Hotshot II Carbon Chassis Rebuild/Restore

[cambragol 152]

This is my first post here. I have been viewing these forums for a while, enjoying all the posts, especially those that focus on building older Tamiya models. 

I am new to the RC world. During the 80s I was never able to own or build any cars. Just stared at the Grasshopper and the Frog in the local hobby shop. Got to try a Wild Willy once, that my uncle had made. Very sad childhood.

Now a dad, bought a Grasshopper, then a Hornet, for my boy. He built them on his own like a champ. Made me jealous. Bought myself a Boomerang. Very fun. Built it, added lots of...er...hopups?

However, I always thought the Hotshot looked really sweet. Couldn't justify buying one with the misses for sometime. Finally, thanks... to er...the Chinese Pandemic...had more time on my hands and was able to get my hands on this:

I plan to merge the above, with this:

I am a little ways into this build/rebuild, so I will have to do some catching up. I'll document things here for fun. Not sure if anyone is interested, but I at least know that the wifey is not. Perhaps someone here is.

In any case, Greetings!

[cambragol 152]

I heard the 'Builds' likes lots of photos in posts here, so I will try to oblige.

Started taking the Hotshot II apart. It has a few neat aluminum parts from back in the day. I'll try to restore/use those in the end. You can see from the pic below that one of the aluminum upper suspension arms is bent horribly.

Noooo!!! The rear shock tower is toast. Not the easiest piece to resource I think. Hmm.

[cambragol 152]

So many little things to do with this project. Let's start simple. I removed the stickers from the roof, straightened it out, as it was bent in a few places, then polished it with 600, then 1200 grit sandpaper, then used a sanding 'eraser' which is about 3000-6000 'grit', then finished with a polishing cloth. 

The roof is now almost as good as new, and certainly shinier. I also saved all the retro stickers.

[cambragol 152]

Tires. If you noticed in the first post, the Hotshot came with mismatched tires. I got another pair of each (very used) soaked them in glycerin for awhile to soften them up (it really worked!), then gave them a coat with a 'tire blackening' spray I use on my actual cars wheels (which also worked nicely!). They look newish now. Next up was getting those nice white lettering effects.

For this I tried a 'Gundam Marker':

 

The first coat is a little patchy. But, multiple layers can be applied. Holding the brush tip mostly sideways allows the paint to go onto the raised surface of the letters only. Very few spills, and not too hard if you have a steady hand.

 

 

After 2 coats they look pretty even. Smashed the tires around a bunch and have seen no flaking of the 'Gundam Marker' paint yet. Doesn't crack either. Time will tell though...

[cambragol 152]

Did the same with the other set of wheels. Only painting on the raised portions of the lettering is a little more ambitious with the stock Hotshot wheels.

 

Not perfect, but I think I will proceed. I have not seen this take on lettering these wheels yet.

 

Coming along decently. Not perfect, but decent. Again, holding the 'Gundam' marker almost sideways is the trick.

 

Almost done. Switched out the wheels to test the look. 

 

Finished up. This took 1 and a half coats as well. I think one side will do for now. Whew.

[Snappy1 1005]

Some very interesting mod parts already fitted, I think those are see's rims too, very valuable

looking forward to your updates, not many Hotshot II's around.....

[cambragol 152]

I guess that post above showed this:

Picked this up in Japan (where I live). Still lots of old tamiya/rc parts available here, if you scrounge. There is an RCChannel bumper attached to this 'Eagle' bumper as well.

The wheels are not 'actual' Sees' wheels. Replicas I guess, which you can pick up here:

https://www.ebay.com/itm/333432391015

The seller has black and red versions as well, if you ask nicely.

 

I am not sure if this will really be a Hotshot II by the end...lots of the base parts crumbled on me. I plan to take it in some slightly different directions, but will try to keep the Hotshot II vibe, if that is possible.

