Barn find Rocky, belt drive conversion

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cas22
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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

Dug it out, but its pretty rough, guess i could run it on my novak T4
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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

Also found these factory SCR saddle packs, pretty rare now.
I think i got them with my mates optima mid TOMS conversion kit way back in the 80's
They had yellow sce versions come out later as well but ive never seen one in person.
Cells are long gone internally, so will either repack with NiMh or preferably retrofit LiPo saddles inside the case.
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20210412_183449.jpg

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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

Has anyone tried running a brushess 3.7v settup likr the newer 1:12 carpet pan cars?
Suspect it may be enough for the old transmission on the rocky, and the single saddle fits awesome on the chassis, if i repacked the kyosho case.

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Re: Barn find Rocky, belt drive conversion

Post by Coelacanth »

I wouldn't recommend it. 3.7V isn't enough juice for a 1:10 off-roader. I'm running a 1S/3.7V LiPo setup in my RC12L3 pan car Buick Grand National car. For that chassis, 3.7V should be fine, but it requires sourcing a special 1S-compatible ESC, and I've learned those aren't cheap. Most inexpensive ESCs are meant to run on 2S or more LiPos, and you run into issues with low-voltage cut-off when your voltage drops below about 6 volts.

Build and info on electronics used:

https://www.rc10talk.com/viewtopic.php?f=77&t=17837&p=209028#p428512
Completed projects: CYANide Onroad Optima | Zebra Gold Optima | Barney Optima | OptiMutt RWD Mid
Gallery - Coel's Stalls: Marui Galaxy & Shogun Resto-Mods | FrankenBuff AYK Buffalo | 1987 Buick GNX RC12L3

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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

Foung a hobby king turnigy super shorty, only 2600 mAh but hey the original ran 1200mAh sc cells, will fit nicely on the chassis

Turnigy nano-tech Ultimate 2600mah 2S2P 90C Hardcase Lipo Super Shorty Pack (ROAR and BRCA Approved)

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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

Little bit more work today, cutting up a perfectly good glass top plate.
Jigging around to fit the "super shorty" Lipos, sourced some mounting blocks from MST Short battery holder set 210451,
Cut and shut it to suit the shorter pack, this also clears the chain/belt on the bottom of the chassis.
Necessitated drilling and countersinking the top radio plate.

You can see the JazRider optima universals, I fitted these by swapping out the 10 x 5 x 4 mm bearings for 10 X 5 X 3mm bearings, giving 2mm of clearance to fit the rocky. The clamp and pin drive hex's too.
Replaced the suspension ball with 5.8mm alloy threaded units to tidy up and tighten the suspension.

Still not too happy with the shocks but have ordered some others to try just about 4mm too short, could use longer cups on the bottom to compensate.
Fitted new standoffs between the chassis and top plate with conical washers, and fitted after market shoulder screws and wafer washers on the steering.

I have ordered some belt pulleys from a Kyosho V1 R4 gas car, hopefully they will fit and finally allow me to swap out the chain drive.
Also dug out a 240ST and rebuilding it too.
Sourced a higher idler gear too from ebay in Spain, this will allow me to run a 17T pinion for more top end.
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rocky 4.jpg
rocky 3.jpg
rocky 1.jpg
rocky 2a.jpg
rocky 2.jpg
rocky 1a.jpg

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Re: Barn find Rocky, belt drive conversion

Post by Retro rc »

Looking good Craig 👍🏻

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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

Finally had some deliveries today, stuff is taking so long to arrive,
the hard to find 32/22 idler came in from Spain, this will allow me to run a 17T pinion, and the Kyosho gas car pulleys.
Like the look of them, and same brand is nice too.
There is a shaft discrepancy as the Rocky shaft is 5mm, the V one 777 pulley bore is 6mm, sourced some thin wall precision tube to adapt this.
The size looks good too compared with the chain drive. 27t belt, 28t
This is important to get the clearance under the battery correct.
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rocky pulley 2.png
rockey pulley 1.png

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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

Battery Cradle mk2, tricky to fit the "super shorty" LiPo above the chassis so that it clears the belt underneath it, stuff all clearance, found this touring car cradle which I can cut and shut for the correct width and it elevates the cell tight up under the top plate, about 7.5mm clearance now, if this doesn't work I may have to go to a low center of gravity (LOW CG) shorty LiPo, which are 18mm thick rather than the 23mm standard hard case units.

