• If you log in, the ads disappear in the forum and gallery. If you need help logging in or getting registered, send request to: webmaster@southernairboat.com

Belt or gear redrive

Southern Airboat Gallery Archives

ccbird
AIN'T SUMMER TIME GREAT
I love my quick slick
In the marsh
ss boat
Airboat Races
Whitebear

Whitebear

Silent Prop
R. I. P.
I have operated belt reduction redrive units but I have never in person even seen one of these rotator boxes. I assume they are gear or chain drive? Can someone give me the lowdown and comparisons? Advantages and disadvantages and cost and does one hold its used value better then the other? Longevity of the unit?

Scotty
 
I have owned and ran a belt drive, rotator, stinger and Roberts (converted GSO aircraft box). I have also installed a clutch on a rotator and have run up 1,500HP on gear boxes. To me there is no comparison the gearbox is the only way to go. For several reasons 1 the belt drives don’t go high enough with their ratios 2 the belt drives weigh to much 3 with a belt drive the prop and motor torque to the same side so when running a belt drive you need experience or a large boat or both. A gear box turns the prop in the opposite direction of the motor thus canceling out some torque roll. Hands down any 2.38 or 2.68 gearbox will out perform a belt drive no doubt about that. Also the smaller the boat the bigger the advantage get’s a large 16ft or up the difference is not as drastic because the boat is so heavy and becomes less responsive and already torque rolls due to it shear weight. So my recommendation is if your hull is under 15ft run a 2.38 or 2.68 gearbox 16ft or over it doesn’t really matter. It all comes down to what you want and what you plan on using your boat for.
 
Thanks Whitethunder, good info. The opposing torque idea is valid regardless of experience as it comes to me its the right thing to do. I definately like the lighter weight idea as well.

What I'm gathering about the ratios is that less mods need to be done to the engine for airboat use. Is that where your going with that? Makes another positive case im my mind.

Ok the other things im concerned with is value retention, or will it be a $100 White elephant ya cant get rid of 5 years on?

Next is reliability over years of service? Will it last 10 years or is it a 2-3 year thing ya need to overhaul. I assume there must be some type of backlash setting with the gears or do they just get sloppy over time?

My use: I don't race boats. Im a hunter/frogger/pleasure rider. I like to go out for an all night frogging trip, frog a while, make a pot of coffee, frog a bit and say its too late I'm tired and head home hahahahahahah. I'm not hard core anything, just love to run the boat and show folks the marsh and get out of town. I don't mind long dry run stretches but most boats can be made to do that regardless of the engine/drive. I dont like to abuse an engine or push it to its limits. I just emailed Doug Hamant for a quote on a 14' hull so my next boat will be 12-14 feet not any longer for sure.

Scotty
 
For around 6 years now I have been running higher ratio boxes if you do this it will enable you to run more prop because of the torque multiplication. I say use the gearbox as a torque multiplier not a RPM enabler. I have done extensive testing and had several people debate me until they tried it. A 2.68 ratio box will plan out at the same RPM or less RPM’s than a 2to1. I run a 2.68 ratio then run a ton of pitch I don’t even let the motor turn 5,800RPM. The higher ratio gearboxes allow you to run so much more pitch than a 2to1. Also less prop RPM is also much quieter because the prop speed is lower.
 
Let me see if I got this right. Say a 5000 RPM engine with a 2.68 to 1 ratio will spin the prop at about 1865 RPM? and at this RPM you can get equivalent push as a 3k RPM prop because you can use so much more pitch? Just using round numbers here.

Oops, is it 2.68 to 1 or 2 to .68?????????

Scotty
 
Thunder, we've had this conversation several times before and what you're not telling Whitebear is that you have to give up almost 30% of your horsepower to a gearbox under acceleration due to the mechanical loss, and that the loss from a belt is something on the order of 5%. Or that the belt is quieter than the gearbox, and virtually trouble free for thousands of hours of operation.

Those aren't my numbers ... they're from the manufacturers. The ONLY advantage I see to a gearbox is that they're lighter than the Franklin belt units, and the new Blue Lightning belt unit will take away that advantage.

Lower gearing means spinning the engine more = more engine wear and less fuel mileage. And I'm still not convinced that turning a bigger prop makes much less torque effect than my belt turning a somewhat smaller prop. I turn right easier .... you turn left easier. So? :?

BF
 
FEather thats good info to have too. Im still waiting for something about longevity/maintenance/value etc.

I guess its pretty obvious I havent remained current with the technology lately. Takes a lot of *stupid* questions to catch back up.

IM really impressed with the forum. Years ago this kind of thing in no way could have existed hahahahah. Used to be different camps of thought wouldnt even speak to eachother. Kinda like a Methodist wouldnt say hello to a Baptist in the ABC package store.
 
Whitebear, two Baptists don't even recognize each other in a liquor store ..... :lol: !
 
I have never had a failure with a gearbox and I'm making substantially more horsepower than most people. I do know somebody with a belt drive that can't floor his boat or he will shred his belt and he has done it and I have friends who witnessed it. I have two friends that have logged more time on their boats than anybody I know they both have rotators and neither has never had a problem. I have never seen a rotator fail. I even asked everybody on this board if any of them have, their answer was no. I have also never seen a belt drive even come close to the performance of a gearbox. I have known 1/2 a dozen people who ran a belt drive then switched to a gearbox and all of them stated the gearbox was leaps and bounds better. Not a one of them has switched back. All of these people who preach that belt drives are better I doubt have ever owned a gearbox. I also believe the 5% is B.S. because anything that is a torque multiplier can not be that efficient. If anybody out there has a Rotator or Stinger and would like to trade for a Franklin belt drive please let me know I will pay all the freight both ways. I have one I'm dying to get rid of. As for my RPM theory for some reason nobody believes until they try then everyone say’s wow that don’t make sense. I have switched four boats from a 2to1 to a 2.68 and all four cruised at a lower rpm ran the hill better and got better fuel economy. Remember I don’t sell gearboxes and I don’t care with one is better I only care what has performed the best for me during testing or running.
 
Thunder, if I'm wrong I'll be the first to admit it. I'll get you to show me how that works one of these days.

BF
 
In my case I went 2:1 with 507ci Cadillac and pitched prop several times. I tried with engine rpms at 5200, 5000, 4500, and 4200. I kept it at the 4200 setting as it is much better than the other settings. Cruising rpms varied from 3100 to 2100 rpms too. I'm running a 78" 3 blade wide Sensenich and the #2 setting gets me to 4200. Anything other than the Cadillac and I would have run a higher ratio. I have to agree with Waterthunder.
 
You must log in or register to reply here.
Back
Top