djr01974

I have the motor pod and was wondering if anyone can recall who made this . I'm gonna use this in my cat project that I'm messing around with , its the evx2 system .

djr01974

sorry here are the pics .

Simon.O.

I do not know the EVX2 system first hand but I do know a little about gear drives.
A quick count shows approx 30 pinion and 70 spur teeth. This gives a little bit less than 1.5:1 reduction.
Good torque and good power, depending on motor choice and cell count.
Motors ?? what is on the other side of that unit.
I have spun stock 540 cans on 12 cells ( for a while ) and had spectacular results with gear drives.
I am now about to go to a very good 600, fully cooled, on 12 cells to spin my 1.5:1 gearbox in one of the bigger boats in the fleet, I already run this motor on 10 cells with the same 'box in my CAT.
I am very keen to see more pics of that unit that you have there and the hull that you plan on dropping it into.
Keep us up to date.

n.h.schmidt

Hi That is a old MRP gearbox. They most often came in their Hydro boats and one of their Cats. With the orginal gears you got 1to 1 ratio but, with two motors. If Simon is right about the gear tooth count 30 pinion and 70 spur ,you will have 2.33 to 1 ratio . Thats a real high ratio for fast boats but can work. You will need hi reving motors to get it going . I have a couple of these Mrp gearboxes. One is for sale cheap. n.h.schmidt

djr01974

Hey simon on the other side are two titan 550 14.2 volt motors , The set up im using is in the Traxxas ex boat , its the evx2 system , 16.2 volt .

djr01974

anyone know what kind of spur gear I can use if I want to change up the ratio ?

Simon.O.

His estimate of ratio is bang on.
It is a little highly geared but can do the job.
I guess that you are looking reduce this ratio.
one option would be to go to a good hobby shop and take a look at gear wheels that are used in RC cars, I know my lhs has a good supply of them.
Alternativly you could look for a replacement gearbox unit out of a Kyosho or Academy boat, I have both sorts in 3 of my boats and all are at 1.5 : 1 and can take one or two motors.
See how ya go !
Keep us posted.
Cheers.

djr01974

I just counted the spur gear, it is 60 teeth , with 27 tooth pinion gears . Do you thing its over kill?

Simon.O.

That gives you 2.22 : 1 Not ideal, but not all bad.
You will really need some spin on those pinions for it all to happen.
In my 26" Cat I run a 2250 kv 600 size brushed can on 10 cells, this gives me 27krpm at the pinion, via a 1.5 : 1 reduction I get close to 18krpm at the prop.
Running a Kyosho 42mm x 1.4 gives me great acceleration and good speed, the motor only runs warm, it is cooled too !
Now for yours to see 18krpm at the prop you will need to run about 39krpm onto the pinion. I do not know if your motors or any brushed cans will spin to that.
Your other option is to up prop.
Before you think all is lost, consider that my little 21" mono has the same motor and 'box on 8 cells so gets about 14krpm at the prop. This little boat honks !
For you to get that prop speed with your 'box you will need to go a little over 31krpm on the motors.

I am real keen to help you here but will need some more info.
Do you know the running speed of your motors or thier kv ?
What props do you have ?
How big is this cat that you have ?? .......Got pics ???
Do you have any other motors, or are you willing to buy some ?
Is there a supplier near to you that stocks RC parts ?

I am by no means an expert on this or any matter, I do however have a bit of experience with gear drives.
Catch ya soon. [8D]

djr01974

the cat is abs its 30 inches long I don't have any props yet as I'm still putting it to together . I do have a nice three bladed prop but I haven't decided yet . I can get a bigger set of pinons if k need to

speed3-inactive

That gear box with that gear ratio will run you into trouble because you need a motor or motors that need to rev very high underloads.
540 modified motors like the trinity cobalt other motors in its class can give the rev you need but the maintenance would be very great.

djr01974

what gears should I be running than?

NitroNuisance

Titans are 15 turn I believe if that helps anyone at all? They come stock in the Villian boats, Rustler, Bandit, and Stampede XL-5 along with the E-Max trucks. I've been told their a bit overated as far as 550-15 turn motors go. This probably doesn't help much but I have a little experience with these motors in a Rustler and a Bandit before I converted them to BL systems. To me they seem to be similar to a 19 turn higher quality motor.

speed3-inactive

Honestly you need 1.5 to 1 and like 12 cells on the titans with the motors in parallel to get reasonable prop rpm without load. With a setup like this a octura x440 or a x442 should work, graupner k series prop should be a close substitute for the octura's cheap and don't need balancing. I don't know how long the motors will last with this setup but if you want to use the gear box this may be the right direction. I think a single 700sc or 700bb 8.4 would be a simpler, more reliable and more convenient if you give it a try.