questions for a txt-1 rebuild

[isomer1 175]

I know a bunch of good TXT posts have popped up recently from @Mad Ax, @BloodClod, and @Bertros, but I didn't want to sidetrack those threads with these questions.

Now I hadn't actually planned to own a TXT-1. This past year I got back into the hobby and kinda half-figured eventually I might end up with an Agrios and do the big wheel swap etc. But @Evoman's showroom popped up in a search leading me to keep an eye out on eBay. By some random chance, shortly thereafter a TXT-1 in good condition turned up with a totally reasonable buy-it-now price. Just over a week later it's on my doorstep.

She's in a pretty good shape outside of the expected scrapes on the undercarriage. Appears to be a near stock build with bushings and original can motors. Came with a TEU-106BK ESC and a generic servo on the front steering. From the tape residue on the plates I believe that ESC is an upgrade from the original mechanical speed control. Before starting a rebuild I popped in a FlySky receiver and took it out for a drive around the yard. Which brings me to my first question:

1) It's crazy loud. Like screaming child loud. No way I can drive this around the neighborhood on a regular basis, especially with everybody working from home. I don't want to be that guy. (We already have a dude that drives his 4-wheeler around his backyard in small circles for *hours* , can't be that dude.). From reading forum posts it sounds like these Juggernaut/TXT/etc gearboxes are just noisy in general, but I wondered if anyone had tips to quiet that down. I'm planning on:

• Single brushless motor in place of the twin brushed setup. The motor I have on hand is a Tekin 412, enclosed for water-resistance so I'm hoping that may cut down on the noise a bit.
• Full ball bearings (rubber shielded)
• Non-Tamiya ESC - hoping this will reduce the whine at low speeds.
• Check pinion mesh - have not procured a replacement pinion yet.

2) Suspension. The previous owner has the right, rear cantilever arm set about 1cm longer than the left. I believe this is to add pre-load to offset the torque-twist. For general bashing about the yard, does it make more sense to convert it over to standard upright shocks? I was toying with the idea of cantilevered up-front for more articulation on approach and upright in the rear to resist twist. Any thoughts on that or other setups?

3) Steering. I wonder if this was fairly disappointing build for the previous owner. The steering is very mushy. The servo saver is quite soft, absorbing all of the turn when the vehicle is at rest. Combine that with only front steering and the vehicle takes a lot of back-and-forth driving for tight turns.

• Any suggestions on how strong the servos need to be to turn these Clod-sized wheels at rest?
• Is a servo saver practical on these sized trucks? Is there a better option than the supplied kit version?

4) Wheels & Tires. The kit wheels are in decent shape, just a small chip on one rim that doesn't appear to compromise the wheel. I didn't realize how hard it would be to find spare TXT-1 wheels.

• My understanding is that Clod wheels fit, but that they're more fragile. Is this accurate?
• Are the proline tribute wheels a decent alternative? any others stand out as superior?

Of all of the above, it's really the noise issue that has me most worried. I don't expect a silent belt-drive etc, but I've got to get it damped a bit if it's going to be a regular runner.

Thanks for reading and in advance for any suggestions. Here she is with wheels remounted (please excuse the "covid19-spare-bedroom-buildspace" in the background)

 

[Juggular 4964]

[1]  It shouldn't be that loud.  I've got the older version: Juggernaut 2 which is quite similar to TXT-1.  It's not louder than any other RC car.  If anything, I think it's quieter because gear reduction is made at the center, and when the drive shaft reaches the axles, it's slower.  a) I wonder if the two motors are meshed well? b) I wonder if bushings wore the grease out, and making noises?  c) if one of the pinion's worm gear is loose, it could make noises.  d) it could be universals that's making noises? if so, a drop of oil should take care of it. 

[2]  Stock setting should be fine.  You can start from there, and adjust as you like.  

[3]  This is the strongest servo I have. I haven't installed it yet. I plan to use it without servo saver because I don't like the mushy steering either.  It should be strong enough. But if the servo breaks, it's cheap enough I can buy another one.  If you want more, there are 25kg version too.

https://smile.amazon.com/gp/product/B076CNKQX4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 

 

[Mad Ax 9325]

I would echo what @Juggular said.  I don't recall mine being particularly noisy.  Check the transmission for wear and mesh, if it's not that then run the truck upside down and see if any one particular area is noisier than the others.  It could even be a worn or damaged motor, they can make a horrible scream if the bearings fail.  You can replace with a single brushless motor that will cut down some noise anyway.

