SVT's TRX4 - A tale of tiny trucking

[svt923]

So now seems as good as time as any to start a good, old-fashioned buy, drive, modify, drive more, break, modify more thread to share whatever knowledge or experience that may be obtained from me playing with a tiny truck.

As with any journey, we start at the beginning.

The day my TRX4 came home, I was so proud.



This seemingly meaningless event holds some particular significance to the TRX4 world as a whole. The shop I got it from actually received 2 trucks that weren't presold, one went to me then I told Mr. New2Rocks there was a 2nd one still available. He bought that 2nd truck which is currently being used to create all sorts of awesome Bowhouse RC parts like the LCG battery tray and servo winch mount. I will take partial internet credit for these being some of the first TRX4 aftermarket parts available.

The truck feels hefty and solid so I tossed it on the scale to see what is weighs in at: 7 lbs 8 oz out of the box.



How does this compare to a SCXII? The TRX4 is a little less than 2 lbs heavier.



The internet may have mentioned once or twice that the body isn't so light, so lets get some bare chassis weights: 5 lbs 10 oz.



Again the SCXII is still lighter but only about 8 oz is from the chassis. The vast majority of that nearly 2 lb difference is from the body.



I also threw on a whole bunch of wheels and tires to see what fits, it felt like my duty to the TRX4 community as a person that owns both the truck and a borderline irresponsible amount of wheels. You can read about wheels at this thread: TRX4 wheel fitment info

I think that covers everything before I drove the truck.

[svt923]

After I finished all that out of the box stuff, it was time for some driving.

I headed to the most convieniently located proving ground I could think of: my front yard. It contains some of the harshest terrain you will encounter in the typical suburban subdivision, things like driveway cracks, poorly cut grass, a curb, and even a medium sized rock. If this doesn't test the capability of the TRX4, then I don't know what terrain within 10 feet of my front door will.

It's basically Moab and the Rubicon Trail rolled into one.



First I drove it up and down the driveway because that is the natural habitat of the 4 door Land Rover. Just like the real thing, it handled backing down the driveway and driving down the road like a champ. Unlike a real Land Rover, none of the electronics stopped working during this time.

As far as actual driving impressions, it is quite fun out of the box. The TRX4 has no lack of wheelspeed in 2nd gear on 3S and it actually handles fairly well when you unlock the diffs. Speed and handling is the name of the game when it comes to crawling so what more do you need? Ok, low speed control is very good in low gear as expected with 60+:1 gear reduction and a brushed motor. The clearance from the portals provide an immediate and dramatic improvement over the typical scale axle.

The big letdown of the truck is the steering servo, it is way underpowered and even slight binds were enough to completely lock up the servo. It will be relegated to the spare electronics bin in the near future.

These things were noticeable in 15 minutes of driving around my front yard but an hour on the trail the next day confirmed those initial impressions. There was some video taken of the stock trail excursion that I'll have to find.

Overall, much good and not much bad. Things will be tweaked, changed, and replaced because, well I don't really know why. It will happen though and I will probably take pictures to prove it.

[durok]

Your posts are like reading Car & Drivers yearly 10 Best issues back when the hilarious but somehow still informative guys were still around. Great stuff, absolutely love them.....

[JatoTheRipper]

Ah the French crawling course - Cul de sac!

That body is a tank. I can't believe it's around 2 pounds!

[svt923]

Originally Posted by durok

Your posts are like reading Car & Drivers yearly 10 Best issues back when the hilarious but somehow still informative guys were still around. Great stuff, absolutely love them.....

Thanks.

The first issue of Tiny Truck & Driver will be out the day after people start buying magazines again.

Originally Posted by JatoTheRipper

Ah the French crawling course - Cul de sac!

That body is a tank. I can't believe it's around 2 pounds!

I'm living the American dream.

One day I'll add a second rock to the course and build a comp crawler.

[svt923]

I promised tweaking and modifying for possibly pointless reasons and I shall deliver. Also, I have completed my mandatory minimum stock driving time so I'm off probation and free to raise hell (insert head banging emoji).

We all love the locking diffs, right? Well, I love them and this is my truck so I win. Both diffs locked or unlocked is easy to figure out but that middle setting of one locked and one unlocked has set off a discussion with all the civility of an Axial quality debate.

