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Author Topic: Graupner Jet booster 3  (Read 4964 times)

lukehallbland

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Graupner Jet booster 3
« on: July 28, 2009, 04:17:40 PM »

Hello all,

I just acquireddd a Graupner Jet booster 3 which I intend to use in a Norbert Brggen Ballfish submarine hull http://www.modelluboot.de/KITS/Kugelfisch_Ordner/Kugelfisch.html

I was wondering what sort of brushless motor would be recommended for this? I think the prop is 30mm and the hull is 15cm wide by 60cm long if that makes any difference. I'm not really that concerned about speed as I'm just using the end bit, so rather more a shielded propeller than a proper jet. If possible I'd like the keep the draw less than 20amps max as so I get a good run time on the 12ah lead acid battery. I know very little about motors and props so any help would be much appreciated.

If it helps the motor I was otherwise going to use is a speed 500 Graupner one pulled from my previous Graupner shark submarine

Thanks

Luke
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hopeitfloats

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Re: Graupner Jet booster 3
« Reply #1 on: July 29, 2009, 10:45:59 AM »

720 motor. but sorry dont know what that is in brushless. maybe its still called a 720. i'm sure someone will know.
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lukehallbland

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Re: Graupner Jet booster 3
« Reply #2 on: July 29, 2009, 11:02:14 AM »

Thanks, I have a look and see what the equivalent is.

Is a 720 faster or slower than a 500?
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Martin [Admin]

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Re: Graupner Jet booster 3
« Reply #3 on: July 29, 2009, 11:41:49 AM »

Is a 720 faster or slower than a 500?

A Graupner Speed 720 is a Bigger motor than a Speed 500, quite a lot bigger.

Is it this unit? http://www.hobby-lobby.com/basic_jet_propulsion_boat_drive_118_prd1.htm
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lukehallbland

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Re: Graupner Jet booster 3
« Reply #4 on: July 29, 2009, 12:34:05 PM »

This is the unit: http://shop.graupner.de/webuerp/servlet/AI?ARTN=2346&SessionCheck=4711&language=en

It's one of the old ones, only using it because the model shop wanted to get rid of it so sold it for 10.
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Martin [Admin]

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Re: Graupner Jet booster 3
« Reply #5 on: July 29, 2009, 01:06:08 PM »

Jet drive unit are designed to run FAST but as you are using it as "shrouded" prop, then a slower, more
sedate motor might be in order, as you say a standard 540 (Speed500/600). You will have to experiment a bit as I
couldn't find the original motor spec for the Jet booster 3, it's not the speed so much as the amount of power /
loading the drive unit put on the motor and hence the motor requirements.

Assuming that a "standard" 540/550/600 motor will work then this type of brushless motor is the sort of thing you might need.
It's a replacement brushless motor  for a "standard" 1:10 buggy car....

http://cgi.ebay.co.uk/1-10-RC-R-c-EP-Car-Truck-Buggy-540-3660-Brushless-Motor_W0QQitemZ290326343297QQcmdZViewItemQQptZUK_ToysGames_RadioControlled_JN?hash=item4398cc6e81&_trksid=p3286.c0.m14


Ebay search:  http://toys.shop.ebay.co.uk/items/_W0QQ_dmdZ1QQ_dmptZUKQ5fToysGamesQ5fRadioControlledQ5fJN?_nkw=Brushless+Motor+water&_sacat=2562&_trksid=p3286.m270.l1313&_odkw=&_osacat=2562



JET propulsion unit 3 Booster


The JET propulsion system Booster 3 (No. 2346) is designed for the CONDOR-9 catamaran ferry in conjunction with the reversing mechanism (No. 2346.1), but can also be fitted to many similar model boats.

Specification
Length approx. 140 mm
Length incl. steering
nozzle and reversing
mechanism approx. 190 mm
Width approx. 42 mm
Height approx. 50 mm

Product information
The only difference between the JET propulsion
unit 3 Booster and the JET propulsion unit 2 is the modified inlet duct.

The kit contains: inlet duct (2-part, vacuum-moulded in ABS plastic, CNC trimmed), impeller pipe, 29 mm impeller, jet efflux nozzle, guide vanes. (all parts injection-moulded plastic), 120 x 6 mm sterin tube with 145 x 4 shaft
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lukehallbland

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Re: Graupner Jet booster 3
« Reply #6 on: July 29, 2009, 02:05:25 PM »

Thank you for the help and reccomended motor, looking at the options for that one would you expect the 12 turns one to work happily or is there a risk of over stressing it. As for amps, am I correct in think that max amps is the amount it can withstand before melting as apposed to how much you would expect it to draw when running at full speed?

Turns    Max Amps    Resistance    RPM/V    I0(A)
6              102            0.0049           4090         5.8
12              51            0.0199           2045         2.2
20              31            0.0554           1220         0.9

Pic of the sub in question just in case I'm being stupid in using it in the first place.

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nick_75au

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Re: Graupner Jet booster 3
« Reply #7 on: August 02, 2009, 06:57:16 AM »

I would go for the 20 turn, it has more torque, and it has a no load RPM of 15000 rpm( as opposed to 24000 rpm and 49000 rpm of the other two motors)  on the 12 volts you intend to run.

You are correct in your assumtion that the motor amps specified is the maximum it will handle but the lower turn motor will also draw more current on the same prop compared to the higher turn count motor.

 Remember that the 1:10 buggy motors are designed for significant gear reduction and nominal 7.2 volt operation hence the high Kvs usually specified. I would almost be inclined to find a lower kv larger frame outrunner (relativity cheap)  or faigao 540 inrunner (expensive)

Nick
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