Wheel_Nut

I'm surprised no body mentioned this, but the main power loss with old motors is due to loss of spring tension when the brushes are worn down. Putting new brushes that have full length will create more tension on the spring and allow the motor to generate more torque. Cleaning the commutator is a good idea as well.

I doubt the problem is with RCMart. Even if something unexpected happens, they will eventually despatch everything and I found their customer service follow up is 100% if there are issues. The problems are due to demands on international shipping. Even getting parcels though customs these days will have a large backlog and could be stuck for weeks. Further delays to get air service. If you want to get something quickly, you probably need to pay for FedEx service.

Gear differential used on the Frog, Fast Attack, Wild one, Hotshot series. The bevel gears are too small and makes unwanted crunching noises. CC-01 steering is probably the winner, although the CC-02 bump steer also looks bad.

Independent front suspension would be easier. Many people have adapted the WT-01 gearbox into independent suspension, such as my Hornet from 1994. Maybe you could duplicate the same WT-01 gearbox at both ends, but with universal drive shafts at the front. Another idea I had is to use two TA-01/ Mantaray rear gearboxes, and make a dual motor truck, then all the drive shafts and uprights should be off-the-shelf. Even the 4WD Mantaray drive-train with a shortened drive shaft could be adapted, as a single brushless motor should really have enough torque when geared at 1:11.27.

Once you relocate the battery, I wonder if you can move the steering servo to the RHS of the car. That would eliminate the bellcrank and one of the steering links.

It seems the chrome rims were the right choice, but I missed a trick by not putting yellow spotlights.

The ranking for the vintage buggies is like this: 1) Fox 2) Grasshopper II (Super Hornet, Rising Fighter) 3) Grasshopper (Hornet, Storm Dragon) 4) Falcon (Bear Hawk, Blitzers, Stadium Thunder) 5) SRB (Superchamp, Fighting buggy, Rough rider) 6) Madcap / Astute 7) ORV (Frog, Subaru Brat) 8) FAV (Wild One) 9) Striker (Sonic Fighter) I marked highly for models that are well designed and rugged.

When it comes to control and traction of the M08, you may have a point about the rotational intertia caused by wheel spin. This is a dynamic system, so it seems a bit too simplistic to expect that "motor reaction force = powerful drive under acceleration". Motor acceleration and the vehicle acceleration will only be matched while there is perfect grip from the tyres. When you have directional stability issue there is also the gyroscopic reaction force, and lateral "weight transfer". If the car spins to one side, the gyroscopic reaction will apply additional load to the outside loaded tyre, which is a destabilising effect. As the car will break traction at the rear, its will over-rotate and the gyroscopic reaction force becomes even greater. That seems less of a problem when using front wheel drive because it causes understeer, which will slow the yaw rate. I thought it was logical to have the motor rotate in the opposite direction of the tyres so these forces can be cancelled as much as possible.

Thanks for doing analysis and posting your diagram. However I want to question your conclusion that all 3 "would try to lift the rear tires off the ground at the moment of acceleration". If you add up the total rotational inertia of the motor, gears, wheel, tyres all combined, I think the net overall reaction may be the opposite. Because the wheels and tyres have larger diameter and significant combined weight, they will more than cancel out the reaction force due to the motor. So I'd expect all three are applying increased force on the rear wheels during acceleration. It will be closer to a neutral situation where opposing forces are partially balanced. When it comes to cornering stability, I'm more concerned about what happens when you stop accelerating, or when the braking occurs. That's when all 3 will try to lift the rear wheels off the ground. In the case of Tamiya M08, they have made the "weight transfer" more exaggerated by having the motor rotate in the same direction of the tyres. I thought it was a very unusual design choice to be honest. Now I'm going 'out on a limb' to suggest that's the reason why people find it inherently unstable, or more unstable than the M06. Do you know any other successful racing buggy using a rear wheel drive chassis that has the motor rotation in the same direction as the tyres? The ones I can think of are 80s Tamiya buggies, and some drift cars, so that's not a good reputation for corning stability. I'm happy if you have more evidence or counter examples that can prove or disprove my suggestions.

4WD cars tend to understeer on power, so its common to use use a rear stabiliser bar or firmer rear springs to make the car more responsive to the steering. Rear wheel drive cars normally don't have that problem, and will be more likely to snap around if you are too hard on the power or brakes. The first rule is to do everything you can to maximise the grip on the rear which normally means soft springs and dampers. Its not the opposite of what you described. For the M04, I'm using the stock front springs, but pre-loaded so its hard up against silicone tubing. The front compliance is mostly in the tyres, except on impacts caused by bumps. If you can get shorter and harder front springs, you would not need to preload in the same way and have potential for good performance.

My guess is the mid-motor will be more balanced in cornering, but the rear motor *may* have better on a standing start. I would build the Mid motor version. IMO the handling problems of the M04 are caused by the soft front suspension. On my M04 I put silicone tubing on the inside of the front shocks, so I can preload the front springs and largely limit the suspension travel. Less front grip, but more predictable handling. It tends to lift the inside front wheel on turns.

Sounds like Tamiya business model has always been based on this. Tamiya are plastic moulding experts. That is where they can generate the most profitable returns, or at least cover the overheads of their operations. Selling the little carbon fibre and alloy hop-up parts at inflated prices is like icing on the cake. The customer has to pay once for the kit, and a second time for the hop-ups.

For any alternative battery layout, I just hope it will properly support the roll-hoop. Driver protection shouldn't be compromised.

Tamiya have made significant design revision in the pasts. You can see how many things were changed between the Hotshot and the Boomerang. The original Hotshot had very poor access to the electronics, so they re-designed the chassis. The cost and time to develop tooling today is much less today than back in the 80s when it had to be machined manually. Modern manufacturing makes if feasible to develop products quickly and rush to market if they choose to.

To me the price isn't the biggest issue. I got the impression this design was rushed onto the market without much critical evaluation. I will wait until they release version 2 with a revised chassis layout.