tricky_dick

hey guys,

Iam new to the RC world but have an application which requires some high thrust/low speed jet drive set up with a very low overall profile. Looking to move a model that weighs about 150-200 lbs at about 6-10mph. Model has high drag, on purpose, much like a tug boat. i have found a lot about jet drives-one particular one from Australia claimed 210N or about 47lbs of force, which would be ideal. is this a realistic number? How much thrust do these bigger boats put out if i were to hold them still? I assume there would be some cavitation if the model was not moving at speed...? Also have seen brushless DCmotors which look to spit out 1-2HP. Iwas thinking to couple one of these with a series of 60-70mm props in a tube to add maximum thrust, much like a jet drive but with a series of furbines. or very much like a vertical lift pump for pumping water out of a well.

Well, any help would be appreciated.

Please keep in mind that i am here because a trolling motor/small outboard will not work. Really need a solution with high thrust in a tiny, tiny package.

Thanks for any thoughts.</p>

Umi_Ryuzuki

Not a whole lot is required to move that much weight.
However, moving it at the speed you want, or getting it up to that speed as
quickly as you want may be an issue.

Toesup built "Mustang Sally" with a 3:1 drive ratio and runs a 3.75" propeller on
a 10lb boat measuring 18"x8"(a springer) hull. The boat can produce about 4lbs of thrust.

http://www.rcgroups.com/forums/showp...postcount=1980

I run the same size boat, "Ryoko", weighing 8lbs, direct drive running a 1.75" propeller.

Both boats can push 900-1200 lbs of weight.

Some of the heavy cruisers we run weigh up to 100-120 lbs. They are run with two
Pittman 12-24v motors, maybe 2" propellers and they travel a brisk walking pace.

None of these are jet drives, but the thrust and RPM are well below what you seem
to be specifying, and they all move at a reasonable pace.



Mustang Sally and Scoot
[youtube]http://www.youtube.com/watch?v=oO_SYiPUvxo[/youtube]

Ryoko and the SDM tug
[youtube]http://www.youtube.com/watch?v=83z4y9UV4QA[/youtube]


Mustang Sally putting pumpking in motion.
Super Springer "Scoot" with SDM tug in the background
Stock Springer "Ryoko" pushing pumpkins.
Ryoko and the SDM tug wrangling a large gourd.

tricky_dick

Thanks Umi Like you say, moving it is not the problem. getting it to go the speed i want is. to do this, i think i need about 30-50lbs of thrust.

Lets try phrasing it like this. Is it possible to get 30-50lbs of thrust from an RC type setup?