Assembly quirks

[Saito2]

When you build enough of them, its more than likely a quirk or two is bound to pop up in your assembly methods. These can almost be a signature of the builder in a way. I could think of several off the top of my head that I habitually do...

Heating screws. If its a screw that goes into ABS or PC plastic, it gets heated first. Beginning with the obvious ones like the screw pins going into Thundershot series arm mounts or the Hotshot series arms themselves, I've constantly seen these cracked in the older buggies I restore. Whether Tamiya mis-sized the hole or there simply wasn't enough material supporting the hole, I don't know but these always crack. As I've mentioned in the past, the impacts in use often just "finish the job", breaking a part that was micro-cracked during assembly. In an effort to reduce breakage down the line, I heat each screw. Its laborious but I've never had a part split/cracked around a screw hole in any of the fresh builds I've done.

Heating parts. Unlike PA/Nylons that can be re-hydrated through boiling in water, ABS/PC is basically water proof/non-absorbent. ABS/PC's issue isn't one of moisture but rather the loss of plasticizers over time or through UV exposure. If I could invent a way to reintroduce plasticizers to existing plastic I'd be a happy camper, but alas, once the plasticizers have left the building, they're gone. I do slowly heat up old plastics in water I'm restoring and then slowly let them cool. This relaxes internal stresses from impacts over the years. It doesn't really fix anything but its a quirk of mine. Its affect is visibly seen when this is done to grey plastics like a Super Champ bumper. The whitish marks showing stress from impacts can be reduced or eliminated by relaxing the plastic with this method.

Grease. I know there are a million post about trick greases and lubes from other sources to try on our RCs. I just stick with the Tamiya stuff. Ceramic for plastic gears, Moly for metal gears and anti-wear if I want tackiness. I just can't to the "one-dot" method of application though and running dry gears on an off-road Tamiya model gives me shivers, lol. Whether it adds some minimal drag or not, I aim for a thin coating across all the teeth. After opening previously assembled gearboxes I've done, I have a 50% success rate, meaning about half have too much grease that is visibly thrown off the gears. Oh well.

Wax. I don't use grease on external parts that are exposed. I do use wax on pivot pins, dogbones ends etc. however. It doesn't seem to attract dirt like a magnet like typical grease does.

Bearings. I try to use shielded bearing on the inside of gearboxes during overhauls since they are out of the dirt and have less drag. The sealed ones go out by the hubs and wheels.

Gearboxes. I am fanatical about free-spinning gearboxes. I disassemble them several times, checking and shimming if need be. I hate binding.

Those are some of mine off the top of my head. How about yours?

[Gebbly]

9 hours ago, Saito2 said:

Heating screws

I've seen several people mention this. Do you hold every screw under a lighter before screwing it in or is it more subtle like placing all the screws in a pot of hot water or something?

[Saito2]

1 hour ago, Gebbly said:

Do you hold every screw under a lighter before screwing it in or is it more subtle like placing all the screws in a pot of hot water or something?

I can not take credit for the idea as it came from a member who is no longer around. IIRC, they would start the screw, stop and touch a soldering iron to the head of it, wait for heat build-up and then send the screw home.

Personally, I light a candle, hold the screw over it with small needle nose pliers (with adequate ventilation) and then insert the screw. The flame seems a bit less intense than the soldering iron and easier to hit the "sweet spot" temp-wise. That sweet spot is where the screw goes in noticeably easier but not so easy it pushes right into the hole without threading. The idea is to relax the plastic while the threads are being formed by the screw, not liquefy it (or even get close to doing so). Properly heated screws go in about as easy as a screw that's been lubed to aid installation. For suspension screw pins, I only directly heat the small threaded section near the end of the screw head.

It's important to note, this is only for the hard shinny black ABS and PC plastics, not PA plastics (nylons) which a duller, softer and more flexible. Hotshot arms are hard ABS/PC while DF01 Manta Ray arms are softer PA plastic and should not be heated.

[No Slack]

This is new to me but it makes sense. Thanks for explaining.

[markbt73]

Huh. I've never heated up screws before; it never felt necessary. Maybe next time I build something fresh, I'll try one or two to see what I think. I never thought of wax as a dry lubricant before (something like ski/surfboard wax I assume), but that's a great idea too. Probably better than just leaving dogbone ends dry, like I ususally do.

My big one that I can't stand is that "squidgy" noise of air trapped in a shock. It's almost impossible to avoid in shocks with no bladders, but I do my best. If I can get those to be quiet until the very top of the stroke, then I'm OK with it. With CVA shocks, I fill and bleed and re-fill until they're silent throughout the stroke.

I also can't stand rattly bodies. I always put something on the posts to hold the body tight against the pins so it doesn't rattle. I used to use those Dan's RC Stuff foam pads, but I've found that a thin slice of silicone tubing works even better. Just thick enough that you have to push down slightly to expose the body pin hole.

For grease, with me, less is more. One dot per mesh, sometimes none at all. If the tube of grease is in the same room as the gearbox while I'm building it, that's the ideal amount as far as I'm concerned. I can't stand the mess if I have to open it up again otherwise, and I've started to dread cracking open the gearbox on used cars, because I just know it's going to be a nightmare. Maybe it comes from my years running pan cars, which obviously you can't lube the gears on; I've just never found it necessary to have the gears swimming in goop. I stick to the bare minimum necessary to overcome friction.

[Kowalski86]

My main "quirk" is using food based grease on most of my self tapper screws, it reduces friction/heat as you turn them in and out, and it's safe for plastic.

I'm also picky about how I build gearboxes, either they're shimmed or I'll add grease/silicone to stiffen up the diffs.

Anything with your typical 4 body post setup gets tape, aluminum tape where wheels rub, foam pads, old o-rings, whatever I have sitting around. Cheap insurance to make body shells last longer.

[MadAnt]

With the self tapper screws that go into plastic on like every Tamiya kit, I try to avoid retapping new threads when putting the screws back in by turning the screw backwards until I feel it fall into the already cut threads(many other people do the same thing), then I send it in. Sometimes I'll just use my fingers to feel the screw go in. I know many people like to use a power screwdriver, I've used them before too, but I never use it for assembly with old or new plastic. I need to feel how each screw goes and then tightened to what I feel is correct. 

For rattling bodies, I too use foam and silicone fuel tubing on the posts. It just works.

 

[Pizza Frog]

I put a tiny amount of ceramic (cere) grease on the tips of tapping screws sometimes because some screws require a lot of force to tap them otherwise.   I hope I'm not destroying the plastic by doing so but Tamiya do instruct to put ceramic grease on certain non-nylon plastic parts in some kits so I'm guessing it's ok.  

I use a small soft brush to apply grease to nylon gears and pinions, I brush it on until the surface is shiny,  the brush creates a thin coating that won't fly off when running.