T-shot arm splitting

[Saito2 8309]

This has been discussed in other threads, but apparently the newest rereleases of the Thundershot series cars have a tendency to split their control arms (at the inner hinge pin hole) on relatively minor impacts. This allows the the arms to pull free of their hinge pins. Mine didn't even split on  the mold seam so I'm guessing a plastic formulation problem. I've gone with solid upper arms to help support the lowers but that alone might not do it.

Below is a picture showing the gap in the arm's attachment being taken up with brass tube. Normally, I could see this transferring more impact forces into the rearmost mounting tab but perhaps the arm's flexible nature might deter some of that(?) At any rate, would/could this spacer aid in keeping the arms from splitting? With the front attachment point "trapped" between the front mounting tab and the spacer, I could see it taking more of an impact to split it. Then again, that arm might be so flexible, it could squirm out of its position on impact regardless. Any thoughts?

 

[Jonathon Gillham 4708]

I have no idea if this will help, but will be following this thread. I just replaced a front arm on each of the St Dragon and Fire Dragon yesterday (along with fixing the FireDragon steering thanks to Twinfan). A simple fix like above would be ideal, and I'm pretty sure I already have the brass tube

[StueyS 49]

This is clearly an issue, but I doubt it will improve unless an aftermarket option becomes easily available or Tamiya produce an updated part.

[Jonathon Gillham 4708]

58 minutes ago, StueyS said:

This is clearly an issue, but I doubt it will improve unless an aftermarket option becomes easily available or Tamiya produce an updated part.

It seems to only be an issue with the later batch as the previous runs of rere and original cars didn't have the issue. So hopefully Tamiya fix the plastic and produce more like the earlier ones

[Pizza Frog 772]

I like the tube idea

I've got some leftover blue sprue and when I get the time I will do some tests with different glues to check if they will adhere to that type of plastic, I want to see if the lower arms could be strengthened in the area where the holes are, perhaps a washer or something can be added onto it  

[Pizza Frog 772]

My first tests with cement failed, the glue just flakes off after 24 hours, I purchased some 2 part epoxy today however I've been reading about boiling nylon plastic, 

From what I've read, boiling nylon plastic or plastic with a nylon blend for 3 minutes could theoretically increase durability, I'll test some sprue and see what happens to it.  

[bRIBEGuy 3406]

On 1/9/2024 at 5:58 AM, Pizza Frog said:

My first tests with cement failed, the glue just flakes off after 24 hours, I purchased some 2 part epoxy today however I've been reading about boiling nylon plastic, 

From what I've read, boiling nylon plastic or plastic with a nylon blend for 3 minutes could theoretically increase durability, I'll test some sprue and see what happens to it.  

Boiling nylon parts can strengthen them (this was common practice back in the early days with RC10parts and such), as the material is prone to moisture absorption, and in doing so can help to relieve internal stressed created in production.  That being said, I'm pretty sure that Tamiya did not make the blue Thunder Shot parts out of Nylon.  Boiling other types of plastic often just leads to warped/damaged parts and sadness...

Edit: Ignore my momentary lapse of sanity above where I mistakenly claim that nylon is not not nylon.  Whoops! 

[Saito2 8309]

2 hours ago, bRIBEGuy said:

Boiling nylon parts can strengthen them (this was common practice back in the early days with RC10parts and such), as the material is prone to moisture absorption, and in doing so can help to relieve internal stressed created in production.  That being said, I'm pretty sure that Tamiya did not make the blue Thunder Shot parts out of Nylon. 

It was my understanding that nylon, while potentially attracting moisture, can lose or gain it over time depending on environment. Obviously, in a dehumidified environment, this would lead to embrittlement. Boiling (or even soaking, as boiling just speeds up the process) nylon in water can re-hydrate it.

I'm almost 99% certain the blue Thundershot arms are PA or polyamide, i.e. nylon. That piece of sprue @Pizza Frog has pictured might have "PA" imprinted on it somewhere. I'm also pretty sure they take dye, which is usually another giveaway its nylon.

I'm happy to be proven wrong if that's the case as I don't want to spread misinformation for future readers.

2 hours ago, bRIBEGuy said:

Boiling other types of plastic often just leads to warped/damaged parts and sadness...

