re re Steroid-shot running 3s lipo :)

[a2t22 0]

Hello all,

My 1st post on the forum, Im glad I found this place !

Ive been a tamiya nut since the 1980's, and always drooled over the hotshot. I bought my son 1 (and me!) for Christmas a few years back and we have been enjoying the car since. It has actually been quite durable up until recently when the 540 motor finally gave up.

So, I swapped in my 3300 kv brushless motor and speed controller from a RTR RC10b4.2 kit that i bought a while back. I also picked up a few 3s battery packs just for fun. The 3s packs were pretty ridiculous in the RC10, hitting 60 mph +. However with a 2wd chassis, it was hopeless.

Happy to say that the 3s pack actually works well in the re re hotshot, on loose surfaces where the tires dont hook up all at once.

Im wondering if there is a metal 50t spur gear (gear that mates with the motor pinion) to replace the plastic, as Im burning that out now. I will probably go back to the 2s pack, but this is incredibly fun. It runs across the backyard grass pushing wheelies at 30-40 mph, Ive never seen a hotshot do this ! It can sling rocks so hard they nearly break the house windows. On a beach it will shoot rooster tails 15' in the air. Completely insane, but ofcourse the gearbox is not up to this on anything but very loose surfaces. On the street, this steroid shot probably hits 45 mph or more. It will shred the tires in a few runs, so I try to keep it only on loose/soft surfaces while running 3s.

So .. any help on a metal 50t spur gear ? Perhaps 1 from another model that could fit ? Im running a 17t steel pinion and that is working well and limiting the over-torque during the brutal acceleration. If 1 is not available, perhaps I will make 1. Im a product design/development engineer with extensive CAD and in house machining capabilities, and have made quite a few SLA's from high strength steel. We could easily print a gear from 17-4 PH or even titanium. Cost for just 1 would be around $500, but for 50 pcs, it would be about $50 each. For that matter, we could make nearly anything for this little buggy if people wanted them...

Any other re re upgrades for this worth checking out ? Ive seen the metal front/rear control arms but Ive honestly not had an issue with the plastic versions. The suspension is very floppy and not capable of running on a real RC track with big jumps, but for neighborhood bashing/baseball diamonds/beach sand its just fine. The super griper tires are perfect. Ive only just now broken the front bumper, and that took nearly 2 yrs of some pretty hard crashes so I dont believe the metal version is needed there. Ive never broken the plastic wheel carriers, although the nice blue metal ones do look nice.

I need to upload a video of this 3s monster in action. Just waiting on the new 50t spur gear to come in. All the other gears in the diff looked nearly new. No wear anywhere, except to the stock soft aluminum 15t pinion which wore out and then stripped the spur gear.

[Nitomor 2122]

Nice first post, welcome to the forum, of course we don't believe anything you've said until we see video evidence of this monster

I bet it flies on 3S the 3,300kv is running at 36,630rpm, enjoy!

[LongRat 616]

I don't believe any metal transmission gears are available for this chassis but honestly I don't think they would increase durability. A good upgrade you could design and make would be a slipper clutch for this car. You would probably be able to sell quite a few if you wanted to as well.

[wolfdogstinkus 1893]

You need a steel pinion gear,, the Tamiya aluminium one is rubbish,, wears out on the stock silver can motor and chews the spur.

Someone else will have to advise on pitch.

[Terz1 745]

Welcome to the club. Your hotshot sounds amazing.

We all need to see it in action. Definitely post up a vid or two. Love to see those rooster tails.

[Flerbizky 225]

Welcome to the club. Your hotshot sounds amazing.

We all need to see it in action. Definitely post up a vid or two. Love to see those rooster tails.

I haven't been here long enough to welcome people, but great first post - and what Terz1 said \o/

[a2t22 0]

Yes vids/pics coming. I went ahead and ordered new transmission bag yesterday, I will replace all the dogbones and universals while im in here. They all have over 200 hrs run time on them, I figure its prob time. I am waiting on a 17t steel pinion gear coming from hong kong, its been in the mail for weeks now. Not sure if that will solve the spur gear problem or not, you are exactly right about the soft aluminum tamiya pinion gear. Hoping that with a proper metal pinion, the spur will last much longer...

regarding the slipper, if you have cad models, or even sketches, i can turn them into 3d printed metal parts (using a company that also puts parts in military aerospace projects). they print from 17-4 and titanium and have already made gears for automotive racing applications that far exceed anything we're talking about here. how many would want them ? I'd be game for it. Estimating $100 on qty 100, wouldnt exceed that anyways, hopefully less..

whats really strange is the tires are not glued to the hubs, which actually creates a sort of slipper clutch in itself as the rims slip on the tires. Of course sometimes this causes the tires to jump off the rim, so not ideal. Like i said, this set it is really only usable on very soft surfaces. And dont stand behind the thing when it launches or you get a face full of dirt and rocks pelting you !

Should be back up in and running in a week or 2. have to travel for work but all should be here later this week so when i return i'll reassemble and hopefully not kill it too quick. Im guess on the street it will hit about 50 mph running the 17t. When my kid takes over the controls, I just dial back the speed control adjustment on the radio to about 30% Its still 2x faster than the car was out of the box. My front yard will soon be all dirt, these supergripers are merciless.

[LongRat 616]

Interesting coincidence you work with metal 3D printing. I am also a dev engineer, I work for the only company in the UK making metal AM machines. We manufacture the machines and also make parts on them. I wouldn't consider RC transmission parts to be that suitable for this technology, either from an engineering or cost perspective really. I think these parts would require at least some secondary machining operations, in which case it would be better to machine them from solid in the first place.

