xx-4 winter project

[Beau S]

84t spuris the largest you want to go.

Horizon, Losi Parts House, amain, sheldons, etc.. Have random xx4 parts in stock.

Dyno Dan(formerly of TLR), had a new run of belts made ~2-3yrs ago, that horizon use to sell till right before the 22-4 was released. They are very tough to find, I have my own stock pile, & will have the current TLR part header on the pkgs..

They are custom ordered urethane belts... New, super clean & super tough. They ones like you describe have oxidized, & turn to powder while the Kevlar fibers remain. The 22-4 uses nylon faced bando belts that are not the same size as the xx4. The company Tough Belts sells xx4 rubber belts without the Bando Nylon face, so they wear out faster but work to run the car.. Just check them after each race & keep spares on hand.

I may be able to help with some of your Q:'s also..

Use a lil drop of thin CA to fix any stripped plastic holes.

I also highly recommend that you Thin CA in the front chassis inserts. If they wiggle, they will break the chassis. Gen 1 chassis was very thin around theses inserts, Gen 2 almost doubled the plastic around them but would still break if not glued in.

[pumpkinfish]

So far, every front bumper I have found, cracks at the screw holes in the rear and ends up hanging off. I wonder what kind of plastic was used because it feels thinner and "different" than the other plastics. Maybe a 3d printed part could improve the design/materials?

[Coelacanth]

So far, every front bumper I have found, cracks at the screw holes in the rear and ends up hanging off. I wonder what kind of plastic was used because it feels thinner and "different" than the other plastics. Maybe a 3d printed part could improve the design/materials?

Probably the opposite; the plastic used for 3D-printed stuff isn't too durable and mostly only good for shelf or prototype use.

[Mark Westerfield]

The 3d printed plastic on Nix91 stealth buggy has been great during racing.

[Beau S]

It's just a more nylon blend.
The plastic gets brittle as it ages... I would HIGHLY recommend boiling all the plastic parts to rehydrate the plastic. It helps to toughen the plastic back up.

Also, those rear screw holes end up taking a lot of stress. If you use countersink screws there without counter sinking them, it will cause those holes to eventually crack also.

[Coelacanth]

It's just a more nylon blend.
The plastic gets brittle as it ages... I would HIGHLY recommend boiling all the plastic parts to rehydrate the plastic. It helps to toughen the plastic back up.

Also, those rear screw holes end up taking a lot of stress. If you use countersink screws there without counter sinking them, it will cause those holes to eventually crack also.

Boiling ABS plastic will weaken or even melt it. Boiling nylon, however, will do as you said. It's important to mention there's a big difference or someone will risk damaging possibly rare, hard-to-find ABS parts.

[Coelacanth]

The 3d printed plastic on Nix91 stealth buggy has been great during racing.

Which parts, specifically?

EDIT: I just read this:

http://www.rc10talk.com/viewtopic.php?f=35&t=37159

Has this car even been raced yet? The link was only posted a month ago. Perhaps a tad early for durability claims...

[Beau S]

There is NO ABS plastic on this car.. My understanding is that the Front bumper, like most RPM product plastics are high NYLON content products, while the rest of the components are mold blended nylon for rigidity..

Tamiya uses ABS.. and ABS has a very low melting point, whereas the blends used for these cars have around 360-500F melting points.. 212deg F boils water.

I have boiled ALL of all my old xx4's plastic chassis parts.. I bought a lot of old LOSI labeled Spindle and Caster sets, ended up breaking two sets in one race night.. took the rest, boiled them for a couple of hours and let them cool with the water.. I've not broken one since. There is a sponsored guy that used that car to practice with before the 22-4 was released, and he broke one arm, once from an SC hitting him in practice one night. That's the only part he ever broke on it.

If you run it and the car starts easily breaking parts, from minor things.. try it.. Yes, I've even boiled the chassis's

We all tend to dye white car parts by boiling them in the dye... it opens up pores in the plastic and traps the dye.

[RichieRich]

Wow. This is great information. I think the plastics are all in great shape aside from the bumper. I may just grab one from eBay and boil it. Right now, I'm trying to figure out a way to get wheels/tires on it.

