A couple DF01 questions

[Saito2 6686]

I'm pulling a box of DF01 parts back into service for "basher" purposes. I'm going to drag this beater everywhere like my work, rain or shine, etc. Upon tear down, I've noted the legs on the motor mount are cracking (expected) and the 4 screw holes in the lower front gearbox that the lower gearbox/front lower arm mount attaches to are fractured. The plan is to spend as little as possible getting it up and running (reliably) Questions as follows:

1. I have a new-on-sprue plastic motor mount available. Are these doomed to fail regardless of the power level? The plan is to run anything from a silvercan to a Sport Tuned, but nothing more powerful. Should I just get the metal mount and be done with it?  It already has an upgraded prop shaft making the full Tamiya upgrade kit half redundant.

2. Any ideas on preventing the gearbox from fracturing again? Admittedly, it was built long before I started assembling using the "hot screw method" which, so far, has cut down on typical fractures around ABS screw bosses and such. Maybe this would be enough. Another idea would be to tap the holes and run machine screws instead of tapping screws. Thanks.

[TurnipJF 9192]

1. Failure of the plastic mount is inevitable even on a silver can. Best bite the bullet and get a metal one. You can get them on their own - no need to go for the half-redundant upgrade kit.

2. The hot screw method is good, as is drilling out the first millimeter of the screw hole to 3mm, thus ensuring that the screw only starts stressing the plastic after it has been inserted 1mm into the hole. The 1mm of unstressed plastic around the edge of the hole helps prevent, or at least delay cracking of the part.

[Saito2 6686]

Good idea about taking some of the stress off the initial depth of the hole. Perhaps its just my experience but it seems like Tamiyas around the Astute/Madcap era up into the DF01 era are more prone to these fractured plastics. I realize they all did it a some point (i.e. Hot Shot inner screw pins into suspension arms, etc. or simply age/UV exposure) but the cars in the aformentioned time period seem most afflicted. I wonder if Tamiya plastic quality was bad at this time or if they had begun implementing  newer designs that simply over-stressed the material they commonly used up till then.

[WillyChang 1814]

If I have to use the plastic mount on that generation of gearboxes, I swap to machine thread screw... think you can get a slightly longer screw in there, 12mm if not 16mm. Feel for depth of hole.

 

But yeah, alloy mount is better. Cheap aftermarket mount works well enough, don't need the original hopup. If the mount doesn't come with the direction key (mount is not the same if flipped 180deg) compare motor hole locations & work out which way should face Up; then I engrave on it Up on top & an arrow pointing towards front on the bottom side. 

If building a MantaRay I also like an alloy front shock tower. Seem to break a lot of those plastics, and spares only come on a huge whole sprue.

One of the popular budget alloy brands made both items in blue alloy... think it's YeahRacing if not GPM. Cheap & works.