Midnight Pumpkin Rear Axle Mount Stripped Screw Hole

[ChaoL]

Hi All,

I upgraded my plastic bushings to rubber sealed bearing this afternoon. During the dissembling of gearbox I found the thread of the screw holding the rear axle mount was stripped both side. I searched a little bit and found solutions like CA glue or even changing the whole plastic part. Eventually I chose the brutal way which is using the epoxy to bond the mount to the rear gearbox permanently! Will change the whole gearbox case and mounts together if needed in the future.

I would like to ask some experience from you experts how to deal with the stripped thread. Are there plastic to metal thread lock?

[picture: epoxy is curing:)]

[MadInventor]

In this particular instance I might have been tempted to put a longer screw in to see if there was more unstrapped plastic to grip the thread. Another alternative would be to use a longer screw and put a nut on the end of it inside the gearbox, but I don't know if this would foul on the diff gear inside or not.

If you are going to replace the gearbox casing eventually, I would recommend using a M3x0.5 tap to cut a thread in the plastic before fitting the bolt. It is not as strong as letting the bolt cut it's own thread, but you can easily feel when the bolt is getting tight, which reduces the chances of stripping the thread and reduces greatly the chances of the plastic splitting.

[Ozzycat04]

I often just put a bit of string in the hole and then tighten the screw ,holds fine for me.

Easy to replace when time to dismantle,no damage either

[ChaoL]

In this particular instance I might have been tempted to put a longer screw in to see if there was more unstrapped plastic to grip the thread. Another alternative would be to use a longer screw and put a nut on the end of it inside the gearbox, but I don't know if this would foul on the diff gear inside or not.

If you are going to replace the gearbox casing eventually, I would recommend using a M3x0.5 tap to cut a thread in the plastic before fitting the bolt. It is not as strong as letting the bolt cut it's own thread, but you can easily feel when the bolt is getting tight, which reduces the chances of stripping the thread and reduces greatly the chances of the plastic splitting.

Thanks mate. I think the long screw inside the gearbox will touch the differential gear. But when I change the whole gearbox case I will consider your suggestion of making the thread first then put the screw in. The reason I stripped them is I often over tightened the screw cos they keep becoming loose after running on bumpy roads for a while. I think I also will look for the metal-plastic thread lock to keep it from loosing again and again.

[ChaoL]

I often just put a bit of string in the hole and then tighten the screw ,holds fine for me.

Easy to replace when time to dismantle,no damage either

Yeah, I tried this method on the other less tripped one and it kinda works not bad. Will see how strong it will last. Thanks!

[Darat76]

Another option you have is to replace all the self tapping screws with machined thread hex screws when you put the new one together, you can use a hex driver to get them almost fully in, then switch to a hex key to finish them off.

Machined screws have more bite into the plastic, so should less inclined to get shaken loose, and doing the final tightening with a hex key (allen key) will allow you to feel it getting tight and reduce the chance of over tightening. Just when doing this you have to use good quality driver and key, coz if it slips it'll round out both the screw head and the end of the key.

[danb1974]

mp/lb uses (cheap?) brittle plastic very different from what you get in better chassis (like tb series), will strip easily if you try to tighten screws mine I think has half a dozen of stripped ones, and was not the first and for sure not the most complicated build

[ChaoL]

Another option you have is to replace all the self tapping screws with machined thread hex screws when you put the new one together, you can use a hex driver to get them almost fully in, then switch to a hex key to finish them off.

Machined screws have more bite into the plastic, so should less inclined to get shaken loose, and doing the final tightening with a hex key (allen key) will allow you to feel it getting tight and reduce the chance of over tightening. Just when doing this you have to use good quality driver and key, coz if it slips it'll round out both the screw head and the end of the key.

