Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[Glyn Roberts]

I am building the Dumas Dauntless and it will have twin CEM 900's.   I would like to power them with 24V and although I have googled and looked at loads of postings I cannot find how to achieve  this.  As my knowledge of batteries stops at lead acid I need info to make this happen.   I am not to keen on Lipo and would prefer Ni-MH if possible.

Regards and thanks Glyn.

[dougal99]

You will need to wire 2 12v batteries in series to get 24volts.


Look here for NIMHS 


http://www.componentshop.co.uk/batteries/airsoft/108v-12v-packs

[malcolmfrary]

If these are the motors, - http://www.cornwallmodelboats.co.uk/acatalog/cem900.html - I would not run them on 24 volts.

[inertia]

I think those motors are too big and too slow, even if you could get away with running them on 24v (I agree with Malcolm about that). If you're wary of going brushless then I'd suggest two of these on 12 volts with 40-45mm props. http://www.componentshop.co.uk/775-dc-motor-12000rpm-with-mounting-bracket.html
O - and don't use SLA batteries, for all sorts of reasons.
DM

[jarvo]

Try having a look at the T12 or T24 from MMB, i have 1 T24 in my Amsterdam with a 90mm prop, very over speed but superb power for towing. Electronize ESC


Mark

[inertia]

Mark
Check out the Dumas Dauntless. It isn't a tug.
It's a 1940's twin-engined "Commuter boat" i.e. a fast motor yacht. http://www.cornwallmodelboats.co.uk/acatalog/dumas-1211.html
This one has two 700BB Graupner motors https://www.youtube.com/watch?v=xim53MEv4Ew
CMB suggest 2 x Robbe 700/13 motors. http://www.cornwallmodelboats.co.uk/acatalog/Robbe-Motors.html#aR4470
The CompShop 775's are similar to the Robbe ones but cheaper.
Two 35mm brushless would perhaps be best if you want insane speed. https://www.youtube.com/watch?feature=player_embedded&v=G1nhXyvxxLk   


Dave M

[Glyn Roberts]

Thanks to everyone for Their input.

I have now discovered that due to my purchasing the dauntless running gear, I must have  3/16 dog drive props.    The smallest props, (one RH and one LH)  available is Dumas 2 inch 3 blade.   As these are somewhat bigger than the 40-45mm props that  DM suggested I am once again looking for the right moters.    The top speed of the original Dauntless was 50 knots and I would like to achieve scale speed with some extra in hand.

The running gear for the Dauntless was in excess of £100 so I guess I am stuck with that setup.

Regards and thanks Glyn

[Glyn Roberts]

I am sorry I wasted peoples time answering my query only to find that this is a new ball game because of the prop size.    Would anyone like to point me in the right direction with motor type, size, taking into account my previous post.   

Regards and thanks Glyn.

[jarvo]

HI Glyn


Not wasted mate, experience!!!!! try prop shop for your dog drive props, or dave marles who does all the racing type gear


Mark

[Glyn Roberts]

Hi Inertia,

Could the motor that you suggested ( http://www.componentshop.co.uk/775-dc-motor-12000rpm-with-mounting-bracket.html)  handle 2inch 3 blade props that dumas supply?  It has the revs but does it have the torque.  He only has one in stock at present.   I appreciate the help you gave, thanks.

Jarvo

Prop shop do not do a pair of counter rotating props in the required size.  I am still looking at dave Marles most of them are racing props so far.

Thanks for the Links.  Regards Glyn       ( PS Does not appear to stock 3/16 dog drive props.)

[jarvo]

Hi Glyn


Try Deans Marine Ron stocks hundreds of props, give them a ring and see what they suggest


Mark

[inertia]

Could the motor that you suggested handle 2inch 3 blade props that dumas supply?

It's borderline. I don't think that the published data on the 12,000RPM 775 is correct (it's the same for both versions) but I wouldn't fit anything larger than 45mm 3 blade props. What are the motors that Dumas recommend (apart from eye-wateringly expensive and/or unobtainable)?
I think you're gradually drifting towards brushless motors here, Glyn. There's no need to be frightened of them!
DM

[Shipmate60]

A geared 2.5:1 550 brushed motor will power her on 12 volts.


Bob

[Glyn Roberts]

Thanks Inertia,

The Dumas motors are the 2004 6Volt or the 2005 12Volt,  for high speed the Astro 25.   All at heart stopping prices.

I think that you are right that I should go for brushless but I know very little about them.    As I am commited to the running gear and have ordered the 2inch props is there a brushless motor that would fit the bill and work with that setup?

Regards Glyn

[inertia]

Glyn
I've sent you a PM
Dave M

[sparkey]

  I would go for 500kv outrunners will give plenty of torque and easily handle those props with power to spare and will need a 60amp ESC, these can be obtained from HK or flea bay for very little money,Ray.

[Glyn Roberts]

Hi Sparkey,

thanks for info, good to know that there are answers to this question.     

Regards Glyn

[sparkey]

  I forgot to tell you go for car ESC's and you don't have to worry about water cooling and outrunners don't need it anyway,Ray.