When I first built my TXT, I didn't like the soft suspension.  Even with the stock anti roll bars it wanted to lift a wheel and fall over on acceleration and was useless at climbing because the torque would turn it over at the merest sniff of a rock.  Conventional shocks will give you a more conventional experience but as Jugg says, I would try it in stock trim first.  The cantilever setup has its benefits - you can trim each corner independently to add more preload or add more colars to the shocks.  Ride height is much easier to adjust.  Conventional shocks will reduce your articulation, although depending on how you want to run it, that might give you better performance (even in the crawling world, mahoosive articulation isn't always a good thing).

I run mine with Kimbro servo savers, although it hasn't been run in anger for many years.  Since the rebuild it only got one gentle cruise around the garden.  However, I run my Clod with the rigid alu servo horns supplied in the Amazon servo kit linked above by Jugg.  I have that servo too (or maybe the 25Kg version?  I forget.)  If you have a tough servo you can probably run an alloy horn without breaking it, depending on how hard you'll bash and if you avoid catching those big wheels on fence posts at high speed.  (Note that the soft suspension and big tyres will absorb some steering shock, too).

You really need 4ws to get the truck to turn in tight spaces, but it's best to have a switchable configuration so you can switch to conventional steering at speed, otherwise it'll fall over all the time.  Failing that you could run full time 50% steering on the rear which will give you a compromise between steering lock and stability.

If it were me, I'd drive it as-is for a while and figure out what I want to get from it before making too many changes.

[BloodClod 331]

1) It's crazy loud. 

Aside from what you've mentioned, perhaps you want to check the condition of the pinion gear as well. Stock tamiya pinions can wear our pretty fast and if it's worn out it can get noisy. Other than that, maybe post a vid of the noise you hear so it's easier to troubleshoot what it may be. The truck isn't exactly silent, but I wouldn't have any issue running it on the street at night - it wouldn't wake the neighbours.

 

2) Suspension. 

I haven't had a TXT-1 in a long time but the torque twist was quite evident as far as I remember. Like Mad Ax said, it depends on what you wanna do. Slower speeds over uneven terrain, the softer suspension might be a plus. I do more high speed runs on relatively smoother surfaces so I prefer a stiffer truck without the twist. The surest way is to go to a direct mount. Otherwise, keep the cantilevers but preload the rear side that sits on acceleration was what I recall doing.

 

3) Steering. 

Turning the wheels at rest also depends on the surface IMO. I used what I had lying around which was a Savox 1251... rated at 9kg which I think is less than what some of the others are running. It turns the wheels on flat surfaces fine... and more often than not it is the servo saver which unloads instead. I've found that servo savers are a double-edges sword. Personally I'd like something stronger but haven't found anything that I think I'm happy with. I read that some guys run without... but with these tires it's a risk for sure. As for servo savers, most would recommend the Kimbrough 124... I run hot bodies ones myself. One trick you may want to consider is putting a cable tie around the stock servo saver.

 

4) Wheels & Tires. 

Tribute wheels are nice and the width adjustment is a very helpful feature to have *BUT* I've found that Jconcepts wheels are slightly smaller than stock and feature a smaller bead so they work best with their own tires which is a bit of a bummer. The tires are made of very soft and sticky rubber though, so they definitely perform very well.

 

Hope that helps.

[MadInventor 3884]

I'd echo what others have said, just adding this:

As Mad Ax said, it might be a faulty motor, or just dry bearings in one or both of them. The TXT came out in early 2000s, so the motors might be 15 years or more old, more than enough time for the oil in the motor bearings to dry out. Take out the motors and run them and see if they scream. If they do, some 3 in 1 oil dropped onto them will quiet them down, at least temporarily.As with all transmissions, if you think it's noisy, strip it down and look for problems, because you never know what the previous person has done. It might be that the 2mm allen screws are working their way out of the diff housing and are rubbing inside axles. it always pays to check other peoples work...

Stock pinions are aluminium so throw them away at the first opportunity and get some steel ones.

If you're thinking about going brushless, I put a single 1/8 motor in mine (A 2000KV 4274). This runs really cool thanks to all the torque, and if I want to go insane I can run it on 4S. It also has 5mm motor shaft, so RW steel pinions to use with it are the same width as the spur gear in the TXT gearbox.

Steering - I use a 1/4scale HiTec HS755MG servo, but I think it's way overkill, especially as smaller servos can supply much more torque now than they used to be able to. 

Wheels and Tires - Yeah, if you find anyone selling TXT wheels let me know as well ! Clod wheels will not fit. The drive lugs on the inside of the wheels are a lot smaller and if you want to use clod wheels you need Clod stub axles and drive hubs, which is a downgrade as it narrows the width of the axle. I went the opposite way and put TXT wheels and stub axles on my Clod.

Other stuff: I've replaced the centre drive shafts on my TXT with slightly modified Traxxas revo drive shafts, the standard TXT items are chrome plated brass, and if you glue the wheels on the tires they wear out in no time.