Quite true although I've found briefly heating things like ABS up, but not over it glass transition temperature, can relieve internal stresses. It won't "heal" internal stress fractures but it does "relax" the molecules. I used the process to remove the whitish stress marks in a grey Super Champ bumper. One has to do it reasonably quickly with care or deformation is the result. Its definitely not  something I would leave soaking, more like quickly swishing through the heated water.

[Pizza Frog 772]

4 hours ago, Saito2 said:

It was my understanding that nylon, while potentially attracting moisture, can lose or gain it over time depending on environment. Obviously, in a dehumidified environment, this would lead to embrittlement. Boiling (or even soaking, as boiling just speeds up the process) nylon in water can re-hydrate it.

I'm almost 99% certain the blue Thundershot arms are PA or polyamide, i.e. nylon. That piece of sprue @Pizza Frog has pictured might have "PA" imprinted on it somewhere. I'm also pretty sure they take dye, which is usually another giveaway its nylon.

I'm happy to be proven wrong if that's the case as I don't want to spread misinformation for future readers.

Quite true although I've found briefly heating things like ABS up, but not over it glass transition temperature, can relieve internal stresses. It won't "heal" internal stress fractures but it does "relax" the molecules. I used the process to remove the whitish stress marks in a grey Super Champ bumper. One has to do it reasonably quickly with care or deformation is the result. Its definitely not  something I would leave soaking, more like quickly swishing through the heated water.

I can confirm that the sprue has got PA imprinted on it.

[bRIBEGuy 3406]

17 hours ago, Saito2 said:

I'm almost 99% certain the blue Thundershot arms are PA or polyamide, i.e. nylon. That piece of sprue @Pizza Frog has pictured might have "PA" imprinted on it somewhere. I'm also pretty sure they take dye, which is usually another giveaway its nylon.

I'm happy to be proven wrong if that's the case as I don't want to spread misinformation for future readers.

Yup, brain fart on my part... @Saito2 is 100% correct here.  The material is Nylon as shown with "PA" stamped on the Thunder Shot (series) parts sprue (2022 rere).

[Pizza Frog 772]

Sorry for the wait,

I can wholeheartedly say that boiling this type of plastic for 3 minutes doesn't do anything bad to it, there is no deformity or fading.   

Comparing it afterwards to some blue sprue from The D parts tree that hasn't been boiled - they are both very flexible and strong and resistant to snapping or breaking when repeatably bent or twisted.....unless there is a crack in the plastic - then the plastic will fairly easily break when twisted whether it's been boiled or not.  

I would have no problem boiling the lower arms of my Fire Dragon, but I would not know if it in itself was a fix for the splitting effect.  

So I wonder if lubrication on sections of those long screws (BB7) would help as it might prevent the arms from forming hairline cracks which might then quickly lead to splitting.   (the plastic seems to be as tough as nails until there's cracks in it)   

None of this explains why the blue plastic arms from the original release and first rere are fine, maybe the recent rere version has slightly more brittle plastic and therefore it is more susceptible to cracking.

I'm going to go ahead and boil my Fire Dragon's lower arms and when I put them back on I will use a small amount of grease or maybe purchase some dry graphite lubrication.  
 

[Pizza Frog 772]

I've boiled 4 lower arms for 3 minutes, they came out fine, maybe it's my imagination but the 3 areas depicted by the arrows are ever so slightly more noticeable than before?   

For the front arms I also used a 2 part epoxy to attach Tamiya 4mm washers, they are holding on very strong, as least for now

The metal pins feel a bit more snug when inserted in the arms with washers probably due to epoxy oozing, however I have already fitted them to the car to test them and they move freely enough and the suspension works as before, the photos show the sway bar already joined back on

The back lower arms have no washers, they have only been boiled so they can be a control to see if boiling helps

[Super ally 439]

I have the 2005 Thundershot that i bought ready built and was going to buy the new re re to build but this has put me off.Are the plastic arms really that weak?

[Saito2 8309]

5 hours ago, Super ally said:

I have the 2005 Thundershot that i bought ready built

The originals and 1st 2005 rereleases didn't have this problem. The poorly molded bevel gears seem to have cropped up in the first Fire Dragon rerelease (2008?), though its arms proved to be ok for me. Its the latest batch of rereleases that appears to be affected. I'm not sure how easily they fail. Mine split after a gentle love tap with a solid object while negotiating a turn. It didn't even affect the buggy's composure and if it hadn't happened right in front of me, I might have missed the moment of contact altogether.  

