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Electric motors - where?

R/C Submarine modelers

Postby Wayne Frey » Fri Feb 20, 2004 11:57 pm

Where can I find the pittman-dumas electric motors larger than the "500" style?
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Postby Wayne Frey » Sat Feb 21, 2004 8:02 pm

Tp be a little more exact--. I am looking for a "900" size motor. I checked hobbie lobby,but 700 is as high as it goes there.
Pittman makes the Dumas motors, I think.But have not been lucky finding them online.
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Postby Wayne Frey » Sat Feb 21, 2004 11:37 pm

A 700 can work after all.
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Postby kd6hq » Sun Feb 22, 2004 4:25 am

Wayne

If your still looking try Harbor Models.
Don

Keep the faith.....
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Postby Dolphin » Sun Feb 22, 2004 4:34 pm

Comrade Wayne! (referring to your passon for Russian subs)

Perhaps your referring to the Graupner 900 BB torque? Awesome powerful motor. Very efficient for it's size and cost (71%). About 45-50 American dollars. Unavailable in the USA, but available (very common) in European hobby shops. Likely unavailable in America because model boats here take second to model cars and aircraft....why would you need such a large motor in a mere R/C car? We in this hobby need to change this by making a bigger 'splash' you might say!

This Graupner 900 BB torque would be used direct drive and turn a prop around the same diameter as the motor casing. This is the common rule of thumb way European (mainly German-Dutch and other) submarine modelers set up their boats. Characterized by direct drive/most efficient vs. cost/and unity in size of motor casing = propeller size. In the United States we use smaller motors Graupner 300 to 700...reduction gear/belt drives. We tend to build with enough propulsion power to drive us to the surface. German modelers tend to use enough propulsion power to reach the surface and beyond! LOL! These motors work best using large Ni Cad batteries....this is where you will pay the money....200 plus dollars? However these batteries though not cheap when soldered into a large battery....will allow shorter time recharges and many more recharges....in the hundreds....vs. many dozens of recharges using acid lead gel cells. Conversely....Gelcells are water proof and a order of magnitude cheaper. In Europe they operate their propulsion motors around 12 to 24 volts. We in America generally tend to set our propulsion systems up 6 to 12 volts. These Graupner motors (and Maxon if you can find used ones cheaply....these motors are ...as my boss used to say....godlike!) run more efficiently on higher voltages. I think good power without the incredible speeds...with good endurance is best....balancing endurance and speed...I would lean toward more endurance....at least as long as your transmitter battery that is.

Contact European hobby shops for these large motors if you think you would want to use one. These Graupner 900 bb torque..(the BB is for ball bearings) are also well liked for their very extremely low and very smooth RPM's without stalling. I have two of these motors..one in a model ...and a spare....but you can't have the spare though either! Spare to be used as a spare..and for a possible future 'dream boat'. LOL. Consider if these are for your Bars (Akula) and Alfa class models consider going with 700 size Graupner series motors direct drive? Direct drive is simpler and the 700's are generally more efficient still...(around 75%). Just in the water apply power to the prop very slowly from a standing start........like a beautiful sounding Merlin engine on a P-51 Mustang.....otherwise the torque will rule you and you will be trying to take off from the taxiway and not the runway.....water wise I mean! These greater speeds (frightening really) will also have a great bearing on your automatic pitch or angle sensor controls....so adjust and harmonize these with the manufacturer of the APC accordingly. This also implies a big pond too to fly around the galaxy. 'Engage!'

http://homepage.ntlworld.com/edward.....ner.htm

Steve Reichmuth
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Postby Wayne Frey » Mon Feb 23, 2004 1:22 am

