Jet units and gearings.

[str3ngthz]

say i was running these jets, (ones in attachments)

the stock gears are 1:4

it says it reduces current drain by about 1/2

the motor im currently using is a standard 9,6v 700bb turbo on 9,6v 4000mah nimh packs

the jets have a 40 mm Ø impeller

what im wondering is; would it be wise to go too 1:2 with the gearing or maybe even 1:1 direct drive kinda thing without burning out of speed controllers etc?

the controllers are rated at 200a continuous current with a peak current of 800a; im guessing (don't know much about model motors and such but going off a car battery is 90amp ish and the wires are about 20mm thick..) that 800a = 800watts?

any advice appreciated and explanations appreciated very much so.

if you need more info i can try my best to get it for you.

[pompebled]

A reduction would leave you with an extremely sluggish boat.

In direct drive on 9,6V, the 700 Neodym will only rev at 14400 rpm, which is still not very much for these large jets, I'd run them on 12 cells at least.

Make sure the motors are watercooled well, use can and brushtab cooling.

Check the Kehrer site for more info on the max rpm for this type of Jets.

A 200A ESC is a bit overkill, but if you already have them, use them, they will barely get warm.
A 50A watercooled flight ESC per motor will do the job.

Regards, Jan.

[str3ngthz]

12v is speed control max, a friend running the same jets did burn out two of the same speed controllers by reversing the gearing 4:1

i would just like maybe 1:2 or 1:1 without blowing something or any fires onboard:-

have a fast drifter s something went wrong other day on it, set on fire middle of lake, is there any small fire extinguishers out there that can be placed inside of a model boat like you would get inside a full size real boat, as a last resort to save the hull...?

jets are graupner and cant find max rpm's

boats been built for a few months but it is rather slow running twin jets

brushtab cooling, just a water coil or what we talking here?

[GreenAmphibian]

I run two mini-jets in my 1/12 PBR powered by two traxxas Verlinion brushless motors. I have plenty of speed with 12 V li-po's.

[pompebled]

12v is speed control max, a friend running the same jets did burn out two of the same speed controllers by reversing the gearing 4:1


That's just plain stupid; by gearing up, you are making the motor run way out of it's most efficient range; the Ampdraw will shoot up an kill the ESC, and/or the batteries.

I'll post some pics of the cooling I have in mind, when I'm home tonight.

Regards, Jan

[str3ngthz]

thanks yeah i found out today he actually went through 6 £60 speed controllers before he gave up, he kept pushing to get the best performance and just burnt a hole in his pocket.

[SilentHunter]

Jeezus thats some determination