[Twinfan 2314]

Mine went after a massive whack traveling at speed through a pothole. It hasn't happened again.

I just grabbed a replacement set of arms and will replace as needed.

Mine was a rear arm by the way.

[Andreas W 3016]

As mentioned by others the problem with the arms must be something of the later batches. I got my Thunder Dragon in 2022,  so it must have been produced in either 2021 or 2022. I don't do skate parks,  but it has done lots of cartwheeling, barrel rolls and kissed curbs  in full drift at good Superstock speed in all from summer to winter temps without any damage so far. I have two D parts trees in inventory,  but so far the Thunder Dragon has been bomb proof. 

 

The same goes for my 2020 second hand Terra Scorcher. This is bone stock with screwpins (preheated) and  without pipe sleeves on them BTW. The only things I have broken on it are the uprights and C-hubs. That was my own mistake and was like a head on crash into a curb last winter. Nothing survives that unharmed and I was lucky that the tub didn’t got damaged.

[Twinfan 2314]

Mine is a Fire Dragon and a similar age to your Thunder Dragon.

It may just be a rogue batch of parts randomly thrown into kits...

[Super ally 439]

The new style cva shocks are different on the new re re as well and i have watched reviews on youtube where they show the shocks are too stiff.

[Twinfan 2314]

30 minutes ago, Super ally said:

The new style cva shocks are different on the new re re as well and i have watched reviews on youtube where they show the shocks are too stiff.

It depends which re-res in the series you're talking about. The Saint Dragon and Thundershot have new CVA2s, the Thunder and Fire Dragons have old-style CVAs.

[Super ally 439]

3 minutes ago, Twinfan said:

It depends which re-res in the series you're talking about. The Saint Dragon and Thundershot have new CVA2s, the Thunder and Fire Dragons have old-style CVAs.

Sorry its the new Thundershot re re im talking about i know that the Thunder dragon has the old style.

[bRIBEGuy 3406]

On 1/20/2024 at 8:59 AM, Super ally said:

The new style cva shocks are different on the new re re as well and i have watched reviews on youtube where they show the shocks are too stiff.

Too stiff compared to what?

Any other modern buggy?  Almost certainly,  yes.

The OG Thunder Shot 58067?  Here it's unlikely, as the original used even thicker shock oil (600cst vs 400cst), and more pre-load spacers on the rear.

An out of the box (as per the manual) Thunder Shot stands proud like a scared Halloween cat, not sleek and low like a race buggy...

[Pizza Frog 772]

I bought some new thundershot/dragon arms from a shop in New Zealand and they arrived today

To my surprise they actually seem to be original arms, they must be new/old stock, they are definitely a different mold compared to the rere versions, the sticker looks decades old;
 

I'm tempted to see if they also have any original BB7 pins in stock because I'd like to compare them to the rere pins. 
 

I've had trouble gluing some road tyres that I bought on aliexpress.  I've tried shoe glue and epoxy -  both easily peeled off, and now I've used silicone, but that only holds slightly better.  I think I may just bite the bullet and get some white Vanquish Lightwight wheels and suitable Tamiya tyres.    I used to run the dragon with a spare set of stock wheels and tyres on hard surfaces but I stupidly sold them; 

[Jonathon Gillham 4708]

4 hours ago, Pizza Frog said:

I bought some new thundershot/dragon arms from a shop in New Zealand and they arrived today

To my surprise they actually seem to be original arms, they must be new/old stock, they are definitely a different mold compared to the rere versions, the sticker looks decades old;

Which shop was that? I've bought all mine from rcmart, should have looked closer to home!

[Pizza Frog 772]

56 minutes ago, Jonathon Gillham said:

Which shop was that? I've bought all mine from rcmart, should have looked closer to home!

RCNZ has them

https://www.rcnz.com/categories/car-accessories/tamiya-terra-scorcherfire-dragonthunder-dragon/tamiya-d-parts-thunder-shotthunder-dragonfire-dragonterra-scorcher/

[Jonathon Gillham 4708]

16 hours ago, Pizza Frog said:

RCNZ has them

https://www.rcnz.com/categories/car-accessories/tamiya-terra-scorcherfire-dragonthunder-dragon/tamiya-d-parts-thunder-shotthunder-dragonfire-dragonterra-scorcher/

Thank you, have ordered a couple of sets - hopefully they are the old ones.