Hello Andy,

I have no experience of narrow boats but I believe that they are relatively slow. The Graupner 400 does about 16,000 rpm on no load at 7.2 volts. I suspect that you need to look for a lower revving motor or use gearing/toothed belt to reduce the rpm. On your behalf I'll ask the forum – "What is a good propulsion setup for a 1 metre long narrow boat ?"

Ian

Hi Andy,

I think the answer to your question is yes you could use that combination, but it would not work very well. There are several Graupner 400 sized motors and they all do over 16000 rpm on no load at 7.2 volts. In reality with a 30 mm propeller immersed in the water the rpm they could achieve would be much lower, well away from the optimum speed with the result that the motor would get pretty hot. You could fit a gearbox or belt drive with something like a 4:1 speed reduction but they tend to be noisy and you would lose some power and efficiency and might not have the space to do it.

My narrow boat is 1.06 metres long and weighs 8.3 kg. It has a Graupner Speed 500E motor (part number 1788) running on a 7.2 volt battery, driving a 40 mm 3 bladed propeller. Performance on the water is very realistic and if you do use full throttle it can manage greater than scale speed, although it takes a while to accelerate. The free running speed of this motor is 7200 rpm and with the prop in the water it achieves about 3000 rpm. I have tried the same motor in another application with a 30 mm prop and it achieved 4700 rpm which is actually a very good match, better than in the narrow boat. That would be my recommendation but there may well be other possible solutions.

One point to be aware of is that motor manufacturers make lots of different motors which may be of similar overall size and designation but can have widely different characteristics. If you want to understand what combinations of motors, propellers and battery voltages work then you must be clear exactly which motor part number you are considering. There was a smilar question on another part of the forum a couple of days ago when someone asked for a motor recommendation for a particular model. Someone recommended 'a Johnson motor' which is virtually meaningless since Johnson make hundreds, if not thousands, of different electric motors.

Gareth

Andy. And this is only a personal view, If 30mm is a good prop size for your canal boat, the personally I would simply use the 400, as you have it already. Remeber it only does 16000 rpm on full throttle and does go slower on part throttle or you could use a 4.8V batt . Depends if you want to buy a second motor or not

30mm is quite small for a prop and at slow revs you are not going to get much oomph, canal boats being unweildly and (possibly) heavy ?? a bit more power in reserve I find is always handy.

If you had a 40mm prop, then of course the situation would be different and as suggested a larger low powered 500 sort would be required.

Ashley

This is a lovely little motor http://www.mfacomodrills.com/motors/385ln.html and would be just the job in your narrow boat with a 3 or 4 blade scale prop (30mm) on 7.2v.
If you want a bit of power in reserve then try one of these 555 Mabuchis http://www.action-electronics.co.uk/pdfs/MOTORS02.pdf with a slightly larger prop on 6 or 7.2v.
For a transmitter I would recommend the "instant" type of rechargeable cells like these http://www.component-shop.co.uk/html/aa.html#IN2500AA A four-pack of the Vapex 2100mAH will cost little more than four AA Duracells and a plug-top charger maybe another fiver. I wouldn't use those budget "ten for a quid" batteries in any modelling application. They're OK for TV remotes, travel alarm clocks and torches but not where there's an expensive (and maybe dangerous) model depending on them.

Dave M