[cambragol 152]

My next task that I will document is the restoration of the front/upper aluminum suspension arms. They seem rare, and it was nearly impossible to track down any images or record of them anywhere. But I did eventually. Though...I can't remember the make...just that they were sold, in the 80s, maybe just in Japan.

They seem a little weak, and there is evidence to support that based on the condition I found them in. However, it seems the true weak point is the m3 screw rod connection between the arm and the rod end that attaches to the knuckle.

[cambragol 152]

Before I go to far into this, I need to first strip off the gold anodizing. I'm going with red and black in this build. So good bye gold.

I also had some other pieces that needed some color stripping. Namely, this bell/crank by Yeah Racing, though not the turnbuckles. They can stay

 

I also picked up some random pieces that I might be able to use. 50 yen each at Bookoff.

 

Threw these into a glass bowl with, basically 'Draino', though I used a japanese brand. About 5 minutes can strip the color from the anodizing, but keep some of the surface. More than that and you start etching down to raw aluminum. A look I like.

 

Here is the finished look with the Yeah Racing pieces:

 

The Bell crank is going to be mounted like this:

[cambragol 152]

The rod ends of the aluminum arms were a little damaged as well. The thread seems to have become a little loose, such that no matter how tight I crank the rod, it wiggles. I want no slop, so I had to replace them. I tried a couple of different rod ends, but they all had a tiny bit of slop. Unacceptable, so I ordered left-handed joint bearings, and they are as tight and as smooth as can be.

Left-handed, because I am going to use them with some titanium turnbuckles from Tamiya. But the joint bearings are just a tad too long. I show the rejected Yeah Racing rod end candidate as well. The original retro part is on the far right:

 

So I had to ...er... shorten the joint bearing. Started out by sanding one down. Then bought a dremel and got serious.

 

Now I put it all together. Notice the weird little 'bolt' that goes through the eye of the joint bearing. Very weird, and could not find another like it anywhere. So it may be unique to this piece and somewhat irreplaceable. Added some foam to make sure the fit is snug and slop free.

 

Now the pieces are both restored. They are solid, zero slop, probably stronger than they were originally (titanium turnbuckles) and allow for some adjustment to the er...camber of the front wheels. Here they are temporarily placed into my first RC build ever, which was a boomerang, that I mentioned previously.

 

[cambragol 152]

Okay, next up was/is all the holes for the suspension pins. The mounting holes in the gearboxes, on the arms, and on the knuckles are all very loose. LOOOOSE. I even got another wrecked Hotshot (first re-release I believe) for a steal, and added its parts to the mix (no pic of that car before I tore it down. Nothing notable there though, sorry), and they were all pretty loose too. Additionally, some of the suspension arms and knuckles have small cracks. Yikes.

Well, what I did next is probably not the best idea, and I am sure someone with more experience will point this out to me, but I have little to no experience myself, so I just did it. I decided to drill holes in all the pin holes (4mm holes) and re-sheath them with metal!

I went with copper first. Easy to find. I drilled the holes on a drill press (at my local mini4WD shop) to make sure everything was very precise.

Copper sleeves fitted:

Yes, the gearbox is assembled. I have taken it apart and reassemble it two or three times to get all the shims perfect etc. I don't count it as finished though, as I still haven't worked out what I will use for dogbones or universals, and that will impact how I put the gearboxes together, or at least how I make the outdrives line up. The boomerang taught me that there are some issues potentially here with binding. Anyways, later for that.

 

After that I decided to go with steel pipe, rather than copper. The steel pipe I found was a tiny bit tighter than the copper pipe, and hence less sloppy. I tried aluminum pipe too, but it seemed too soft, and not as precise as the steel pipe. Here are some of the arms and knuckles fit with that.

The Hotshot II knuckles are waiting for their steel sleeves in the background. I'm waiting for more steel pipe to arrive. Used 50cm of it already!