Also grabbed a couple of closeout touring car suspension swing arms, ball raced M3 threaded, still trying to engineer a more elegant steering mechanism, as you know this is the rocky's Achilles heel. Thought i was getting close with the HPI F1 steering unit, but just too thick, no matter what ball cups i try.
I can cut and file these to see if i can make them work, at a couple of dollars each I'm not worried if i bin a few in trial and error.
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rocky cradle.png

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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

Fitted up the new pulleys today, used the 5mm/6mm precision tube, quite tricky without a lathe.
Used a tube cutter initially but this distorted the tube no matter how gently i cut, ended up having to use a cut off disk in the Dremmel and lots of patience.
Front pulley had no shaft left to circlip to, so with a lot of measuring i had to clearance one of the belt teeth on the gear as where the pin alignment was it didn't line up on the recess, then drilled a 2mm hole through, and carefully drilled partially to 2.5, and tapped the top of the pulley M3 to take a grub screw.
This means that once the 2mm pin is aligned and home, the grub screw beds it down and it cant come out again. approx 10mm wide pulley, and 4.5mm in on the inside edge for the pin.
Was reluctant to take this on as I had no spare pulleys, but came out mint.

The rear pulley worked out easier as I had a longer shaft to use for retaining. Fitted a 0.5mm shim on the gearbox side and by slotting the 6/5mm tube insert I could slide it home.
I was experimenting with fitting 12mm hex front bearings on my Ultima and had some driveshaft clamps from BZ-222 that i didn't end up using.
They couldn't be used on the Kyosho driveshafts as they were the wrong diameter.
Luckily the thickness (5.0mm) and the clamp hex coupling nipped up the rear pulley perfectly against the drive pin, It was snug anyway
Also put the c clip back as additional protection, but i don't think its going anywhere.
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rock gear 1b.jpg
rocky gear 2b.jpg

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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

When Jeff did an awesome job cutting the chassis and top plate for this project i asked him to cut me a rectangular section of G10,
I was messing wit the idea of getting rid of the gearbox alloy top plate, as its not required as heatsink for the mechanical speed control resistors any more.

Trimmed and filed to suit but I didn't anticipate the idler gear running proud of the gearbox top.
The alloy casting has a recess to allow it.
As I have now fitted the smaller optional idler gear I had another look and it was very close to clearing, but still not enough.
I slotted out the G10 in the right place to clear this gear and carefully refitted the speed control finned top flush .This covered the recess, and looks factory when the body is fitted.
Not sure if I like it yet TBH, Id grown accustomed to the alloy, but hey, modelling is tinkering and seeing what fits., no worries to swap it back over at any stage anyway
You can see the clamp and circlip here too.
On with the shocks tomorrow.
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rocky gearbox cover.jpg

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Re: Barn find Rocky, belt drive conversion

Post by Dadio »

I get why your in two minds over the gearbox top cover , it's kind of iconic of the Rocky , the G10 will be lighter and probably stronger but the alloy looks cool :?
If a jobs not worth doing then its certainly not worth doing well.
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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

Started playing around with the steering bell crank, these are notoriously weak and a terrible design from the factory, Tried all sorts of options but in the end settled for a more beefed up unit from shapeways. It was just too difficult to get the dog leg angle and throw range correct.
As you can see there were two options available, a factory copy to take the 5.8mm Balls or the one I opted for with holes ready to accept ball ends (M3)
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steering 1.PNG

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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

While i was there i replaced the aluminum post, which is 6.4mm o/d to 3mm i/d.
Found these flanged bearings that I bought to make belt tensioners out of, 6mm o/d, x 3mm i/d x 3mm deep (1mm lip)
I had some precision stainless tube left over from the drive gear sleeves and cut a spacer to suit.
Ball raced steering. I know its over the top for this old sloppy car, but why not make the improvements if you can?
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steering 2.PNG

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Re: Barn find Rocky, belt drive conversion

Post by cas22 »

Planning to fit these 5.8mm alloy pivot balls too. From some drift car I think, "Slidelogy SDY-0187" I've used them on the turnbuckles in other places on the rocky, really tightened things up, and very low profile. I will try a few other pivot balls first, but the clearance is tiny under the rocky gearbox. Even looking at 4/40" associated stuff as its smaller, seems wrong to put on a kyosho kit.
Attachments
steering 3.PNG

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