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[Peter Fitness]

I have used both the direct drive and reduction drive methods in my models, and tend to prefer the latter, as illustrated in the photo. What do other members prefer, and why? Does direct drive create a heavier load on the motor, thereby causing a greater drain on the battery? It has been my experience that direct drive generally gives a higher speed, but that is not always appropriate for certain types of model, and it seems to me that the motor becomes much warmer using this method, which may indicate a higher current drain. On the other hand, motors coupled using a reduction drive usually seem to run cooler, which would appear to indicate a lower current drain - what do the electrical wizards think?

The photo is of my version of a pusher tug, which is used as a recovery vessel at our club's lake. The red tubing on each side carries the receiver aerial.

I am currently building a Billing Nordkap kit, and there may not be enough room for a reduction drive, so a direct motor / prop shaft coupling may be necessary.

I would appreciate any comments on this subject.

Peter.

[Shipmate60]

Peter,
A reduction gearbox allows the motor to run faster, but with reduced load.
This allows the motor to run more efficiently transmitting loads.
This in turn effectively reduces the power required to turn the prop under load so reduces the current consumption.
The downside is you get a reduced rpm at the prop so you might be able to use a smaller motor on direct drive.
For larger slow running props it is usually easier to fit a 3 or 6:1 gearbox instead of a far bigger motor running much slower.
I have several 550 motors on a 3:1 gearbox which will only pull about 2 amps, direct drive they would pull 6 plus amps but you do lose just over 2/3 of the revs.

Bob

[Martin13]

Peter,

Are those the John Darke motors? What cells and voltage are you running ???

Martin doon under

[Subculture]

I tend to favour direct drive. Unfortunately it can be difficult to find suitable marine motors at you local model shop- most are geared (no pun intended) towards car and aeroplane use, and usually too high revving and low in torque- thus necessitating some form of reduction to convert the revs into useful torque.

Exceptions to this are some of the motors in the Graupner range, like the 720BB, 900 and 500E. All low(ish) revving motors suitable for direct drive- the latter motor is okay for smaller models.

I also look at ex industrial motors like Buehlers, Maxon, Pittman, also motors from electric golf caddys, car blowers etc. These are usually far better quality motors than you'll find in a local hobby store and can be picked up quite cheaply if purchased surplus or secondhand. The main snag is that the motor data isn't always readily available, so there is an element of chance. however I have found that most of the companies are helpful with motor data if you email them with a model number.

Andy

[Bryan Young]

I tend to go with direct drive. I originally fitted "Bluebird of Chelsea" with 2 geared motors. I found gearboxes (at least the ones I had) to be too noisy. Also, although the cruising speed was OK I did not have enough "oomph" to get out of the way of the suicide / blind brigade. Although still on 6 volts, I can now "escape" in silence.

[Peter Fitness]

Thanks for your input everyone.

Martin, yes they are John Darke motors, which I purchased from him on one of his visits to our lake. I'm using a 6v 10ah SLA battery to power them.

Andy, the fact that many model motors are high revving is the reason I normally use a reduction drive.

Bryan, I use a belt and pulley reduction, as shown in the photo, which is extremely quiet. I turn the pulleys up on my lathe, and use a home made adjustable mount to tension the belts. Some of the geared reduction drives are indeed noisy, and I have also found some direct drive couplings to be rather noisy too, I suppose it depends on the quality of the coupling.

Peter.

[HS93 (RIP)]

this method may enable you to still use a belt drive I have made lots for people and there does not seem to be problems with this way of doing it and you can use just round belts but i tend to use toothed as they can be run slacker and don't slip and because they run slacker you don't put as much strain on the end bearing of the motor. picture marked adapter just use a flat ally plate and the oiler is on the side but could be behind motor. the handy thing is that you can make it and drop in as one unit no lining up the other two pictures use a turned thicker heatsink plate.

[hopeitfloats]

thats a very neat set up. where do you get your belts/pulleys from though.   

                                                            craig

[HS93 (RIP)]

I tend to use http://www.hpcgears.com/  but I am in the uk, they will export. they have a nice calculator for belt length on there site. the adapter can be made from tube and a brass washer solderd on.

Hs 93

[hopeitfloats]

thanks Hs.  i will dash off and have a look at that site now

[HS93 (RIP)]

http://www.sdp-si.com/   also 

 http://www.canningsgear.com/page11.html#Anchor-ENGINEERING-48213   

 http://www.technobots.co.uk/

Also a lot of 1/10 buggies and touring cars have them that can be adapted , have a word with your model shop that sells them

Hs93

[hopeitfloats]

  more options. that technobots site i have been on but couldnt remember the name. unfortunately there arent many model boat suppliers in nz and the shops that do have parts only tend to have a small selection so buying outside of nz isnt that unusual for me. thanks again Hs.

                                 craig

[HS93 (RIP)]

Craig have a look at this Company they sell synchronous timing belts..worth a try


http://www.beltdrive.co.nz/index.html

Peter Hs93

[barriew]

I am currently building a Billing Nordkap kit, and there may not be enough room for a reduction drive, so a direct motor / prop shaft coupling may be necessary.

I would appreciate any comments on this subject.

Peter.

Peter, My Nordkap is a Direct Drive with - I think - a 385 motor. For me that gives a slightly over scale speed on 6 volts at full throttle. There's not a lot of room inside, so I don't think you could get more than a 6v 1.3ah battery in there.

Barrie