29" MEAN MACHINE SAW BUILD: TWIN C/R LEOPARD MOTORS, HOW MANY ESCs?

[JIM MARCUM]

I'm building this Aeromarine MEAN MACHINE for P Offshore Cat class SAW racing. The plan is to use twin counter rotating Leopard 4074 2200KV motors with 3/16 stinger drives, (2) Nano Tec 5000mAh 65C batts, and (2) Turnigy/Seaking 180A ESCs. As Octura only has the following props in L/R config, I'll start off with X442-2 props, and move up as needed to X447-2, X450-3, and X457-2.

I think the 180A ESCs would be able to handle the max prop load, but I'm curious whether I could run both motors off (1) Turnigh 240A HV?

The "plan" is flexable. The goal is to hit mid 90s MPH or higher.

Any thoughts, suggestions? JIM

[jimi911]

I think, in IMPBA, you cannot run twins in SAWs (I believe you once could in Q or greater class) and I am pretty sure no twins in NAMBA.

Looks like a fun setup tho :)

[photohoward1]

I think you can unless that is a new rule. Open classes not spec. Just no more than the allotted cells. He is only allowed to run 4s. The Motors or ESC must share batts. Can't run 4S to each Motor. That's 8s. Even if each Motor sees 4S.

[jimi911]

I think it is a new rule, cuz that's what I thought to Howard. I looked it up and got this from the new IMPBA rules.

Class Definitions, voltage limits and restrictions*!**Class Voltage limits *!**Allowed Motor(s)*!**Style/Type (note 1) Number of*!**N 1.2 to 7.4 Any 1*!**P 8.4 to 14.8 Any 1*!**Q 15.6 to 22.2 Any Any (note1)*!**S 22.8 to 29.6 Any Any (note1)*!**T 33.3 to 37.0 Any Any (note1)*!**

Note 1:*!**Some class(s) may limit number/type of motor.*!**Some class(s) may limit battery type.*!**
So any number of motors over Q unless noted in the specific class:

Specialized Fast Electric Classes
Tunnel
General
Records and racing will fall into the N,P,Q,S,T classes
Boat Specifications
1. Hull will conform to the catamaran definition covered under technical
specifications.
2. Boat must be inboard powered with only one motor

Enter debate on IMPBA posting updated rules ... lol.

No idea on NAMBA ... I ain't a member

[properchopper]

Jim, I'm not going to say anything Jay, Jump in-you're far enough away

[photohoward1]

Tony no Opinion. Your letting me down. (going to Phoenix this year?)

[JIM MARCUM]

Aw come on Tony. Stir the pot for me. JIM

PS: Current NAMBA rules for P class state: "Any amount and/or size of motors, any endbell, bearings, and magnets. Power Limits: 10.1 to 15 Volts nominal, any chemistry. Maximum of 2 packs in parallel. Maximum capacity of 10,000 mAh." The way I read it, I'm allowed (1) 4S pack per motor. NAMBA feedback welcome.

[properchopper]

Tony no Opinion. Your letting me down. (going to Phoenix this year?)

There's a reason. You should be able to figure it out, Howard !

Yes on Phoenix; wouldn't miss the chance of driving your boat which I think is mine - Oh wait; mine's white this year. And wait 'till you see the Jersey skiffs ! Me + Pat + (hopefully) Ted & we got a race

Zi6_0458.jpg

(You know you want one)

[LarrysDrifter]

Im going on assumption here, so I mean no disrespect, but it seems you are running 4s with your set up? If so, from my experience, you will need more rpm to reach your speed goal. I had a 32" twin with 2800kv motors on 4s each with ABC 1816-5 props. ( I think thats the model number)? Anyway, I reached 81.1mph on gps. It was turning 41,440 rpm, so you might want to look at some hotter motors...maybe in the 3000-3200kv range. Thats my opinion anyway, could be wrong on the kv reccomendation. My boat was NOT legal for sanctioned SAW racing by the way. It would have been considered an 8s boat. Fluid can give you lots of set in stone info regarding whats legal and whats not.

[photohoward1]

IMO. each Motor on a 4s pack is an 8S boat. Now technically you could parallel the power and then share it and it is a 4S boat. (aren't the rules great?)
You can do what you feel is right but I think you are opening a huge can of worms.
Go for it. I do think you need more prop or RPM though.

[JIM MARCUM]

OK. 4S2P, two motors, and 5,000 mAh each batt. My head is starting to hurt!

As to more KV/RPM, I ran a Leopard 3660 4650KV motor 4S2P in my Miss Geico with a V940-3 (40mm X 2.98" pitch) prop. It drew enough amps to melt the ESC/Batt leads off - and I use 60/40 silver solder! Two 3860s running X430 (30mm X 1.652"), or X442 (42mm X 2.310) props might work. Or??? JIM

[LarrysDrifter]

Of course you melted the leads!! That was a bit more than extreme. Did anything survive? Thats close to 70,000rpm with A LOT of pitch.

[RaceMechaniX]

For NAMBA it's a legal set-up. You can run as many motors as you like, but you are limited to 4 cells and 2 parallel packs with a total capacity of 10,000mAh.

We have a guy "rearwheelin" or somethingl like that run a 4 motor conquest in Q I think but had to run only two packs with one pack per set of twin motors.

If it doubt, read the rules.........


Tyler

[steveo]

anyway run 2 controllers you going to see high amps using one wont work not if you are going to be pushing to the limits of your electronics

[JIM MARCUM]

Tyler, I've read the NAMBA rules: basically it's 15V max, max 2 packs in parallel, or 4S2P, 8 cells total. Was "rearwheelin" running his two 4S batts in parallel? If not, he was non-compliant with the rules. Whether you run 4S2P or one individual 14.8V pack per motor (2 motors) the total voltage & cell count are the same. But not in Parallel. That said, I'll run a 4S2P config as that is clearly within the NAMBA rules & will have no impact on my top speed.

LarrysDrifter, Amazingly, both the Leopard motor & the SeaKing 180A ESC survived with no damage at all. Although the SoCal FE guys a Joe's Lake saw some smoke coming out, it was just the ESC/Batt insulation frying. The motor "stuttered" & didn't rotate after it was retrieved & examined. We all thought the ESC & or motor was fried, but it was because one of the 3 ESC/motor wires gave up the ghost. I don't know how many amps I was drawing, but it must have been huge. The SeaKing 180 ESC is amazing!

PS: Stevo, pushing the limits is what I do. JIM