Joffre motor advice please

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22 October 2014 at 16:41 #52925
Terry Plumridge
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@terryplumridge66794
Motor recommendations for the Caldercraft Joffre tug please. It is 775 mm long, has a 40mm dia. prop, and I want to run it on 6 volts. I am thinking of an MFA gearmotor which will give 3000 rpm at 6 volts, but are they very noisey? Any other ideas welcome.

Cheers, Terry.
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22 October 2014 at 16:41 #5334
Terry Plumridge
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@terryplumridge66794
22 October 2014 at 19:07 #52932
ashley needham
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@ashleyneedham69188
Terry, an MFA 540/1 motor (the low power one) will spin this ok, I was going to suggest that old faithful a 555, but this may be a bit slow on 6V.

3000rpm mind you is not very much for a 40mm prop, I would not go to gear drive for prop that small personally.

Ashley
22 October 2014 at 20:02 #52934
Banjoman
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@banjoman
When I started building my Mountfleet Models "Highlander", which is 838 mm long, ballasted weighs in at some 12 or 13 kilos total weight and has a 60 mm prop (I think it was 60, but close to that anyway), I was recommended by one of the better known marine modelling online shops to use an Electronize EL545/12 (also, it seems, sometimes referred to as EL543/12), see **LINK**, which thus is what I've put in

So far I have only tried it out in the local testing dock (aka the baththub), and there at least it seems to provide both the comparatively low revs and high torque needed. I dare not yet swear by it, though, as it does of course remain to be seen what it will do on the pond over a full sailing run when I finally reach that stage (maybe next spring or something like that).

/Mattias

Edited By Banjoman on 22/10/2014 20:03:15
22 October 2014 at 22:22 #52938
Mark Jarvis 2
Participant
@markjarvis2
HI Terry

40mm prop sounds small to me, are you sure of size?? the electronize motor would suit you for the revs 4500 but that is off load, not in the water.

You will have a heavy tug when finished, a small motor and prop, you may not have the control you would hope for.

Is there a reason for choosing a 6volt system?? 12 volts with a car heater motor and 7ah battery would give you the power and a descent running time, the battery would give you some much needed ballast.

Mark
23 October 2014 at 10:07 #52952
Terry Plumridge
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@terryplumridge66794
Hi Mark, 40mm prop is included in the kit. 6 volt because I already have one, but 12 is not out of the question.

Thanks, Terry
23 October 2014 at 12:10 #52953
Mark Jarvis 2
Participant
@markjarvis2
HI Terry

If i remember right the prop is cast in white metal, have a look at the plans, i would think that there is size to fit a larger prop say 55mm and brass or cast in better metal, would give much better thrust and control.

With one 6 volt battery a second gives you more ballast weight!!!! caution, make it removable your Jofree will be about 20 kilos fully loaded,

Regards

Mark
23 October 2014 at 18:06 #52968
Colin Bishop
Moderator
@colinbishop34627
I don't like the white metal props that many manufacturers offer. Much better to substitute a nice efficient brass one which will be better balanced and weigh less.

Colin
25 October 2014 at 21:35 #53050
Mark Jarvis 2
Participant
@markjarvis2
Hi Colin

They also look better, on the bench or at the side of the pool. joe public notice things like that

Mark
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