his. I think the proportions look really nice with the Ranger tires.

Somehow it seems like the idea of a TRX-4 monster truck went completely mainstream before I could even collect all the parts for mine. I still have a fun idea for a paint theme that should help set it apart. It's hard to be original with a platform this popular!



Monster Truck Madness – High Horse is Alive! « Big Squid RC – RC Car and Truck News, Reviews, Videos, and More!

[JatoTheRipper]

Ranger tires are ugly. I wish JConcepts would release a nice, modern tread 2.2 tire. 2.2 monster truck tires are dying. So snatch them up if you want them. I think the Rangers will be around, but Proline killed off their 2.2 Destroyers and I have no idea why, but I snagged a set before they're gone.

[TooOldForThis]

The tires from the MST MTX-1 aren't bad IMO. Possible alternative to the Ranger tires. Couldn't find confirmation of rim size but they look to be 2.2.

[TooOldForThis]

It's working surprisingly well so far. Everything about the chassis is stock except for the Traxxas lift kit and the Hot Racing +10mm axles on each side. It's in the short 12.3" wheelbase configuration.



Amazingly, on flat ground it doesn't lose any steering angle! At full lock the inside tire just barely brushes against the lower link.



The rear tires only contact the inner fenders in the last 10% of shock travel when flexing, and even then its only minor rubbing at the front of the wheel opening. I think this could be dialed out by limiting shock travel a tiny bit and/or switching to the long 12.7" wheelbase configuration.



The front can flex equally as well when the tires are pointed straight ahead. Predictably, there is severe interference with the inner fenders if you give it much steering at full compression, but it wasn't much of an issue during a quick test drive. The front corner of the fender should be trimmed, but besides that I think the rest could be dialed out by increasing spring preload, limiting shock travel slightly, and reducing the steering angle limit slightly.



Overall I'm calling this a huge win because I really didn't expect to be able to keep the inner fenders.

Now to decide on a body...

[durok]

Who would have thought Traxxas would have released a vehicle that works well with massively upsized tires?

[TooOldForThis]

There has been much tinkering.

I switched the diff lock operation so it starts with both diffs unlocked, then rear locked only, then all locked. I think this will be better for the general bashing type of driving this will see. This was done by switching the diff servo wires at the receiver and then reversing both diff servos via settings in the transmitter. Thank goodness the manual for the transmitter is online because I never would have figured out how to reverse the servos without it.

To address the tire rubbing, I limited the max steering angle (again via transmitter settings), trimmed the front corners of the front fenders, and put fuel tubing on the shock shafts to limit travel. The shocks in the lift kit come with black plastic sleeves on the shafts to limit travel, so all I did was remove and replace with a longer section of fuel tube. I see this as a starting point that will be followed by a test drive and then more fender trimming or more fuel tube as needed. If someone wasn't running inner fenders they wouldn't have to do any of this but I'm determined to keep them. For now anyway.

[TooOldForThis]

So it gets a pretty severe servo shake if you steer it when the tires are off the ground. There is play in the steering and it oscillates back and forth trying to find center, and sometimes it won't stop until you set the tires back on the ground. Has anyone experienced this? I'm thinking it's one of three things:

1. There could be some play between the metal servo horn and the servo (I think the play is actually inside the servo but I haven't checked yet)
2. The servo is defective / out of tolerance
3. The servo normally has some play internally and this is just what happens with really heavy tires.

Either way, not a big deal because I have an aftermarket servo on standby. Oddly enough, after all the bad things I've heard about the stock servo, it actually does an OK job of turning the tires... when it's not shaking itself to pieces trying to find center anyway

Meanwhile, the body decision has been made. I picked this one because it comes with a bunch of nice molded plastic details and I think it will look OK with the extra-large wheel openings that will be needed.

[TooOldForThis]

More fine tuning. The TRX-4 starts out like 90% ready to work with these tires and all you have to do is chase after the details. Under some conditions (like backing up with the diffs locked at full steering lock) the inside front tire could get pushed into the lower link, which would instantly stop the tire. Servo endpoint adjustment wasn't preventing it reliably. My solution was add to the existing physical steering stop with a tiny screw. Looks like that should do the trick. It could be adjusted by adding washers under the screw head.





Edit: also, it appears the steering shake I mentioned in the previous post is due to play inside the servo. I don't know if this is normal or if I got a bad one. Oh well, gonna run it till it quits and then replace it.