 

Here are both the Hotshot II and the New gearbox fit with steel sleeves:

 

Well there you go. Probably a bad idea (and already was, as I ruined one entire gearbox when drilling and had to order a new one.) but it is done. At least the suspension will have zero slop. Is it stronger? Hmmm...time will tell. Likely no.

[Snappy1 1005]

Your sleeves look great, if you ditch the stock screw pins in favour of some steel shafts with C/E clips it would be stronger, well less likely to crack arms .

[cambragol 152]

1 hour ago, Snappy1 said:

Your sleeves look great, if you ditch the stock screw pins in favour of some steel shafts with C/E clips it would be stronger, well less likely to crack arms .

Thanks! And definitely, steel shafts are in the plan. Unfortunately these arms are all the originals and the stock pins had been used, so there were already some small cracks. The drill hole hid most of those.

 

I forgot to mention above that I used Gorilla Glue to anchor those sleeves in place. The drill hole was quite precise, so there was a possibility of the sleeves popping out. The gorilla glue holds them in place real nice. Gorilla glue is a bit rubbery when finished, so I think it will work well to bind the sleeves to the plastic of the gearboxes and arms. Not too brittle, absorbs impact a little, flexes a little etc.

[Cynan 520]

Great work.

Where did you buy the steel pipe from?

[cambragol 152]

3 hours ago, Cynan said:

Great work.

Where did you buy the steel pipe from?

I tried to source locally, and was able to with copper, brass and aluminum. However steel pipe was a no go, and with travel a little bit restricted I resorted to ebay.

I prefer to avoid buying stuff from China, but in this case the only seller I found was from there:

4mm OD x 3mm ID Steel Pipe

This pipe was the tightest I found. Allows smooth rotation, with almost zero wiggle.

[cambragol 152]

So, I am waiting for more metal pipe. Not much I can do right now. Decided I would finish the lettering on my wheels. I know how to do this now, but there was a time I was looking around for tips on how to do it. I will describe my technique here, and try out adding a little video to illustrate.

I use a 'Gundam Marker', which are ubiquitous in hobby shops in Japan, but I am not sure of their availability elsewhere. I am not 100% certain what kind of paint it contains, but in my tests the paint is very flexible, and does not flake easily. So it might even hold up for a bit of action. But this is wholly cosmetic of course.

The marker needs to be fairly dry to start. Too much paint flowing will instantly ruin things.

The main 'trick' for this is to keep the marker tip held mostly horizontal and parallel to the raised surfaces of the letter that you wish to paint. You will be using the side of the tip, not the tip itself.

To do this you should be slightly rotating the angle at which you are holding the tire to match the angle of the side of the pen's tip.

Then use short, very gently strokes to just run the pen tip's side along a section of the raised lettering. 

Next, have extreme patience and do every letter. Haha.

Here is a vid showing this technique:

 

[rwordenjr 1893]

**** I want those black/silver wheels ! Would like mean on mine 

[cambragol 152]

Yes they would. Get them right here: Hotshot Alloy Wheels You just have to ask the seller to exchange gold for black (if he has any left). He is Korean, but he can speak English/use google Translate.

I have those same shocks! (Korean as well) However, I opted for these bad boys instead:

They are for the Traxxas Slash. Very very big bore.

[rwordenjr 1893]

7 hours ago, cambragol said:

Yes they would. Get them right here: Hotshot Alloy Wheels You just have to ask the seller to exchange gold for black (if he has any left). He is Korean, but he can speak English/use google Translate.

I have those same shocks! (Korean as well) However, I opted for these bad boys instead:

They are for the Traxxas Slash. Very very big bore.

Thanks for the tip! The blacks are on the way 😍😍

[cambragol 152]

53 minutes ago, rwordenjr said:

Thanks for the tip! The blacks are on the way 😍😍

Noice! He's a good seller. Bought 6 sets of wheels from him!! They all look great on pretty much any car.

[cambragol 152]

Okay, pipe arrived, and I got back to work on sleeving stuff. I'm using a nice little pipe cutter, which makes cutting the pipe smooth.