-I want to lock the rear and leave the front open!
-You're stupid, lock the front first!
-Well, I have been crawling 1:1 since 1952 and I always lock the rear first!
-Well, I have been crawling 1:1 since 1872 and any real crawler knows to lock the front first!

I say independent diff controls FTW! To help me, I enlisted the help of my hacked Flysky GT3C in all its 8 channel glory. After much configuring, testing, reconfiguring, and more testing, I ended up with this setup:



The obvious partner to an 8 channel radio is an 8 channel receiver. Those are nice and compact, right?



The receiver box had to go because the receiver is the size of the box. Oh well, this receiver has been conformal coated and is as waterproof as the box was anyway. Notice anything missing from the receiver? The case is so big there is enough room to stick the antenna inside the empty space of the receiver case. Having 4 servos plus the ESC produces just a bit of wire. Good thing I have approximately 5,000 zip ties thanks to Xmas gifts from my mother in law for like 5 years in a row. This really raises questions about the overall practicality of practical items in impractical quantities. When I run out of TRX4 stuff to talk about, we can discuss utilitarian philosophical theories.

If you were too excited about philosophy discussions and ran to brush up on your John Stuart Mill (I guarantee this is the only reference to an early 1800s utilitarian philosopher on RCC), then you probably missed the next upgrade in the last picture.

A Castle 2280kv crawler motor replaces the Titan 550 because brushless and about a thousand other reasons you can read about on other sections of this forum. If you want to know why the 2280kv version over another version, then I will oblige. Out of the box with a 3S pack, the truck has lots of torque from a ton of gear reduction while maintaining reasonable wheelspeed in low gear and a giggle-inducing amount of speed in high gear. I didn't really want to change too much from the out of the box feel and the 2280kv motor matches that driving experience pretty closely. There is still 2 usable speeds but what has changed is a drastic decrease in motor temps. A 3 hour run on a 90 degree day left the motor about as warm as 15 minutes on the stock brushed motor. Its a win in my book, which is the only book that matters, so the motor stays.



I did drop down to a 9T pinion and mounted the motor in the B holes on the motor plate instead of the recommended A holes to loosen up the pinion spur mesh a bit. I'm sure there is a joke to be made with mounting and loosening up A holes but I'm not smart enough to make it. Anyone want to get back to philosophy? No? Fine.

A Mamba X was added to run the motor. No BEC, no fan, no problem.



The stock servo is awful so I got rid of it. The Power HD 23kg waterproof servo is an experiment and so far it is holding up. 23kg is about 319 oz of torque but I'm going to say that is a very optimistic rating based on other servos I have used around that torque level. Either way, its a whole lot better than the stock servo. Have I mentioned the stock servo is awful?



A Protek aluminum servo horn has also been added because I hate plastic horns. This one keeps the steering geometry practically unchanged because it is almost identical in size and shape to the stock one. The Protek horn is about 1 mm shorter for those who are concerned with the length of things .

That steering geometry tastes just like stock.



You can get your very own Protek servo horn from Amain as long as you like 25T spline servos and black or blue is your color. Like red servo horns to go with your Hitec servos? Too bad, Protek hates you and your kind.



For those keeping score at home, we are at new steering servo, new receiver, new radio, new ESC, and new motor. I still have the stock shifting servos because I didn't want to go overboard on new electronics. Tune in next time to see if I actually drive the new and improved TRX4!

(If you noticed the tires are covered in dirt then you already know the answer so keep your mouth shut and let me build interest.)

[svt923]

Originally Posted by Kartooo

love your writing style
very entertaining, looking fwd to more in the future

Thanks for that.

Luckily the future is now.

I will share my number #1, absolute best, most important piece of information I can provide about the TRX4. This is actually so important that I forgot to include it in any post so far.

Without further delays:

The exocage bar over the windshield has 4 holes in it, perfect for holding your body clips.



If you take nothing else away from this long winded, questionably informative thread, make use of this tip.

Your welcome world.

[colbynobo]

Yes, I just had to login to say that the content of your posts and your style of writing are very commendable. Heck, now that I see that I no longer have to rest the body clips in the dirt you've saved me some future head aches. Well done, man.

[wrightcs77]

Where did you get the radio system where was already hacked to 8

Sent from my Pixel XL using Tapatalk

[svt923]

Originally Posted by wrightcs77

Where did you get the radio system where was already hacked to 8

Nick from Helios RC did the firmware hack for my radio a long time ago.

