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Hopefully finish up wire terminations and paint the body over the next few days, and this thing will be ready for its maiden voyage. Not sure if the tires will stay on the wheels, but will find out. Everything takes so long now; stupid Spring and nice weather forces me outside!

Quick question: neither of my parts cars had a front anti-roll bar. Is one really needed?

No....but its cool and brings the value up

coxbros1 wrote: ↑Sat Apr 17, 2021 11:36 pm No....but its cool and brings the value up

Good deal! This one isn't about value.

Next question: 27T or 17T? One side of the brain says one thing, the other side another.

Considering those tall rear tires and that its a six gear, I'd probably keep the motor milder.

Unfortunately, many 27T race motors don't like tall gearing either. The advanced timing doesn't play well with tall gearing.

I'd suspect that something like a 21-23T modified would work best for bashing around, and don't over-time it.

Maiden voyage went well outside of the Monster Jr 27T not happy at all and letting some of its smoke out. It also got about million degrees. I got rid of most of my motors awhile back, but am looking to see if I have anything around that would be more suited for the task.

Waiting to get another body and get it painted and on before taking it off any sweet jumps. My re-re was supposed to be here by now so I could scan the decal sheet and get a new one printed off, but with the USPS, it is unknown when that will happen.

morrisey0 wrote: ↑Sun Apr 18, 2021 3:28 pm Maiden voyage went well outside of the Monster Jr 27T not happy at all and letting some of its smoke out. It also got about million degrees.

I bet it wasn't happy. A 36° motor, with a six gear and tall tires is a horrible match. It appears that you are running in grass, which is even worse.

Trinity Ex Spec 21x1 12* more better? That is all I have sitting around above 17T. Number of windings and timing is a bit beyond me. I will take some time this week to learn me on the subject.

I want to get the body on it before I decide if the big tires stay or not. They aren't helping performance wise, so if they also look a bit stupid, I will look for other options. Just thought I would try them out, and since they actually locked in, that was a little bonus.

Its probably better than either of the other two. If it is like my 21T/12° Speed Spec motors, it is simple to make it adjustable. Just remove the locating tab from the endbell. I don't normally run more than 4-6° of timing on my mods.

I have an extra six gear transmission laying around, so I did some fiddling with spur gears and gear covers. With the original clear cover (looks like yours):
- An 84T spur clears easily.
- An 86T spur rubs slightly, but there was enough slop in the holes to tweak it enough to just clear.
- An 87T spur rubbed, period.

An 84-85T spur and small pinion would lower the gear ratio a little.

I have an 86 spur sitting around so I can see if it will fit under the Parma cover. If not, I will source a 84 - 85. I have an 81 on there now.

I did some quick math.

My JConcepts Hazzard RC10 tires are 3.15" tall. Your RC4WD tires are 3.83" tall. Those are the numbers I used to calculate the effective ratio.

An 81/18 spur and pinion (re-re) with the 1.83 transmission equals 8.24:1 final gear ratio.

But when combined with the taller tires, the effective gear ratio is 6.78:1.


Now. An 84/15 spur/pinion and 1.83 transmission equals 10.25 fgr.

But with the taller tires, the effective gear ratio is 8.43.



I used the Wallace Racing calculators to figure the effective gear ratios. They were made for full size cars but the math still works on smaller increments.

Since we are rightfully bringing tire diameter into the formula, can't we use rollout as an apples-to-apples comparison? Let's bring the carpet world into the buggy world!

I dove into my RC10 bin and found an unused set of what is labeled as "TR8412" tires. These seem to be some sort of vintage "You-G" tire made for buggies. When comparing them to stock knobbies, they look to be about the same thing. They are 3.35" knobby outside diameter.

The RC10 re-re manual loves 18/81 FDR, so with 3.35" tires, we are looking at a rollout of 1.28.

Running quick calcs, I can run my 3.83s on 16/86 and end up with a rollout of 1.22. I have a 17t pinion that can bring that to 1.30.

The 86t spur gear fits fine under a super thin Parma cover.

Of course the fact that I just discovered that I have a brand new set of vintage knobbies may make all this a moot point, but again, I may like the big tires when all said and done.

Two sides of the same coin. Effective gear ratio is just easier for me. And not knowing what other people know, its easier to explain.

juicedcoupe wrote: ↑Sun Apr 18, 2021 8:50 pm Two sides of the same coin. Effective gear ratio is just easier for me. And not knowing what other people know, its easier to explain.

Yea I know. Just rollout calculators are easier to find than effective gear ratio calculators, so that made more sense in my head. I appreciate your time and effort in helping me through this. I will still make it a mission this week to learn more about motor turns, windings, and timing.

I love following projects like yours! Mostly because this is how I roll ( ) also. I like to use what I have on hand whenever possible. I'm looking forward to seeing how your project evolves. I also lol'd at your comment:

morrisey0 wrote: ↑Fri Apr 16, 2021 8:22 pm So if you owned a sail rail in real life, and your neighbor had a mild mud truck on 38" swampers, you know you would have to eventually see if they would fit.

It seems like gearing for oversized tires should be similar to what is used for early RC10 truck conversions. From a stadium truck standpoint those are a typical tire diameter.

Aside from the gearing, maybe also give the wheels and rear area an examination to make sure everything rotates freely without rub or binding. Bearings all smooth and free? Also, is your motor in good condition or could it use some cleaning, brush/spring maintenance and lube?

We've been enjoying some 17 and 15 turn (3 slot) Radon 2 motors with 3000 mah NiMH batteries recently. They are so inexpensive new, I have trouble considering a 27T stock motor an option anymore.