I don't know of anyone who has designed a slipper clutch for the Hotshot, I certainly haven't although I have been considering it. I think the best way would be to make parts to allow an existing commercially-available unit to be retrofitted in. That way, spares like pads etc can be much more easily sourced.

[a2t22 0]

Sounds like you should have an "in" for us then to make the parts :)

You know, you must test each machine before delivery, perhaps that would require running 50 or so custom gears for us ?

The man'f Im working with has already made small automotive engine gears being used in racing environments. They perform great so I see no reason why AM couldnt be also used for the little hotshot gearbox. Perhaps the teeth are too small ? However, Im running an automotive project through them now with very tiny, thin gear teeth (originally molded of 6/6 which we redesigned from proper metal). I will see how that goes, they see no reason why it wouldnt work (they've already looked at the CAD models and quoted cost). I will let you know how it goes, the gear Im now making is much smaller than the hotshot main spur or diff gear set.

Your point is well taken regarding modding the gearbox to accept a drop in ball diff, like from an associated B4.2 (I happen to have that laying in front of me right now). The pitch and spacing to motor shaft are different between associated and Tamiya. Is there another brand you were considering ? Seems like it would take at least 1 custom gear to swap in an off the shelf ball diff.

Im all ears for suggestions, I'd be happy to donate my CAD/CMM expertise for the better cause. My day job is boring, I should of been a Tamiya engineer.

[berman 5315]

Would love to see this hotshot on 3s

I have a wild one with a 4000kv on 3s.

[Darat76 265]

if you do get around to installing a ball diff, be careful when setting it up, if it's to loose the drive plates will spin and put a flat spot on the balls, which then causes it to have notchy diff action, once that has happened you need to pull it out, strip it down, clean it out, and use a fresh set of balls in it, learnt this the hard way myself...

[a2t22 0]

Ive got everything except the 17t pinion coming from hong kong ... been waiting like a month now. I dont think its coming ...

this is killing me ...

i will look on ebay and find another steel 17t tamiya pinion i guess.

[a2t22 0]

Would love to see this hotshot on 3s

I have a wild one with a 4000kv on 3s.

would love to see a wild one on a 4000kv 3s ! you got a youtube channel of that insanity ?

I really like this forum, wasnt sure if you guys were going to show me the door like some other forums when i tell them the stupid stuff i get up to

[berman 5315]

https://youtu.be/zGdEjts8cAM

[Percymon 2184]

https://youtu.be/zGdEjts8cAM

Tasty !

[Gruntfuggly 562]

Gotta love beach running...

[Frog Jumper 3656]

https://youtu.be/zGdEjts8cAM

That's hawt!

Terry

[a2t22 0]

some day i will figure out how to upload videos, ive taken several, some in slow motion with my iphone that are pretty cool. you can see the front yard grass getting ripped to shreds.

anyways, it didnt exactly take long (maybe 5 or 6 runs) to completely trash the plastic 50T drive gear. which mates with the pinion gear and diff gear. I switched over to a all metal 17T pinion gear, its obviously far too much for that 50T plastic gear.

So ... rather than be smart and just go back to 2s battery, I figure maybe I can retrofit a better 50T gear but harvesting the plastic smaller section and bonding it onto a proper metal 50T, like this 1 - http://hobbiesdirect.com.au/traxxas-50t-32dp0.8mod-spur-gear_

Question being, is that Traxxas 50T even metal ? Or also plastic ? But maybe a higher strength plastic ?

I run a complete CNC machining center, so I could have 1 of my guys machine off plastic 50T section of the Tamiya gear and make me a little adapter that would bolt onto the Traxxas 50T. Then we would just epoxy the plastic center section with the diff gear and bevel gear onto the metal traxxas gear. Or better yet, 3D print the center section diff/bevel gear with the mounting provisions to the Traxxas gear as 1 piece, then simply bolt the 2 together. If we wanted to get really crazy, just 3D print from metal the whole shabang as 1 piece.

This would give me the 50T metal gear i need to mate with the pinion. Im not worried about the bond strength, it would be stronger than the plastic gear anyway. Also think the bevel and diff gear would hold up just fine, as those are much smaller in diameter. We would of course just have to center the plastic middle section onto the 50T metal gear such that runout was not a problem.

Still thinking about a ball diff, too. Hard part is mating up the diff with existing gearbox walls, and dog bones. I suppose we could make all that stuff, too. Eventually we will have a pretty durable hotshot. You guys should see this thing running up/down the street, it probably hits 45 mph easy maybe faster.

I will figure out how to upload the vids from my iphone to youtube when i get some time.

[Percymon 2184]

I'd guess that Traxxas gear is plastic, possibly carbon reinforced, but I doubt very much its metal.

There are a few aloy counter gears for Tamiya cars from aftermarket companies, but I've yet to see a 20/50T counter gear thats suitable for the Hoshot. There are quite a few suppliers of 15/50T counter gears (for the ClodBuster which is also 0.8M), so it may be worth askign a couple of the suppliers whether they have a 20/50 option or could make one.

[Wooders28 4718]

Would love to see this hotshot on 3s

I have a wild one with a 4000kv on 3s.

Love to see the vid too.

I have a dark impact with a 5700kv on 3S 😛

Upload a vid once it's out of hibernation and I can get someone to hold the camera.

Fitted a hardened gear to the slipper shaft to try and get some longevity out of the gearbox.