However, it leaves a little lip along the end of the pipe.

 

That has to be sanded down, quite laboriously.

 

The tolerance of this pipe is very very low, so each sleeve takes a decent chunk of work.

You can see the original cracks in this picture. I'm not so pleased with that, as obviously sleeving is not really going to fix/strengthen that. There are some plastic/epoxy solutions I could pursue, but the cost of buying that/those, is about the same as buying a new pair of arms, which are still available here and there thanks to the re-re-release of the Hotshot and Supershot. I'll have to think on that. Maybe just use these for now, and when they break, replace with new pieces.

[cambragol 152]

Now I can move on to more exciting stuff. Next up is the rear suspension.

I already put the rear gearbox together. Pretty standard. Added shims here and there to make the new outdrives work with the old Hotshot II gearbox. There were some spacing issues, but it was minor stuff.

I heard that the Hotshot lower rear suspension arms suffer from breaks a lot. So I wanted to get aluminum arms. However, there are none available as far as I can tell. Except RCchannel stuff, but that is for Hotshot, not Hotshot II. I want to keep the shocks forward of the rear suspension arms. I like that look, and it is definitely part of the Hotshot II's look.

So I looked around and found these:

I think they are lower rear suspension arms (aluminum) for the DT-03 or Dt-02. I forget which.

I knew that wouldn't fit, however, their geometry is very close to the Hotshot II lower rear suspension arms. So I took a gamble that I could make something work, and ordered them. 

Here they are after a lot of filing down to make them fit onto the gearbox, and with the red Hotshot knuckles:

 

Lining things up with the various suspension peices from the Hotshot and Hotshot II, I came up with a new geometry that should work very nicely. I get to keep the 'forward' shocks (and use the HUUUGE Traxxas Slash shocks I bought) and keep the general swept forward look of the rear suspension arms. 

Here are some images of my 'plan':

[cambragol 152]

The original shock tower is shot, as can be seen in the first post. So I needed to track down some options.

First I found this on ebay:

I found it from this seller, though currently he is not offering the Hotshot II shock tower.

 

However, I wasn't so sure about the double 'carbon' look (of the tower and the body), additionally, I wanted to do something a little different. I tested out my boomerang tower with the geometry I was working on for the back, and it seemed to work, though would require some imagination/work. Critically, the mount points for the boomerang tower were slightly (maybe 5mm) too narrow, and would cause the shocks to rub/bend the roll cage (or they just would not fit).

Then I found an alternative aluminum boomerang shock tower that would solve this issue. It has two mount points for the shocks, one of which extend the mount point about 5mm out. So I got that too (they came in a set with some front shock mounts, Superhotshot style.)

 

But oh nooeees! Horrible blue anodizing!

I'll take care of that. A little bath in Draino, and some polishing give us raw aluminum beauty:

 

Next up will be putting the rear suspension together with one of these options...

[Cynan 520]

There is a 3D print file available for the HS2 rear tower as another option.

Also, and I suspect you know and/or don’t kind with the other upgrades you’re doing but just in case - the top rear arms are not HS2 specific as those had triangles in to match the bottoms. The circle cut out style arms are from the HS/SHS only.

[cambragol 152]

18 minutes ago, Cynan said:

There is a 3D print file available for the HS2 rear tower as another option.

Also, and I suspect you know and/or don’t kind with the other upgrades you’re doing but just in case - the top rear arms are not HS2 specific as those had triangles in to match the bottoms. The circle cut out style arms are from the HS/SHS only.

Yeah, I have seen that as well. Doesn't look very nice when printed out though, unless you have a really good printer or get it done at shop.

And yes, I know that those arms are for the HS/SHS. When lining up with the Dt-03? lower suspension arms, these line up perfectly. When used backwards. If you look carefully you can see that I also loped off the little extensions that were part of the original Hotshot rear suspension I believe. 

I have it all worked out...