Kyosho Rocky 4wd..... I think?

[GoMachV]

That bellcrank looks cool, but its way too tall to fit. A single kyosho ball stacked on top of a .062 plate will not clear. Maybe 2-56/2mm if you could find a threaded ball.

Trust me, I'm a fab guy too. There isn't room for the normal method

[Coelacanth]

I hear you, gomachv...I think differently, of course. I don't want any car I own to be a shelf-queen, it has to run--and it has to be bulletproof, as much as possible. I need to replace all the weak links in the chain of the original design. I couldn't spend weeks modernizing a car only to have the same weaknesses that plagued the original still plague the modded car. For a shelfer, why not, just leave all the weak links as-is, nobody's gonna care. But for something you're actually running, might as well address the design flaws and try to improve them if possible.

Yeah, it's a lot of work and takes some logical thinking and re-engineering, a good example would be all the modding I did to my brother's Marui Galaxy just to get a suspension that actually works half-decent...but it's worth it for a runner, I suppose.

[Coelacanth]

That bellcrank looks cool, but its way too tall to fit. A single kyosho ball stacked on top of a .062 plate will not clear. Maybe 2-56/2mm if you could find a threaded ball.

Trust me, I'm a fab guy too. There isn't room for the normal method

I dunno...to my eyes, there's a possibility to make something like that work. You could even try mounting that L-crank I linked previously upside-down and have it so the balls and ball-ends are situated on the bottom instead of facing up...with a bit of creativity, I'm sure something is possible.

[GoMachV]

You know, if you were to brace up a unbroken one like I did my broken one, it may not be an issue at all. The area the ball pivots in is thin, and where they crack. I bent a piece of piano wire to fit very tightly against the crank in almost a complete oval, and secured it with black Cyano. Hard to see I the pics but its there.

[RichieRich]

I like threads like this. I think a sliding rack would be ideal or bracing the stock one somehow. Also, I totally hear you about using period parts. When I redesigned the steering on my Ultima to be more "standard" with the servo mounted like the newer buggies, I used vintage Lazer, Ultima and Optima parts.

[GoMachV]

Exactly! Sometimes ideas aren't "new" and i don't have a problem mounting a servo crossways for a sliding rack as the yokomo were that way, not a "new" concept at the time. A blue anodized alloy bearing supported crank.....not for me for durability sure.

[turbo scorpion]

the pivot balls snap into it, so metal is out. 3d plastic is still a bit weak. If I didnt have so many projects I would play with it a bit, but I did mock up a g10 bellcrank, and the shortest pivot balls I could find were still too tall

I am no expert but...
I saw a bullpup full auto gun made on 3D print. Also if going that route could have several spares made...

[turbo scorpion]

low profile rod ends like this with really low profile screw? along with metal or plastic substituted or fabricated part.
the one end has the ball pressed into a metal end... could allow you to use your existing tierods/solve clearance issues.

[Coelacanth]

low profile rod ends like this with really low profile screw? along with metal or plastic substituted or fabricated part.
the one end has the ball pressed into a metal end... could allow you to use your existing tierods/solve clearance issues.

I bought some of those, they're actually a lot chunkier than the pics lead you to believe. Plastic/nylon open-ended ball-ends are significantly smaller and lower profile than those alloy ones. I have some Integy units similar to those; they have 3mm threaded holes on the ends but they're probably 6mm diameter on the outside. At least, if those are similar to the ones I bought, which were blue.

You need to have a very low-profile ball & socket setup for the Optima's steering servo and steering links, and the lowest profile solution I could come up with, that was also as strong as possible, was open-end Delrin ball-ends pressed onto 4.8mm hex-balls with most of the bases cut off. You need just enough of the ball and threaded part to be able to screw it in securely from underneath. Kyosho also makes low-profile 4.8mm ball studs, those are good too.

This image shows that you don't exactly have a lot of room with the Optima for upgraded linkage, either...this shows the Kyosho low-profile ball studs on bottom and the ball cups on top are popped onto cut-down hex-balls. You could slim it down even more by using open-end ball-ends but I wanted full cups for the Ackerman linkage to limit dirt getting into the sockets.



Here's another picture of upgraded Optima steering servo linkage, it's not the best pic but you can see how you really need low profile in this location. The stock setup just has a weak steel servo rod bent into a hole in the servo horn. I upgraded it with a 3mm titanium turnbuckle, open-end Delrin ball-end and cut-down 4.8mm hex ball, screwed on from the outside (left side) with a stainless steel hex-head screw that has a very flat head. Note that even though I'm using an aftermarket alloy servo horn that's at least twice as thick as a plain plastic one, it still has a very low profile.

[jwscab]

so from what I see, it has a single bellcrank, which means the steering link is going to be longer than the lower a-arm, which will give you some funky ackermann, as well as have a larger arc radius to achieve full steering lock.

taking into account we don't want to drill holes in the chassis, you need to make a plate out of G10 that does three things:

uses the two existing holes to mount it.

slide the chain guide back

adds two places for the two sides of a rack system.

use 3mm hardware so you can use 3mm bearings. make two rack 'arms' out of G10 the fits a 3x5mm flanged bearing, so it can sit on those two screws.

connect it to a rack bar that brings the ball locations outside of the chassis by about 7-10mm, and use standard balls, and shorter steering links.

[RichieRich]

Looks like you would get massive bump steer with that setup, Coelacanth.

[Coelacanth]

Looks like you would get massive bump steer with that setup, Coelacanth.

Why yes, I did. And I corrected it shortly afterward.

http://www.rc10talk.com/viewtopic.php?f=30&t=21530&start=108

I just didn't choose the "corrected" picture because it doesn't show the steering linkage I wanted to show for this topic.

[RichieRich]

Oh yeah, I remember seeing this.

[Antonov]

Dear All, this thread is old, I apologize to bring it up... but actually, having been looking around the web, it is the best subject on the matter ! So I would think it is good to continue with it and add more information or idea.

About me, just posted:
http://www.rc10talk.com/viewtopic.php?p=459627#p459627

Now, on the bellcrank case... since I have three Rocky at home, I am very much concerned about the weakness of this keypart. And the fact that replacement is simply impossible to find.

I clearly would like to investigate and find a simple and cost effective solution to all people having the same situation. My criteria are: not genuine is not a problem, but I would avoid altering any part of the original car (bodywork, parts around it...) to make a retro fit always possible if, one day, a new release of the original part would be made possible or if 3D printing will become so popular and easy in a few years, that my kids will just scan the broken part and print a serie of 50 in a laugh !

I will post once I find some, if I find some.

I was already considering what was suggested above: using a RC10 (funny that the reference is similar to the forum's same, just by coincidence) steering bell crank. Aluminium or not... at least first trying with the cheapest I can find and see how this part can be used.

bellcrankjco2309_CROP.jpg (12.43 KiB) Viewed 1006 times

bellcrankjco2309_CROP.jpg (12.43 KiB) Viewed 1006 times

Then, using this strong base, you can work "flat in line" to add anchor-balls on each side of this part and that should work.


Another option, obviously mentioned above, would simply be to go the pragmatic approach and decide to "print" a batch of 50 pieces and sell then "at cost" on Ebay. Pressing a button to get 50 more... I have no idea what the cost would be to have a 3D file printed professionnaly by a company using hi-grade and fine-quality parts... I will try that slowly.
Will keep this post updated.

[Antonov]

here is the more refined idea... the point is to create a solid bellcrank into which can be screwed basic / easy to find / cheap components.

With this version we get exactly the same rotating ability of the parts, rigidity increase without compromising the chassis.

I will try to refine this idea and send it to production.