direct drive vs. gear reduction
04-22-2008, 01:09 AM
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direct drive vs. gear reduction
hey all, I am the process of gathering parts for a sport boat that I am building, for the missus.
I have a Kyosho Viper hull thats gutted, I a have a 700 bb turbo motor. I am scrapping the sub-surface drive in favor of a surface peircing drive.
I am planning on using a flex drive but I have laying around a gear reduction drive (2:1) from a Traxxas Villan EX.
Would this work (ok I know that it would work)
But could some one help me out with atvantages/disatvantages of a gear reduction. I hear that I could spin a larger prop, but how would this translate into performance?
Or should I stick with the flex drive.?
Very much thank you.
I have a Kyosho Viper hull thats gutted, I a have a 700 bb turbo motor. I am scrapping the sub-surface drive in favor of a surface peircing drive.
I am planning on using a flex drive but I have laying around a gear reduction drive (2:1) from a Traxxas Villan EX.
Would this work (ok I know that it would work)
But could some one help me out with atvantages/disatvantages of a gear reduction. I hear that I could spin a larger prop, but how would this translate into performance?
Or should I stick with the flex drive.?
Very much thank you.
04-22-2008, 08:07 AM
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RE: direct drive vs. gear reduction
Hi Joe,
The Viper runs stock with a 550 motor direct drive, subsurface on 6-8 cells and is a nimble little boat.
Fitting in a 700 motor (and 12-14 cells or the Lipo equivalent) is not something I would recommend without strengthening the hull.
Frankly I think the Viper is a bit small to handle that kind of power...
As the hull isn't stepped, you might aswell go for a solid shaft, as non-stepped boats need a bit of propangle to run well. The flex shaft gives you more flexability in the set-up, so I'd stick with that.
I would not use gears, the 700 will most likely strip them after a short time, besides that, a 700 in direct drive is perfect for a 12 cell set-up, driving a 45mm prop (Graupner K-series, 2318.45). Speed in the 40mph range, depending on set-up.
You'll need to reinforce the bottom and transom,specially under the motormount, the weight of the motor and the pounding on the water will cause the hull to crack under the stress if not properly reinforced.
Besides that, if you plan on running sub-c cells, you'll also need to reinforce the hull under the cells and isolate the ABS from the heat of the cells, as they heat up under load, sufficiently to make the hull sag , once the boat is out of the water after a run...
You can glue in strips of ABS to reinforce the hull, a lot of work through the small hatch(es) in the Viper, taking off the entire top would most certainly help.
Glass cloth and epoxy is another option, but again, the top would have to come off in order to apply that properly, specially the first layer of glass cloth, using Acetone and a brush.
Regards, Jan.
[edit] the 40mph range might be somewhat optimistic I've only gotten a 12 cell boat that fast using a very light, very well tuned Mono-2 stepped hull and it took me a year to get there...
The Viper runs stock with a 550 motor direct drive, subsurface on 6-8 cells and is a nimble little boat.
Fitting in a 700 motor (and 12-14 cells or the Lipo equivalent) is not something I would recommend without strengthening the hull.
Frankly I think the Viper is a bit small to handle that kind of power...
As the hull isn't stepped, you might aswell go for a solid shaft, as non-stepped boats need a bit of propangle to run well. The flex shaft gives you more flexability in the set-up, so I'd stick with that.
I would not use gears, the 700 will most likely strip them after a short time, besides that, a 700 in direct drive is perfect for a 12 cell set-up, driving a 45mm prop (Graupner K-series, 2318.45). Speed in the 40mph range, depending on set-up.
You'll need to reinforce the bottom and transom,specially under the motormount, the weight of the motor and the pounding on the water will cause the hull to crack under the stress if not properly reinforced.
Besides that, if you plan on running sub-c cells, you'll also need to reinforce the hull under the cells and isolate the ABS from the heat of the cells, as they heat up under load, sufficiently to make the hull sag , once the boat is out of the water after a run...
You can glue in strips of ABS to reinforce the hull, a lot of work through the small hatch(es) in the Viper, taking off the entire top would most certainly help.
Glass cloth and epoxy is another option, but again, the top would have to come off in order to apply that properly, specially the first layer of glass cloth, using Acetone and a brush.
Regards, Jan.
[edit] the 40mph range might be somewhat optimistic I've only gotten a 12 cell boat that fast using a very light, very well tuned Mono-2 stepped hull and it took me a year to get there...
04-22-2008, 01:54 PM
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RE: direct drive vs. gear reduction
Joe,
If you have the 8.4v 700, you will see around 32mph on 12 cells. If you have the 9.6v motor you will be in the high 20's. Run 700 motors direct, they don't have a lot of RPM to begin with.
Ryan
If you have the 8.4v 700, you will see around 32mph on 12 cells. If you have the 9.6v motor you will be in the high 20's. Run 700 motors direct, they don't have a lot of RPM to begin with.
Ryan
04-22-2008, 06:15 PM
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RE: direct drive vs. gear reduction
Thanks for your replys. I can tell that the hull is flimsy and had planned on re-enforcing it with fiberglass cloth and resin or z-poxy.
As for the tips on heat, that is one thing that I had not considered. Wierd since I usually check the temps on my SV27.
This is an older version and has quite a large hatch opening so working on it should not be too much of a problem.
The hull measures 24" from transom to bow. I will be running a 8.4V 700 motor on 12 cells.
I am new at this and am using this as build experience, plus a cool boat for my wife.
Thanks again for your input.
As for the tips on heat, that is one thing that I had not considered. Wierd since I usually check the temps on my SV27.
This is an older version and has quite a large hatch opening so working on it should not be too much of a problem.
The hull measures 24" from transom to bow. I will be running a 8.4V 700 motor on 12 cells.
I am new at this and am using this as build experience, plus a cool boat for my wife.
Thanks again for your input.