I think adding some cvds up front with b44 hexes should allow me to use rulux wheels. I think I need to use the worlds rear hubs to get ruluxs on the back. The non-WE rear hubs have a little notch that pokes up that interferes with the wheel. Or...I could clean up the stock yellow 5 spokes.

[Beau S]

I use to run rulux rims, & just used a washer over the front stub axle threads. It was just a Home Depot bought 1/4in washer that was about 1.5mm thick. The b44 rulux hex is deeper than the standard xx4 fronts. I also started using 22 front wheels after I did my rear 22hex conversion.

I don't think the wheel will rub that nub on the hub, but the worlds hub is basically the same hub with the nub removed. Lol

If you can find the MIP front CVD's, you will also have to replace the front bearings since they are a smaller dia axle. I think it's 3/16's vs 1/4in

[LosiXXkid]

...rub that nub on the hub,...

Fantastic use of words!

[pumpkinfish]

I did boil my bumper before installing. The holes looked like they had stress cracks around them after a few runs then eventually broke. After having a second one fail, I resigned myself to living with it, its not a shelf queen. The front bumpers are kind of rare and can get expensive on ebay. If I ever decide to stop running it, then I'll look for a good front bumper.

One thing I have noticed is this car has so much driveline drag compared to new 4wd buggies. My last race at our indoor clay track it looked like I was putting the brakes on when i just let off the throttle. I'm not sure if I should run the belts on the loose side or not. I'm running the belt tension on "tight" B arrow pointing back. I need this thing to free wheel a little more than it is.

[Beau S]

They do have a natural drag on them, it does take a little adjusting to from Shaft Cars, but the advantage is that you don't have to have drag brake set on your Speedo.

Its not uncommon to run it one step looser than that, but the tension is typically set so the belts wont slip. This is why setting the slipper properly is so critical, and the 22-4 dif & slipper TLR Vids are a perfect way to check your xx4 settings.

The bumpers are a rare item nowadays... I'm working on learning CAD so I get some things setup for 3d print, and that is one of the items on my list..

I've seen some people get 1mm Kydex, and make a sort of front skid plate that's mounted with the rear bumper screws. I have not tried that yet, so I don't know how well it works but seems legit.

I would also double check that ALL of your drive train and wheels bearings are clean and free spinning.. new bearing sets off ebay are sub $15.. and an easy upgrade for questionable bearings.. If one of those bearings start dragging and make the car feel like the brakes are on..

[fredswain]

Several years ago I used to design various drive systems for oil field equipment in applications up to 2200 HP. Chiefly among them were belt and chain drives. I'm actually shocked we don't see chains used in RC anymore. We found that with the oil field equipment that the belt drive system were cheaper and easier to design but the chain drives had less parasitic drag. They of course do have their disadvantages but we found that in terms of mechanical efficiency that a geared drive system, even through a driveshaft, was the most efficient followed by the chains and then the belts. The belts were the easiest to service. The tension needed on belts put more side loading on the input and output shafts and their bearings. Having two belts inline in series didn't double the parasitic losses. It multiplied them!

The chains we did see in RC years ago were severely undersized. That's probably a huge reason that they went away so quickly. They used to stretch early on and you'd remove a link. Then at some point it would break and you'd replace it. A properly designed chain drive (for oilfield use) is one that will need to be replaced once it hits 10% stretch. That's after constant use at rated power for 15 years!!! It should never break! In rc, at least putting a second strand would help immensely. Machining or molding the pullies out of Nylatron NSM would eliminate any lubrication requirements.

[Beau S]

I think the main stay of belts is due to the micro machine industry and the need for quiet running consumer & industrial products. So the belts of any & every size is readily available. Whereas micro chains are not such a standardized and ubiquitously available item. It would be a proprietary product of the RC Company want to produce the car.
And material costs maybe a factor also... I'm just guessing.

I do remember the Ayk Raident, the electric chain saw sound as it raced around the track, & how the chain was cheap bendable links. It would be very interesting to see a 2015 build of a rc buggy chain drive. Hmm..

However, the xxx4 was able to match the freewheeling action of any shaft-drive.. And I never cared for the xxx4 but many did like its "instant on" acceleration, while the xx4 has a smoother on-power response.