There used to be a lot of guys selling the GT3Cs prehacked but I don't know how many still do, I think Overkill RC is still selling them.

[Mountainsofbeer]

I think the independent diff. controls are the biggest win in this thread, even though its alittle advanced for a lot of TRX owners (like me) its cool to know its possible to do.

Once you get some wheel time with the new motor/esc setup I'd be really interested to know your opinion on it and I'm sure a lot of people will be looking for a brushless upgrade when their Titan motor finally goes or the esc as uncommon as that seems to be. Do you loose cruise control? I almost depend on cruise control when I'm trailing sometimes I have to trail like half a mile or more before I come across anything I want to film or obstacles that require locking the diffs etc. so I just walk behind my truck on cruise control and watch it go Funny to be needing a feature that never existed really before lol

Also forgot to mention the wheel setup it looks too shiny and metal to be stock

[svt923]

Originally Posted by Mountainsofbeer

Once you get some wheel time with the new motor/esc setup I'd be really interested to know your opinion on it and I'm sure a lot of people will be looking for a brushless upgrade when their Titan motor finally goes or the esc as uncommon as that seems to be.

I will definitely be providing some thoughts on the Castle system as I get more driving in but, between you, me, and the 10s of people reading this, it is way better than not bad.

Originally Posted by Mountainsofbeer

Do you loose cruise control?

Of course not

Originally Posted by Mountainsofbeer

Also forgot to mention the wheel setup it looks too shiny and metal to be stock

You weren't supposed to notice those but now that you ruined my totally secret performance advantage, I guess I'll have to spill the beans.

Or will I?

[new2rocks]

I think you need taller jack stands (1:1 maybe?) to lift up the portals what with all that ground clearance. :-P

[svt923]

Originally Posted by new2rocks

I think you need taller jack stands (1:1 maybe?) to lift up the portals what with all that ground clearance. :-P

Better?

[svt923]

So I guess I have to start this post out with a confession (since someone totally narced on me).

My wheels and tires are not stock. Enjoy this picture while the shock sinks in:



Multiple people have tried to convince me the stock tires are legitimately good tires since they are soft, relatively sticky, fairly aggressively treaded, and the foams are close to being good. I remain defiant in saying they are good RTR tires and nothing more. The more I drove with them, the more I felt they slid off lines and hopped while looking for traction on climbs. So, yes they are probably the best tires you can get on a RTR truck (for reasons previously presented to me) but I don't see people actively choosing to run these over other established tires.

In addition to my well reasoned points above, who wants to run stock tires? Lame. Enter the Proline BFG Krawlers with Proline 2 stage foams. They look good and, in the words of Kyle from UCFab, provide all the traction of Hyraxs (Hyraxes? Hyraxen? Hyraxi? I'll Google it later) in a licensed tire. It is everything I could have ever wanted. Proline's 2 stage foams are my new favorite for Proline tires: the fit, sidewall support, and tread compliance are all perfect on the Krawlers. Who knew a company that has been making RC tires for 30+ years could make a foam that works so well with their own tires?



Stock wheels are also lame. Gear Head wheels are not lame, they are shiny and wonderful. These 12 pack EZ locks were the result of receiving some money for Father's Day and RPP having a Father's Day sale at the same time. Like the scale lugs? They are Locked Up M2 acorn nuts and M2x10 set screws since the Gear Head wheels are too thick to use the standard Locked Up M2 wheel studs. SSD hubs are also a recent addition but they will be staying.



Confession #2: I didn't buy pre-dirtied tires, I drove my TRX4.

Let me set scene: it was early Sunday summer morning but you could tell the day was going to be a hot one (since they all are in North Carolina). Two intrepid explorers set off into the empty woods lining the Haw River in search of tiny truck adventures.

Got it? Moving on.

I brought along my new and improved TRX4 while my fellow explorer brought along his Wraith (mostly because he can't stop breaking his other trucks). I threw in a freshly charged 4000mah 3S pack and we were off.



We trekked through rugged terrain,



over mountains,



forded the rivers and streams,



squeezed through tight spots,



and over some dangerous ones.



We returned to camp 3 hours later; tired, dirty, and hungry. So we ended our journey the way all great adventures should: at Bojangles (look it up if you're not from the south, this post is long enough as it is).

The time of reflection is at hand.

