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Author Topic: Motor v/s cost...  (Read 1285 times)

packy46

  • Guest
Motor v/s cost...
« on: October 29, 2008, 10:58:17 PM »

Hello Gents:
I'll try and be brief.
I am building a landing craft,length 60 in and a  beam 18 in. When I put it to the water line,I know it will be heavy,now motors, do I
go for the Graupner 720 BBTorque motors (G6372) or look for a less expensive route,if so,any ideas....
I plan on direct drive with a pair of 3 in. wheels (approx).
Thanks
Tim
 
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Sandy Calder

  • Guest
Re: Motor v/s cost...
« Reply #1 on: October 30, 2008, 09:03:08 AM »

Hello Tim.
Three questions:

A fan motor from a car could do the same job as a 720 BB torque but I'm scratching my head as to what you are actually doing.Driving a sprocket wheel?

What RPM do you want for direct drive 3 in. wheels?
That would be a help!

Do you have a ball park figure for the power you'd need? It's just that if you go down to a smaller motor you can get them with compact inexpensive gearboxes,unlike the 720.

You'll get more feedback once this is moved to another category.(brush/brushless)

Regards
Sandy Calder
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packy46

  • Guest
Re: Motor v/s cost...
« Reply #2 on: October 30, 2008, 03:24:04 PM »

Sorry Sandy:
Trying to be brief,only ended up giving you folks little or nothing  to work with,again Sorry.
My landing Craft will be rather heavy,with ballast and all running gear,maybe 25/30 lbs.(approx).
The boat I'm told with the right motor should be able to run direct drive,= motor,shaft,wheel (prop).
Sandy,as you see I'm assuming my LCM8 will need the same power ratios as a tug,meaning the need for torque,not speed.
Being new to scratch building,this put me into a whole new realm of calculations, and head scratching.
Thank for sticking with me on my quest.......
Tim
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Sandy Calder

  • Guest
Re: Motor v/s cost...
« Reply #3 on: November 01, 2008, 09:58:37 PM »

You mention cost. Motors from a car scrapyard have have the same torque as your motor.

You might be breaking a few pencils agonizing over motor rpm and power calculation but there is nothing to that at all.The motor is giving maximum power at half its no load rpm.
The unknown quantity is what prop pitch and size is right for your craft.
Regards
Sandy Calder
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packy46

  • Guest
Re: Motor v/s cost...
« Reply #4 on: November 02, 2008, 12:25:48 AM »

Hi Sandy:
Calculation...
So I went with some knowns, got the 720's,  couplers, shafts, and props, at least this way that part of the build is taken care of.
I can now pay more attention to boat itself.
This is my first attempt at scratch build,a boat any way,did trains for years,but trains don't run out in the middle ponds.
I have great respect for you Gents,and my new found hobby...
Thanks for your help.

Tim
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