Of course I am thinking of the drive for the 1/72 Akula. Origionally, I had guessed (only guessing) a 700 motor with a 3 to 1 drive. Then the 900 was suggested. Then David Merrimen suggested a 700 motor with a 9 to 1 reduction.
Being a less common hull (not many 1/72 Akulas out there YET) the answers are not readily laid out like they are for,say the 1/72 Alfa that everyone knows.
For present, I will probably go with the 9 to 1 700 motor. Sounds interesting. I certainly do not want to underpower that hull. And a few bucks one way or another will not stop me from picking the best motor for it. Nine to one reduction sounds interesting. I know Merrimen is right, but this is a good place to start a stringer about applications of various reduction unit ratios for (In my case a larger boat), different things, and when to go with what size motor.
I do not want the boat to launch like a mark 48 when I touch the throttle. To choose wisely will give a better rounded boat. With enough power to give chase to any other ship without wanting for speed,yet has low speed pull.
Thoughts?
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Postby Dolphin » Mon Feb 23, 2004 2:26 am

Go for a well rounded boat Wayne. All speed is not everything...the Alfa's were sexy and fast...but do you see many in commission still? 3 to 1 with a 700 Graupner is plenty. 9 to 1? Your building a pump jet version of an Akula! Your leaping in quickly.

No official 'public' announcement about such a Akula PJ version, but it has been rumored. 5 to 6 years ago it was claimed a Russian SSN was tracked in the North Sea, first by Sweden, then Norway, then the British Navy. The story goes the Russian skipper might have been showing off a little....making noise.....then suddenly going quiet. Then becoming noisy again. The same sub....appeared a known time and distance from it's first point where it went silent. A little math. The distance traveled silent could only been accomplished at a 'faster silent speed' that we understand a PJ provides ...as we understand PJ's. Hence the showing off. Just a rumor. If true....what would it look like? Likely robust as the Russians like them robust. The UK, USA, France use them. Would seem odd the Russian designers would not 'dab' at them too. Likely the newest Russian SSBN design would employ one. These Bars (Akula) submarines were built by the Amur Shipbuilding Plant Joint Stock Company at Komsomolsk-on-Amur and at the Severodvinsk shipbuilding yard. Seven Akula I submarines were commissioned between 1986 and 1992, and three Improved Akula between 1992 and 1995. Three Akula II submarines, with hull length extended by 4m and advanced machinery quietening technology, have been built. The first, Viper, was commissioned in 1995, the second, Nerpa, in December 2000 and the third, Gepard, in August 2001. Notice the lag time of 4 years between the commissioning of the second and third vessels in the improved group. A lot of this delay was most certainly due to the severe financial difficulties the Russian Republic had during that time period. Gepard was delayed because the Severodvinsk shipbuilding yard workers reportedly had not been payed for many months! I am sure the workers and designers were not idle during this time. 'Quietening technology' means much more than just a PJ in submarine design. The rumored report and the lag time between the second and third improved Akula makes me wonder if....assuming they do in fact have a pump jet on one or more of these SSN's, could it be either the 'Viper' or the 'Nerpa'? We need facts if possible, otherwise I am just writing wind! The Akula III (was it Gepard?) was shown conspicuously out in the yard and out of the water while labor problems at the Severodvinsk shipbuilding yard were resolved. It showed a beautiful 7 blade propeller. Was this also a convenient way to present a different impression to observers? We are really out there.....next stop alien autopsy photos? We need more 'stuff'.

Go for it Wayne! :)


Stevie 'wonder' Reichmuth
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Postby Wayne Frey » Mon Feb 23, 2004 7:35 am

I have pictures of the "Vepr" showing beyond all doubt it too has the prop, not a pumpjet. The "Kugar" has been quite hard to find information on.
Does not matter, I have pictures of a russian pumpjet and will adapt to my hull. If I cannot prove the Akula pumpjet, I will build one anyway. Be a killer "what if" boat.
As for the reduction setup, it is interesting to see which way to go. May have to experiment mechanically after it is built, but good logic and math applied here will probably hold true on the finished product. Is there a formula for determining ideal thrust,ratios,draw,etc?
As for information on russian boats, I may be announcing some really cool news in the near future as I have dug up more stuff.
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