First, the Castle 2280kv motor and Mamba X does every good thing about the stock brushed setup as well or better. Low speed control, drag brake, top end wheelspeed, all just as good as brushed. The big difference is heat or lack there of. In 3 hours of constant running mixing low gear, high gear, crawling, climbing, high speed passes, and general tomfoolery, the motor and ESC were barely above ambient temperature (which was in the 90s by the end). The stock setup would have reached that level in 15-20 minutes. 4 servos didn't even tax the Mamba X's internal BEC. It was a very impressive debut for the new motor and ESC.

Independent diff control is just fantastic, the flexibility it provides adds another level to the driving experience. Unlocking the front as you come off an obstacle so make a tight turn setting up the next line or unlocking the rear to let it slip and prevent a backflip are just some of the benefits I encountered. Besides, this is America! The answer is always everything. When someone asks "chicken or burgers?" we say "YES!" When someone asks "front or rear diff lock controls?", we say "YES!" to that too.

The Proline Krawlers are lovely upgrade. They get traction everywhere; dirt, rocks, mud, wet, dry, sand, gravel, baby oil coated glass (I assume). You get the idea. More importantly, they consistantly hold the line you want to take and exhibit little wheel hop when searching for traction. They look cool too, that is as good as reason as any to change something on a scale truck.

Now for the steering servo. The Power HD 23KG servo is much better than stock so it has that going for it. Otherwise it is loud, whines as it constantly looks for center, and probably has less torque than it is rated for. I was able to completely stall it out on a few occasions that I didn't think would give it so much trouble. At least its not dead so there is that.

The stock suspension is on point for a heavy body rig. A lot of people will run for a bottle of lighter shock oil because they think they should based on their other lexan body trucks. When you have a heavy, top heavy body, controlled suspension movement is what you want, that means heavy dampening to slow the suspension's reaction to the shifting body weight. Traxxas pretty much nailed it out of the box.

Nothing has broke, nothing looks worn, nothing feels loose, the body is still perfectly in tact. All in all, life is good. There is now nothing this truck needs. Good thing that has never stopped me before.

[svt923]

Boom! Two updates in one day.

Suck on that Friday productivity.

This update is in honor of a box that arrived.



Anyone want to play "guess what's in the box?"



If you said.....



Paper and air pillows then you win!

If you said....



A Bowhouse servo winch mount then you also win!

That's right, my TRX4 is getting a servo winch. Soon it will possess the power to climb everything! Nothing will be able to stop me!



The Bowhouse servo winch mount allows for you (or your hired help, minions, servants, unpaid child labor, etc.) to install either a external spool or internal spool servo winch in a laid down position for low CG. I just so happened to have this Tower Pro MG958 servo winch with a Locked Up winch spool, Heyok controller, and about 8 feet of 250 lb Spectra line laying around for an occasion such as this. This servo is rated for about 277 oz of torque so I'll conservatively estimate it will lift 15 lbs so dead lifting the TRX4 should be no problem. Lets get installing.

Front bumper and mount comes off



Winch, mount, and bumper all go back on




A hole was drilled in the fake winch for the line to pass through.



I had to trim a bit of my inner fender out to fit my winch. Not a big deal since the servo case essentially plugs up the hole I cut.



This only occurs with the external spool winches but Nick from Bowhouse was not happy and has set off to tweak the design to allow both styles of servo winches to fit with no mods. Knowing Nick, this will probably be done in like 4 minutes.

Added a Hot Racing hook from my favorite parts source: the gigantic pile of junk in my garage. Ready to take on the world.



How does it work you ask. Well the winch barely slowed down doing this:



I will call it a success and I promise to only use this great power for amusement or personal gain. Those are noble causes, right? Whatever, my truck basically has the power of Spiderman now. Later losers!

[calcagno45]

Happy Friday to you and your glorious post.

[Peaker]

That hole in the fake plastic winch, you might want to line that with a brass tube, at least i would.

[svt923]

Originally Posted by Peaker

That hole in the fake plastic winch, you might want to line that with a brass tube, at least i would.

The edges of the plastic have been sanded down and rounded off. I doubt they are any more abrasive to the winch line than the edges of a brass tube.

[HumboldtEF]

Awesome build. Quick question, do those style of winches have issues with getting tangled on the spool. I'm just curious since its enclosed inside the body and must be hard to baby sit.

I just picked up the BowHouse battery box and rear crossmember, its my first experience with 3D parts and I'm pretty impressed.