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[davejay]

Hi all,


I've had to change tack on projects slightly and I'm now embarking on a 59" Narrow boat build based on the excellent Orion Mouldings GRP hull.


Problem is I had squirelled away some parts for the initial planned build of a different project. So now I have a MFA 800 brushed motor and a MTroniks 30a tio speed controller and two 12v 7ah sla batteries (great for ballast weight)


My issue is that the MFA sits a tad high to line up with the centre point of the propshaft exit, I could bolt it directly to the hull and resin it in place but I'm a bit concerned of putting strain on the grp (although it's quite thick and flat). I could use a geared motor which would allow me to raise the motor up on a ply plate and resin that in place but need to make sure that a geared motor is man enough to propel a quite weight narrowboat!


Got myself a bit confused dot com!!!


Any advice would be great.


I don't really want to spend dosh on more motors/batteries/speed controllers!!!


All the best,


Dave

[Baldrick]

  I would go for the geared motor which will allow you build up a solid base for the motor and get the whole on a true line and level through the motor coupling and shaft .
  Not going for the canal scale speed record are you ?
I would have thought that a geared motor would have put less strain on the transmission than without, the MFA gearboxes are pretty sturdy affairs

[davejay]

  I would go for the geared motor which will allow you build up a solid base for the motor and get the whole on a true line and level through the motor coupling and shaft .
  Not going for the canal scale speed record are you ?
I would have thought that a geared motor would have put less strain on the transmission than without, the MFA gearboxes are pretty sturdy affairs

Thanks 'Baldrick '


Not going for canal speed record but don't want it to be under powered.
I was looking at using a smaller motor but worried about it definitely being underpowered!


Any ideas??


I'm finding it a bit tricky finding a belt drive gearbox for the mfa 800. I was looking at the graupner 700bb motors. So much confusion!!!

[davejay]

In thinking also that there wouldn't be much difference in epoxying the motor mount directly to the hull as it's totally flat and would have a maximum surface area of adhesion, backed up by 4mm bolts with nylocs threaded through from the hull exterior with washers to spread the load from the bolt head (being underneath it's not visible)


I was also thinking that if I use a longish propshaft i could angle this down ever so slightly (I'm talking millimetres here!).......there's plenty of room in the hull!!




I know, it seems like I'm answering my own questions, just wandering if anyone can confirm my thoughts!!!


Cheers,


Dave

[J.beazley]

Double huco couplings direct drive and raise the motor slightly on a ply platform


Jay

[davejay]

Double huco couplings direct drive and raise the motor slightly on a ply platform


Jay

Thanks Jay,


I was thinking of using a double huco set up to allow for a slight drop in angle.


Do you think that the MFA direct drive is a bit too torquey? ( it was originally intended to go in a Mountfleet osprey!)


Looking at the geared MFA 500 but not sure which gearing to go for....2.5:1 or 6:1 or...............  God knows!!!

[Baldrick]

Dave.


     I think my overriding concern would be noise and vibration , you have a fibreglass 5ft long trough 7"x7" and you need to prevent it developing harmonic vibrations to which end keep your prop shaft as short as possible, drop the shaft speed by gearing down keep the driveline absolutely straight build in lateral stiffeners and a solid base for the motor mount.


cheers Balders

[davejay]

Dave.


     I think my overriding concern would be noise and vibration , you have a fibreglass 5ft long trough 7"x7" and you need to prevent it developing harmonic vibrations to which end keep your prop shaft as short as possible, drop the shaft speed by gearing down keep the driveline absolutely straight build in lateral stiffeners and a solid base for the motor mount.


cheers Balders

Thanks Balders.


I did have a concern about noise and vibration, my initial thought was to place a small silicone o ring at each fixing point, I have now decided to run lengthwise 'beams' and cross members and mount the motor to those with silicone o rings in place to negate as much vibration as possible and with a copious amount of resin to bond it all in place. I have also gone for a 5" propshaft ( with oiler) and a double 'Huco' coupling to take out the small amounts of misalignment. Obviously I will try and get the alignment as straight as possible in the first instance.


Next thing I need to think about is the rudder.......   but one headache at a time though!!!




Thanks for your advice Balders, helped me head in the right direction and saved me some head scratching!!!


All the breast,


Dave😊

[Tug Fanatic]

Gearboxes are inherently noisy. If you want a reduction gear then timing belt drive is much quieter.

[J.beazley]

Thanks Jay,


I was thinking of using a double huco set up to allow for a slight drop in angle.


Do you think that the MFA direct drive is a bit too torquey? ( it was originally intended to go in a Mountfleet osprey!)


Looking at the geared MFA 500 but not sure which gearing to go for....2.5:1 or 6:1 or...............  God knows!!!

I have a mountfleet OPV the hull is very thin, shafts are virtually flat in the hull with double couplings to a pair of mfa800 motors direct drive, as Tug fanatic says gearboxes are noisy before the OPV had the 800 motors it had a pair of mfa500 2.5:1 gearboxes and they made everything resonate.
If your speed controller has soft start or you get the driveline as straight and free running as you can the motor (800) shouldnt give you any issues at all.


Jay

[davejay]

Thanks Jay,


I've gone for a mix of suggestions!


1) Short as possible shaft to reduce noise/vibration


2) Built up motor mount with silicone o rings to soften the contact between metal mount and base.


3) Double Huco couplings


4) Lots of praying!!


and resin!!!!😁

[davejay]

Gearboxes are inherently noisy. If you want a reduction gear then timing belt drive is much quieter.

I think the MFA 800 isn't that torquey when it comes to it, I have a feeling it will be running at virtually half revs most of the time......If that!!!!!!


I don't have a liking for geared motors, too meccano ish!!!


If I had to go geared then yes I would agree that timing belt is much better!

[john44]

Hi Dave, when I built mine, Also on the Orion hull I used a combo drill single ratio
919 series 4.5>15v. Geared motor.
I glued 1/2” block under the motor mount position with stixall and then screwed the fixing to the block.
That gave perfect prop tube position.
I also fitted a bow thruster.
I use mine on 12v lead acid and 7.2 for the bow thruster.
It will go faster than scale speed if needed to get out of the few idiots in our club.
The bow thruster also works very well. I did however make an oversized rudder.
I am very pleased with Performance of the boat.
I made the ballast removable for easier carrying.
I also glued 3 strips of 10 x 5mm wood under the hull to protect it from rough uneven ground
when on the jetty.


Hope this helped


John