Mechanical Brake Big problem

[RC-Monster Mike]

Originally Posted by azjc

I have only used motor braking in my BL rigs and I have never had any damage like you have in the picture, including setups with more power than you are using, IMO the problem is more deep rooted

Agreed. I doubt the mechanical front brake had anything to do with the failure. By supporting the rear of the motor on the chassis, the chassis flex will affect gear mesh(chassis flexes between the rear brace and the center diff - the front and rear of the motor is supported on opposite sides of this flex and assumes the load in this configuration). Not saying this is the root cause, either, but it is likely a factor. An aluminum front diff bulk will strengthen the mount the way it is(front plastic allows some flex, but at least everything attached to the diff flexes together without the rear brace). The way those teeth broke(at the very bottom of the teeth), my guess is that the gear mesh got jammed tight from flex/mesh change and was a factor in the failure. That pinion is likely a year old as well, so fatigue likely played a role in the failure as well (our current pinions use better steel than that version as well).

I use 50% brake strength as start point, and then dial in(out) the rest on my radio. I also use a brake curve. I don't think mechanical front brake will actually do anything for you - a hybrid setup with mechanical rear would allow you to effectively tune bias, but a front mechanical brake only won't allow you to get more rear brake or a rear bias. Motor braking by itself will allow the diff to bias the braking power, but the diff is usually unloaded somewhat to the front when accelerating, so when you hit the brakes, the front "feels it first" anyways and a mechanical front brake alone is counter-productive IMO.

[Shark413]

Mike, that was an old picture of the motor/mount. I just wanted to show the spacing needed to clear the Kyosho brakes. In another post you mentioned that bracing the motor at the rear would cause problems when the chassis flexes. I agreed with you and removed the rear brace before the truggy was ever run. So the stripped pinion must be due to some other problem. I find it hard to believe 75% motor brake could shear off metal teeth like that. I only have this kind of problem with my truggies (Kyosho ST-RR and CEN TR), I have stripped a few plastic spurs but only this one pinion. My buggy has not suffered from this type of problem. I appreciate all the feedback.

[Shark413]

Still experimenting with the brakes, I will turn the motor brake way down, disconnect the front mechanical (remove the servo 3rd channel wire from the rx) and run motor brake only, to see how it feels. I guess I will need to wait for the Ofna Hyper 9 before I can go with full mechanical brakes again. The Hyper 9 has the rear brake mounted at the rear diff so motor clearence won't be an issue. I have also been playing around with making a rear mechanical brake mount that works similar to the Hyper 9 that I could try out on my Kyosho's. Just not enough hours in the day.

[lincpimp]

I have a feeling that Mike's slipperential will help with pinion/spur issues, and drivetrain shock on landing. On the mech brakes issue, motor brakes do work reasonably well, but hard braking does cause the weight to shift over the front wheels, thus unloading the rears, and thus the diff, limiting braking. The hybrid setup with rear brakes, and motor braking sounds the best, but I would prefer to use the slipperential center diff before realy racing hard...

[MetalMan]

Originally Posted by Shark413

Still experimenting with the brakes, I will turn the motor brake way down, disconnect the front mechanical (remove the servo 3rd channel wire from the rx) and run motor brake only, to see how it feels. I guess I will need to wait for the Ofna Hyper 9 before I can go with full mechanical brakes again. The Hyper 9 has the rear brake mounted at the rear diff so motor clearence won't be an issue. I have also been playing around with making a rear mechanical brake mount that works similar to the Hyper 9 that I could try out on my Kyosho's. Just not enough hours in the day.

Why wait for the Hyper 9?

http://www.rc-monster.com/forum/showthread.php?t=12295

[Shark413]

Metalman, thanks for the info. I knew there were other buggies out there that used a rear diff brake setup. I am just trying to get one to work on my Kyosho truggy.