YR-4 custom buggy conversion

[AllenB.5979]

The front suspension is supported by a pair of 62mm Gmade diaphram shocks. I can't say enough about these shocks. For the 32$ price tag you just can't beat the quality. I wouldn't suggest using the shock oil that comes with them as it seemed to be oil based and really cheap. Once filled with a quality silicone based fluid they are super smooth. They do take a while to purge all the air but it's totally worth it. This Yr-4 bumper is not permanent. It will soon be replaced by a Yz10 piece or something like it. I may just go with a repro piece.



You can also get a good look at the hinge pin brace I made from a pair of Tamiya Avante suspension ball ends and some threaded rod. Being that I'm using 20+ year old plastic Yr-4 bulkheads this reinforcement was absolutely necessary. At some point I may try to source an aluminum set from a Yz10.

[AllenB.5979]

A closer look at the custom idler pulleys I made with the front belt In place. Worked out perfectly.

[AllenB.5979]

The rear set up also includes HPI MT2 arms and HPI hub carriers. Once again only some spacers and HPI hinge pins made a perfect fit. I had to narrow the hex adapters for the rear so the Losi wheels would fit the shafts. Also had to trim the top linkage hole for clearance but nothing to tough.





For the rear I went with a set of Gmade 75mm diaphram shocks. I used Traxxas linkages both front and rear for my top links. They are nice and tough, came in the length I needed and I was able to pick them up at the local hobby store. Nice tight ball ends with no slop sold me. Here is also a good shot of the rear hinge pin brace. Again, Tamiya Avante suspension links and threaded rod. I plan to add at least a rear stabilizer bar like the one I have for the short arms. I have to pick up some wire to make it and while I'm at it I'll probably make one for the front. For the wing mounts I kept with the theme of Tamiya aluminum pieces.

[rccars4sal]

WOW! Just beautiful. It inspires me to get going on my custom. Your car looks really pro, and durable enough to run hard.

[AllenB.5979]

Just an overview of the whole car. Something I didn't really talk about was the steering system. I am currently using the Yr-4 setup which has good range but I'm not 100% happy. I did add an adjustable center link for Ackerman adjustability but it could be better. My biggest gripe is having to use tiny old style ball ends. As you know, on todays motocross, I'm sorry RC tracks those probably won't hold up. I've got my eye on a ball bearing Yz10 set up on Ebay. We'll see...

[AllenB.5979]

WOW! Just beautiful. It inspires me to get going on my custom. Your car looks really pro, and durable enough to run hard.

Thank you very much. I haven't built anything for years and it's nice to finally get back into it. I would really like to build something completely custom from the ground up. Maybe soon. Thanks again!

[AllenB.5979]

Check out my gallery. I made a kind of hot dog about 9 years ago after trying to sell a nib yr4. It got outfitted with a baldre body.
I also bought some spares: Second hand runners. And ran in the tc class with the same chassis you have. The links to the build treads are in the gallery too.

Please find us some modern arms that work. I'd like to build another one but don't like the pricing on 91 works arms.

These are the HSP arms I had put on the car originally. Pretty much identical to HPI arms for an Rs4 car. These fit with spacers although I did need to carve small 45° notches as you can see in one of the cross bars to clear the bulkhead mount. Once done they fit perfectly with a full range of swing. They were not really weekend by these notches as the plastic is still thick and it's not really a super high stress area. A bit of work but a super cheap alternative to works arms. They require HPI Rs4-3 dogbones or cvd's but again... cheap parts. Not a perfect solution but usable for sure.

[Mr. ED]

Mmmm, I don't think I'm gonna hunt for those.
The geometry looks wrong for the front:
Drive axles are swept, the cut-out for the C-carriers seems too shallow, shock mounting points don't seem to line up right for the shock tower... Same issues I had with the df03 front arms.
Df03 rear arms worked well for me. Maybe with different carrriers and axles. I'd have to read my old post to be sure.

[AllenB.5979]

Mmmm, I don't think I'm gonna hunt for those.
The geometry looks wrong for the front:
Drive axles are swept, the cut-out for the C-carriers seems too shallow, shock mounting points don't seem to line up right for the shock tower... Same issues I had with the df03 front arms.
Df03 rear arms worked well for me. Maybe with different carrriers and axles. I'd have to read my old post to be sure.

