Lehner 4200 dead!!!!

[bob2300NX]

Well I was running my motor on 12 cells in a rustler, geared 15/87. With M2K's as tires (about the size of stock stampede tires).

My motor stoped working, so I tried to take of the pinion and the screw got striped, so 15 min lator with a dremal I did get the pinion off (dont worry I used a plastic bag over the motor) but what a pain. Then opened the motor only to find the magnet is broken in half.

Any ideas why this happened? It does not make sense, I have THE WORST LUCK. First my esc went bad within 3 days of getting it, to no falt of mine.

[TheSteve]

12 cells on a 4200kv motor is pretty hard on it, perhaps it was just too much for such a small motor when running above 55 thousand RPM.(I would be nervous running the same combo in a touring car, a truck would really have me watching current draw and temperatures.)

[krisI.925]

that cell count is pretty close to the motors RPM limit, and sometimes the magnets just break just because. Its just something you gotta accept.

[Tc3basher]

any damage to the controller?

[tcolesen]

Just because the motor is rated up to 65,000 RPM's doesn't necessarily mean that it should be run that high. I would only run that high occasionally for speed runs. Definitely not suprising that it broke.

[bob2300NX]

I dont think the controller is damaged, could it have gotten damaged? Do you mean did it smoke, if so no.

Tcolesen: I thought it was the other way around that acasually you can go over the max cells for that motor?

Ok then what would be a good motor to replace it with if I do replace it? I was thinking a feiago since they are cheap. But I hope I dont have to sacurfice speed....

Thank you everyone.

[OptimaMan]

Yeah, that's pretty bad luck. I ran my 5300 with 12 cells with no problems... I even ran my 1920 5 turn with 12 cells with no problems - once, the pinion even came off and revved the motor past 80,000 rpm and no problems... I guess I'm just lucky. LOL

On a more serious sidenote, I'd agree with tcolesen - just because I motor is rated at a certain RPM doesn't mean you should be running at that speed all the time - motor will get hot pretty fast too.

12 cells are good for over 1000 watts continuous so if you want to run 12 cells, you should really consider a larger slower motor and use larger pinion gears. A "L" series would work well with 12 cells. Get like a Feigao 8L or 9L. The 8L running at 14 volts is about 42,000 rpm and since it's a larger motor, it can handle more current so you can gear it up with larger pinion gears w/o a loss of power. Plus, the motor won't be straining so much.

[AtomHeartMother]

You know....we've glued magnets back together on smaller brushless motors for our airplanes.
Might be worth a try... Depending on the design of the magnets..sometimes you can reinforce the repair with carbon fiber tow or kevlar ...very strong. Barring any serious over revving or real bad crashes, the repair should last the life of the motor.

[kufman]

Lehner doesn't recommend the use of the 4200 on 12 cells. RPM isn't the ony factor that can kill the motor. Heat can also destroy the rotor.

[joostin421]

4200 and 5300 are not 12cell motors :eek:

justin

[bob2300NX]

Well now I am thinking about the Novak setup. What do you guys think? I would not mind going to 6 cells but just like everyone else dont want short runtimes. What do you guys think, could I sell my motor (remaining motor, can and windings, no rotor) and tell them to get a rotor from rc-monster (Mike has one for ~ $30).

Like most everyone $$$$ are the problem. I seriusly am thinking of going to the Novak (even though they are slow, at least to me). I definitly LOVE the speed of 12 cells and a 4200 but if it is not going to be reliable then, I will have to compermise. No
dont a L motor (isnit it heavy)? Plus I am thinking 6 cells is better (since I will have more batteries).

I am even thinking about getting out of the hobby. Since it seems like nothing is working for me.

Any suggestions on a new motor or a CHEAP setup???

EDIT: I just thought of it, wont a feiago S or L motor be to much for my 7018?


Sorry about all the questions but I am just really confused.

[chilledoutuk]

Mate all you need is a motor with about 3000kv and 12 cells would be fine.

remember that you were running a 4200kv motor on about 14.4v which is way too close to the 65k limit.

I have had my C40 8s for years and never had a problem with it but i have always run that with 6 cells most of the time as its quite a high kv motor 5250kv.

[TimisTim]

I think people confuse power with RPM ratings.

[bob2300NX]

Anyone have ideas of what to do?

Sale my esc and broken motor for ~$130 then get a SS5800?

[chilledoutuk]

Fix your 4200 and then sell that and get a lower kv motor and run with 12 cells again but this time safely. The feigo motors are so cheap just get one of them with a kv rating of about 3000.

I dont think you will like the power of a ss after having 12 cells on a basic 4200.

[bob2300NX]

You maybe right but can my esc work with the feiago's (not too many amps)?

[chilledoutuk]

The lower kv motors draw less amps than the higher kv motors.

I would recomend the 540 12s at a kv of 2958 on 12 cells would get you a max rpm of about 42595.2 which is ideal for everday use. Also the s version would draw less current at 54 amps absolute max which i am sure the 7018 could hadle easily.

[bob2300NX]

Thank You for the advise. You are right. But after some thought I think it would be worth it to sell my motor and esc. Then get a Warrior 9918 or MGM120AMP with a 3600XL OR a 8L (like optiman suggested).

Thank You everyone.

[starluckrc]

The L can will be too heavy in the rear and adversly affect performance. A 12S can get you 50-60mph. I doubt you can handle any more than that.

Rotors also break from a motor being dropped. I'm sure things get pretty toasty inside on 12 cells on that motor (4200) as well.