[TooOldForThis]

Time for an update. I was having a lot of "fun" with the radio over in this thread which had me thinking about calling the whole thing off but it seems like that should be resolved. Even if it's not, I made too much progress this weekend to walk away from this project now.

So obviously with a monster truck you want to get the body up higher than normal but the limiting factor again turned out to be the inner fenders because the body's wheel openings can't go higher than the top of the inner fenders without looking funny. As a result the body is probably less than an inch higher on the chassis than normal. (Note: I've switched the chassis over to the long 12.7" wheelbase configuration)



This body height doesn't leave much room for the tires to move up and down so you have to work on the wheel openings quite a bit. I used a 6" diameter coffee can to trace out a decent arch, then to smooth it out after cutting I sanded them with sanding paper wrapped around the side of the same coffee can.

Looking more monster-trucky now.



I wasn't planning on using the bumpers from the TRX-4 kit but they actually look pretty good with this body. To get room for the front tires to steer I made the front bumper a "stubby" by trimming off both sides of it.



The back bumper is functional in the sense that it allows you to ride out wheelies without tearing up the back of the body. I've already tested this out and it works great.

[TooOldForThis]

Getting close to finished now. Anyone following this thread probably only cares about TRX-4's or monster trucks but TOO BAD, WE'RE GONNA TALK PAINT

I decided to do the paintjob on the outside and wanted blacked-out windows (sorry not sorry ) so the first step was to paint all of the the inside black. Then I masked the windows off on the outside and went over everything with Tamiya's flat clear, which makes a surface for generic enamel paint to stick to. The front of the body is held on with magnets (a first for me) and you can see them in this pic, already glued under the hood.



Next I went over all of the outside with Rustoleum American Accents metallic aluminum spraypaint, available at Walmart. I've used this paint before with great results, it sticks well and dries really fast. Its good if you want to sand through the topcoat later on to make it look like the paint is wearing off. Not sure if I'll be doing that to this body, but it doesn't hurt to have it under there anyway.



That's all of the paint prep work done for this body, now just have to lay down the top coat. Here's an example from another body I did of the effect you can get by sanding through the topcoat to expose the silver paint.

[JatoTheRipper]

This is going to look incredible!

I like the screw bump stop idea. Nice thinking!

[soze]

TRX4 Monster truck.... hmmmm..... I might need more TRX4s...

Progress is looking great!

[TooOldForThis]

Done! It's a military theme. Sharkmouth stickers from Ebay and some waterslide decals meant for a tank. Decided not to do any wet sanding but that silver paint is still under there, waiting to make future scratches look more realistic .

This project came together surprisingly easy. The biggest frustrations I had were with the stock radio, which had nothing to do with the monster truck conversion. If you're thinking about making your own TRX-4 monster, I have some tips:

1. It's pretty rad, DO IT.
2. Ditch the inner fenders. Almost all of the clearance issues I had to solve were due to those fenders. You'll also be able to mount the body higher without them, and more higher is more better.
3. You might not even need the axle extensions. I didn't try it without them so I don't know.
4. Try a narrower body meant specifically for a monster truck like one of the ones from Jconcepts or Proline. The proportions would look even more monster-trucky.

[mgputer]

Turned out fantastic. Looks like an 80s monster truck. Just awesome.

I was thinking about making an original Bigfoot with a trx4. Definitely gives me some inspiration.

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[MODC]

Originally Posted by TooOldForThis

Done! It's a military theme. Sharkmouth stickers from Ebay and some waterslide decals meant for a tank. Decided not to do any wet sanding but that silver paint is still under there, waiting to make future scratches look more realistic .



This project came together surprisingly easy. The biggest frustrations I had were with the stock radio, which had nothing to do with the monster truck conversion. If you're thinking about making your own TRX-4 monster, I have some tips:



1. It's pretty rad, DO IT.

2. Ditch the inner fenders. Almost all of the clearance issues I had to solve were due to those fenders. You'll also be able to mount the body higher without them, and more higher is more better.

3. You might not even need the axle extensions. I didn't try it without them so I don't know.

4. Try a narrower body meant specifically for a monster truck like one of the ones from Jconcepts or Proline. The proportions would look even more monster-trucky.

That's a fantastic job.
Wonder how the traxxas big foot #1 would look/fit on it.

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[MODC]

Pics....

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