The Ship Model Forum

I need to find to 2 PM motors for my 84" CAG-1 4 screws. In the past I adapted various 12VDC automotive motors such as power window and wiper motors. In most cases they were a bit of an overkill. I'll also need a varistor for speed control. I want to stay with the old-school PM -permanent magnet- types, whereas they offer better low speed performance. Any suggestions?
thanks

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What size props?

4 @ 1.5"

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We use this guys Ford Buhlers in many of our club models. Just send him, Sebastien, a message and he'll get back to you. He is in Canada. Some tst resultsa to give you an idea of the performance attached.

I PMed him and he and no idea why you thought i should have contacted him. Do you have an email addy? Also I fond the below brushed DC motor that seems to be close to the one at the top of your chart. What are your thoughts on using 4 of these motors for my 84" CAG? Specs below:

Banebots RS-555 12V 7750 RPM Brushed DC Motor

• Operating v: 5v - 15v
• Nominal v: 12v
• No Load RPM: 7750
• No Load A: 0.4A
• Stall Torque: 29.16 oz-in 205.9 mN-m
• Stall Current: 15A
• Kt: 1.94 oz-in/A 13.7 mN-m/A
• Kv: 646 rpm/V
• Efficiency: 68.5%
• RPM - Peak Eff: 6660
• Torque - Peak Eff: 4.76 oz-in, 33.6 mN-m
• Current - Peak Eff: 2.5A
• Mounting Screws (2) M3

Size:
• Weight: 7.5 oz (213g)
• Length for motor: 2.24 in (57mm)
• Diameter (with flux ring): 1.5 in (38mm)
• Diameter (no flux ring): 1.41 in (35.8mm)
• Shaft Diameter: 0.13 in (3.2mm)
• Shaft Length : 0.3 in (7.6mm)
At $6.25 I don't need to worry about replacing brushes, I'll just order a extra motors.

So, will they suffice?
Thanks

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Odd, he doesn't seem to be active now. We lat bought 12 months ago from him anf have been buying since 2008 from him.


They should work, we did use some 555s but they ran hot and used more amps than the Buhlers. A 5 pole motor versus a 10 pole motor. The other problem we hit was when we bought a second batch and they gave completey different results to the first batch.

Thanks, I'll give them a try and put a fan blades on the output shafts before the shafts for the screws.

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You could do or put an aluminium plate across each pair of motors with a computer fan on top like these.

http://www.ebay.com.au/itm/Red-11-Blade ... 5d4d3d7e1c


eBay has plenty of these.

Hi CAG-1NUT

The prop pitch will have a dramatic effect too. Scale/ course pitched props are fine for live steam (low revs high torque) but you will need shallower pitched props for electric power, or connect them to the shaft via toothed belt reduction. This might explain the excessive heat from the motors.
The Mabuchi web site is good and it gives load/revs output for their motors. This is very handy if you come across a motor and want to find out what it is best used for, just punch in the Mabuchi ref off the back of the motor.

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PICKETBOAT

www.chyldshallmodelshipyard.com

Sorry to disagree but a scale model to me should have scale props. Warship props of the WW2 era were like the attached photo of George Sitek’s props one of which was used for testing. We have many models in our club and just about all run direct drive. These models can run props up to 78mm plus in size only drawing 3.95 amps in the water when coupled to a decent multi pole motor. Multipole as in 10, 12 poles etc. BTW, by hot, I meant that after 10 minutes of running, the motor was too hot to touch. The Buhlers get warm like all motors do but not to the extent of the Mabuchi’s. I do use some 555s but not with warship style props.

From what he said, Inuit is building a 1/96th scale Baltimore which would be 84.2” long and displace about 44lbs. A 1/72 scale Leander Class cruiser which uses these motors is 92.5” long and displaces about 58lbs. It needs power to get moving and more importnatly, power to stop in a hurry when the inevitable happens and some just turns across your bows.

I have run 2 in a 1/72 scale Leander Frigate for about 15 years now. She wears 50mm 5 blade scale petal props and with the Buhlers is pulling 4.8 amps flat out. With the 555s, she was pulling 6 amps. At 12 volts, that is about 22% more watts (heat!) than the Buhlers. She does run the computer fan cooling system I suggested partly as there is virtually no airflow possible in the long thin hull but mainly because the outside temperature can regularly be in the high 20s C and up to 37 C (100 in degrees F). At 28 degrees, I’ve checked the temperature in her just sitting at her mooring buoy and she has recorded 42 degrees inside. The esc also runs that system to keep it from tripping the thermal cut out built into them.

Thanks for the info guys. I have much to think about. I will be making 4 screws like the one in the photo and I'm now leaning toward using 2 larger motors one for each side and employ pulleys and belts -basically O rings- such will make it easy to change the ratios.
BTW I'm making good progress on the ship. The hull buck -which will also be a model is about 85% done. I've also started on the superstructure. Photos soon.

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