Thanks for the method mate. When I change the new gearbox case I will definitely use a more advanced way like yours. So far my epoxy method works really not bad. I found the epoxy has formed new thread inside and it also provides some frictions against the screw to keep it from loosing. I ran the MP this afternoon on a very bumpy area (with little stones everywhere) for around 40 minutes and the screw stayed there very well (before I had to tighten both screws after such a bumpy run). Will see how long it will last well. I attached a youtube link introducing how to repair the plastic thread https://www.youtube.com/watch?v=iqRsLGa8w0w. Of course there are more videos about this topic. Those who do not have appropriate tools could consider this way as a quick fix

[ChaoL]

mp/lb uses (cheap?) brittle plastic very different from what you get in better chassis (like tb series), will strip easily if you try to tighten screws mine I think has half a dozen of stripped ones, and was not the first and for sure not the most complicated build

Yes I have to admit the MP/LB chassis has a lot of problems. I think the pleasure of owning these vintage trucks (like the people owing the vintage cars in real world) is spending time on modifying, improving as well as fixing the truck/car with passion and enjoy the time when they are running well. Just my personal point of view

[danb1974]

I would really like to see tamiya fix the most obvious and annoing issues on those 80's re-re-re-re-re chassis (but hey reusing same old molds is cheaper). Yes it's nice to modify (things like fx10 front suspension, 5th shock mod), but bad plastic I don't know how to fix. Same for those pathetic little springs on the rear axle, which are gone after a few runs.

In the real world on real cars they do fix most common design and material faults (again money driven, this time to our advantage, since there is a 2-5 years warranty). On mine I had clutch pack, timing chain and a/c compressor replaced for free under warranty, each of them with different p/n and supposedly improved parts.

By the way, I seem to find the fx10 front suspension kit only in the states, any place where I can get it in Europe (EU to be more precise)? Anything outside EU goes through customs and I have to wait 1hr in line to get it.

[emory70]

I'm currently building my own Lunchbox with a few mods. What really gets me about the chassis is

1. How complicated it is

2. How it looks like a prototype with so many tidbits that don't serve any function

[ChaoL]

I would really like to see tamiya fix the most obvious and annoing issues on those 80's re-re-re-re-re chassis (but hey reusing same old molds is cheaper). Yes it's nice to modify (things like fx10 front suspension, 5th shock mod), but bad plastic I don't know how to fix. Same for those pathetic little springs on the rear axle, which are gone after a few runs.

In the real world on real cars they do fix most common design and material faults (again money driven, this time to our advantage, since there is a 2-5 years warranty). On mine I had clutch pack, timing chain and a/c compressor replaced for free under warranty, each of them with different p/n and supposedly improved parts.

By the way, I seem to find the fx10 front suspension kit only in the states, any place where I can get it in Europe (EU to be more precise)? Anything outside EU goes through customs and I have to wait 1hr in line to get it.

Yes, I was really annoyed by those two miserable springs too. Fitted the 5th shock two weeks after purchase the MP. I have to say its very nice.

I am afraid I can not give you any help on buying the fx10 suspension. The only things I have done to my MP are 5th shock, rubber sealed ball bearing and a sport-tuned RS540. And I do not have any plan to upgrade any other parts unless they are broken!

[ChaoL]

I'm currently building my own Lunchbox with a few mods. What really gets me about the chassis is

1. How complicated it is

2. How it looks like a prototype with so many tidbits that don't serve any function

It is not perfect, but I love this little truck

[Drivetrain]

Hi All,

I upgraded my plastic bushings to rubber sealed bearing this afternoon. During the dissembling of gearbox I found the thread of the screw holding the rear axle mount was stripped both side. I searched a little bit and found solutions like CA glue or even changing the whole plastic part. Eventually I chose the brutal way which is using the epoxy to bond the mount to the rear gearbox permanently! Will change the whole gearbox case and mounts together if needed in the future.

I would like to ask some experience from you experts how to deal with the stripped thread. Are there plastic to metal thread lock?

[picture: epoxy is curing:)]

Lately I've drilled out the hole and filled it with either gflex epoxy straight or with colloidal silica depending on of the part is structural. It seems to give a good mix between strength and a little flex so it doesn't shatter on impact. So far so good.

Edit: I let it cure then drill the proper sized hole back into the piece.

[emory70]

I've fitted mine with a solid link instead of the 5th shock. I'm running Gmade shocks, and they are just too wide ti use as the 5th unit. And I'll not be running mismatched shocks.