Just a Rocky Project (Formerly "My Kyosho Developed Yokomo Envy")

[HS-YZ250]

Though it's probably going to take a while to finish, because projects I undertake normally do and this one has been running longer than any other so far, I've gotten to the point where my "Super Rocky" is starting to resemble what I had envisioned.

The story behind this car:

Way back around 1991/92, or maybe it was a year or so later, I was big into racing my Losi LXT (and maybe my Pro SE, too) when my Mom had a conversation with the woman I was mowing lawns for about my hobby. The woman mentioned her son had an RC car, too, and I asked to look at it. Her son came home one day and dug out this Rocky. He had left it in a closet after last using it a few years before going into the military, and didn't see himself using it again, so he gave it and his pit box to me.

Disappointed it wasn't a racer like I had, and that it was noisy, had a hacked body, and handled horribly, I only swapped electrics into it a few times to get it to run. One of those times, however, was the last time I actually entered a race about 1995/96 (Phil Hurd Raceway, Savannah, Ga). I raced it dirt oval, with many looks, and broke it in a heat race (differential outdrive stripped), having to finish with my Pro SE, so again it sat through college and my racing years (Quads, not RC cars). It still has dirt on it from that race.

After quad racing died down, I got bored so I brought all the cars up to my house and started looking on eBay to fix the Rocky. I, then, got the idea of trying to make it better. This is when I learned of the Turbo Rocky and it's independent front shocks, so I added Turbo Rocky uprights and found a set of RC10B3 (maybe?) shocks. The idea was that I would put as much suspension as I could and see what I could make it do. But, parts were slow to obtain and, again, it sat while I worked on other things (I get distracted easily) until I pulled all my cars out, again.

This time I cleaned up and upgraded the Losi's and got a YZ10 (another thread), a car I long wished I could afford. All the while, I watched eBay for Turbo Rocky parts, specifically looking for the front gear cover for the front shock tower. Earlier this year, I hit pay dirt, and now I can put add a shock tower. Here's where it stands. Shortly after getting the YZ10, I thought it would be neat to make the Rocky look like it, so I started looking at lowering the body and adding a YZ10 style wing to the back. Big holdup right now is getting shock towers sized for the RC10 shocks made.

Just this one picture for now. I'll post more, later, if anyone wants to see specific things.

[HS-YZ250]

Can anyone recommend a hex drive replacement for this screw on the Rocky? Guessing it's a 3mm thread, around 13mm long. The trick is that it seats flush in the top of the upright and has a slightly smaller than standard head diameter, so a search on McMaster didn't yield any good results. I want to replace with something easily obtained so that I don't have to worry about rounding out the phillips head.

Thanks!

[EvolutionRevolution]

Buy a regular 3mm hex head screw, stick it in a electric drill, and sand down the head until it's small enough?

[highwayracer]

I just finished a rocky restoration and when I was going through all of my screws (from my Kyosho hardware box) and I noticed that they used different size heads. At some point, Kyosho changed this...and it was something that I noticed years ago. This was the first time that something didn't "fit" because of the Rocky's upright design.

[DennisM]

If You don´t mind swaying away from original, I´d suggest a socket head hex screw?

Edit - like others allready suggested

[jwscab]

it's hard to depict from your photo, but couldn't you just use a standard cap screw that uses an allen hex? If not, as Evo-Revo stated, put it in a drill or drill press and sand/file down a screw to fit. A standard hex cap screw will be pretty hard though, so a stainless steel one might be easier to modify. modify a few of them for spares, and you should be good.

[HS-YZ250]

Yeah, I want to get away from the original hardware, where reasonable, for ease of maintenance. If you look farther back in the picture, some years ago I managed to find shoulder bolts for the knuckles that only needed a couple of nylon washers to make work. Seems the OEM stuff rounds out easily.

I forget exactly what the diameters are, but I believe the Kyosho head came out to 5.2mm and is a close fit in the upright, where a standard M3 socket head hex screw is something like 5.5mm or better. This is just going off of specs, though; I haven't tried anything yet. I had found a couple of "small head" screws, but were about $4 a piece and too short, anyway.

I wonder if I can chuck up the bolts in metric nuts in my power drill and spin them against my grinder, to save my fingers.

Another thought was to forgo a head and use a setscrew. I would lose the ability to torqe the screw, though.

I'll try a couple of things and report back.

[Coelacanth]

I'm not too familiar with the Rocky, but don't the uprights use special kingpin screws top & bottom, not regular screws? Kingpins have a wider, unthreaded section above the threaded ends that fits snug inside the hole of the uprights, and you lube it with some grease. Is the Rocky upright assembly totally different?

Kingpins.jpg (12.5 KiB) Viewed 3651 times

Kingpins.jpg (12.5 KiB) Viewed 3651 times

[jwscab]

yes, definitely use a grinder if you have one. It may be in fact that you need shoulder screw like coelacanth suggests, too, I'm not familiar with the rocky.