No, you're right. I had them mounted with the HPI carriers. And it does pull the axles a bit forward. It's too bad the MT2 arms are so long because they really are good. Straight axles and good geometry but I guess if you're not changing the carriers you may have the same issue with the front. I didn't try to fit them with the Yr-4 carriers so I'm not sure. When I have the opportunity I'll search for a perfect fit. I'm sure there's one out there.

[Mr. ED]

It should be fun to model up a new design and get it 3d printed. Something allowing for 12 mm hex type wheels and standard length cvd.
But it could easily grow more expensive than a set of 91 arms.

[Lonestar]

Love it despite the mechanical flaws as pointed above! Shelf engineering rocks

Now - how does she run, mister?



As usual, kudos to those who build these things!

Paul

[AllenB.5979]

Love it despite the mechanical flaws as pointed above! Shelf engineering rocks

Now - how does she run, mister?



As usual, kudos to those who build these things!

Paul

Thanks Paul. Much appreciated. As with most cars like this it's still a work in progress. I actually was just working on a ball bearing steering plate this evening to fix the steering issue. What I was talking about with Mr. Ed was the first set of arms I tried. They didn't work as well as I had hoped. The ones I have on now fit great with no axle sweep. I'm actually really happy with them. They are just a little bit long for ROAR rules. I'll be posting the steering mod soon. Thanks again!

Btw... Love your thumbnail! Have you got any little Lunch Boxes running around yet?

[AllenB.5979]

It should be fun to model up a new design and get it 3d printed. Something allowing for 12 mm hex type wheels and standard length cvd.
But it could easily grow more expensive than a set of 91 arms.

That would be awesome. I definitely think the cost could be offset by the potential market. I see a lot of old yoks on here and I would be willing to bet people would love to run without the concern of breaking expensive vintage parts. Only problem is that I'm probably not skilled enough to do the CAD design. I've played around with some CAD programs but I don't know nearly enough to do something like that. Could be a good reason to learn though. Something to think about.

One other thing. I need some info on the slipper you have on your Dark Dog project car. I would love to add a slipper to this car but I don't want to change the center bulkhead / motor mount. Will the center shaft fit the Yr-4 block? Also is the rear drive pulley separate or integrated with the back slipper plate? I would like to find a way to keep the M2 pitch rear belt if possible. Do you think it's even possible to find another like yours if it would work or is it one of those rare parts that's impossible to find? Thanks for any info you can give! Much appreciated.

[Mr. ED]

I'm no expert on the subject but I think that it's the slipper of the works 91 and later. At least 2 of the second hand yr4's I bought in Japan had this type. The pulley is indeed part of the backplate. There are hardened optional ones but i think most were soft alu.
You'd need an M2 version.

The front pulley runs on one way bearings.
Your centershaft mount should be fine but you may need another centershaft, maybe a different bearing too.

I think I can do a design that is easy to make and adapt. But the only way you'd sell anything is by keeping it dimensioned just like the original. The market in this case is mostly consisting of people who want to restore to original.

[AllenB.5979]

I'm no expert on the subject but I think that it's the slipper of the works 91 and later. At least 2 of the second hand yr4's I bought in Japan had this type. The pulley is indeed part of the backplate. There are hardened optional ones but i think most were soft alu.
You'd need an M2 version.

The front pulley runs on one way bearings.
Your centershaft mount should be fine but you may need another centershaft, maybe a different bearing too.

I think I can do a design that is easy to make and adapt. But the only way you'd sell anything is by keeping it dimensioned just like the original. The market in this case is mostly consisting of people who want to restore to original.

I definitely agree about the original spec arms. That would be a good option. Like you said though, that could quickly get expensive. Only way it would be worth it is to offer them for sale.
My only thing is that I just don't think print quality is high enough yet for a restoration grade part. Even what I've seen from the prototyping companies. Certainly good enough to run but the cosmetic aspect is nothing like molded parts. Then there's strength. I have doubts that an arm of original dimensions would have the strength needed in print form. What I've seen is others doing this having to make thicker parts adding material in order to match the strength of molded parts. I guess it's like they say. If it was easy everyone would do it! Thanks for the info on the slipper. I just don't know the subtle differences between the cars well enough to just start ordering parts on a whim. I'm sure you know better than me so advice is golden. Thanks again.
Now to post this steering plate I'm working on...