[DennisM]

I'm not too familiar with the Rocky, but don't the uprights use special kingpin screws top & bottom, not regular screws? Kingpins have a wider, unthreaded section above the threaded ends that fits snug inside the hole of the uprights, and you lube it with some grease. Is the Rocky upright assembly totally different?

Kingpins.jpg

He refers to shoulder bolts in his last post. Must be the kingpin screws.
The screws he´s looking for now is the fixation for the outer end of the upper suspension arm - if I´ve understood it correctly.

[Coelacanth]

I'm not too familiar with the Rocky, but don't the uprights use special kingpin screws top & bottom, not regular screws? Kingpins have a wider, unthreaded section above the threaded ends that fits snug inside the hole of the uprights, and you lube it with some grease. Is the Rocky upright assembly totally different?

Kingpins.jpg

He refers to shoulder bolts in his last post. Must be the kingpin screws.
The screws his looking for now is the fixation for the outer end of the upper suspension arm - if I´ve understood it correctly.

Ahh ok, I think I get it...I have some Kyosho front arms that are like that, I think for the GP-10 or Spider...the threads are only on the end of the bolt with the head, the rest of the bolt is unthreaded. I was using the picture as reference, thought the screw he was holding vertically was the vertical screw that goes into the upright.

If that's indeed the situation, I'd use spacers & hinge pins with e-clips instead of a threaded bolt.

[HS-YZ250]

After all that wondering, turns out a 3mm button head will go right in. So much easier than those phillips screws! Too bad they don't make 3mm button head plastic screws, too.

Now to figure out what to do about shock towers. Anybody ordered their own custom made shock towers? Fibre-lyte never called back.

[HS-YZ250]

Hey! It's been a while! Busy with other things. Don't know how much time I'll be able to put on RC cars, again, but we got a new toy at work that will help this project move, if I can get a handle on SolidWorks, find the right parts, and solve a few issues. Here's a picture!

[HS-YZ250]

Not much of an update, just a shot comparing parts. Going to add a bridge to the end of the arm when I do a final version. The latest moved the lower shock mount in and reduced the width of the leading fork of the arm, and shortened the lower leg of the knuckle carrier to help clearance issues with the wheel. Still some contact at steering extremes, but I think I can shim out most of what I need to and make minimal cutouts for the rest. The wheel contacts the steering knuckle as well, which are swapped right and left so that the knuckle arm touches the suspension arm minimally at full droop.

By the way, I'm working around ZX6 front wheels (RB6 and B44 wheels didn't work out), and the CV joint on the modified side is a 73mm long LA257 out of a ZX5 FS; a new set popped up cheap on ebay.

I'm probably going to look for a set of next size smaller front shocks to replace the RC10T (I think) shocks that are on there. Have two more sets the same length that are doing nothing.



Meanwhile, the next thing I'm looking at is the chassis. Going to be busy with work over the next couple of weeks, and the work toy is down for repairs, but I think if I can work out a good solution, here, then I'll have most of this figured out. I originally planned to do a graphite double deck setup with an underbody, but now I'm thinking I'll try and do a tub with a single lower plate, plastic sides for rigidity, and braces between the tub and the gearboxes. I'd like to, anyway. We'll see how far I get. I want to make the chassis length fixed and use a spring loaded wheel to tension the chain, minimize contact points, and get rid of the chance of slack from a crash. Of course, I'm also going to have to figure out a steering system, too. Here is a picture starting to figure out a chassis layout on the parts car. Even going out to the full width of the body and using a saddle pack, space is tight.

These aren't necessarily the electrics I'll run in the car, just gauging space. Thought it'd be funny to mod this like I want, and then run a brushless LeMans motor, if they're still available.

[HS-YZ250]

Spent all my free time over the Christmas break fighting with the CAD program and laptop that desperately needs to be re-formatted, but I am finally to where I can start laying out new parts and see if my tub idea will work. Well, need a couple more simple things. Below is an image of what I have in CAD. The blue shaded parts are Rocky parts that I'm keeping, the orange are replacement parts I've made or am working on. The upper plate shown is only for spacing, at the moment. If the tub idea doesn't work out, it'll be turned into a functioning chassis part.

I'm sure I'm going to have to do a couple of iterations, at least, for each part, since I used a dial caliper to measure molded parts and didn't take the time to account for holes opened up for threads, or draft on the parts. I think the nose plate to rear gearbox relation will be problematic.

Going to be getting ready for a race day after New Year's day, maybe two, so it'll be a few weeks until I can start printing parts, I think.

Question(s):
*I'm considering going Lithium Polymer and Brushless with this. Are LiPo saddle pack cells the same outside dimensions as the old SubC saddle packs? (Overall length, width, and height)
*What is the trend for batteries in RC? I.E. Are cars moving away from LiPo saddle packs in favor of another format, or are the LiPo saddle packs still commonly used? Like the ZX6 wheels, I want to use something that's going to be around for a couple more years.

Thanks!