Help mounting propshaft and motor

hello
im building mobile marines narrowboat and am having a little issue with mounting the propshaf and its motor and was wondering if anyone could help


the problem is that to mount the propshaft parallel to the keel(flat bottom boat) is not possible as there is not enough room for the motor so do i...


mount the whole lot at an angle leaving the prop tilted downward slightly or is there a way of mounting the motor out of line with the propshaft using a coupling?

I'm not familiar with that model, but the usual solution in these circumstances is to mount the motor above the shaft and link them using pulleys and belts or toothed belts.

Barrie

It will be a problem if the shaft is parallel and so low because you will always get water ingress up the tube.

The other problem you'll have is getting the motor low enough to line up the motor shaft in a straight line.  The small angle of the propeller is quite normal and does not affect the running of the boat.  I usually set the inboard end of the shaft above the waterline and the motor in parallel with it.

Hope this helps, 

ken

so slight angle it is then,cheers!

i did look at some motor/gearbox systems were the motor is offset but these are for hi rpm powerboats...not scale speed

if you use a double coupling with a splined joining piece between the two, you can eliminate much of the angle  between the motor and the shaft
 and thereby remove a lot of the resistance.........have had to do it in the past with my lifeboats and it works, giving longer running times. but also Kenny's and Barrie's solutions are also viable.......it is your choice in the end.

by the way.........welcome to the site, and glad to see you posting. cheers, neil.

blue danube wrote:

so slight angle it is then,cheers!

i did look at some motor/gearbox systems were the motor is offset but these are for hi rpm powerboats...not scale speed

Its actually very common to use these systems for scale boats to reduce the revs and increase the torque available. Many tugs used for tug towing use geared motors, but angling the motor is a viable option.

Barrie

I actually built those models and had the same issue. 
My resolve was not the norm...

i'll try and dig u photos for u later tonight if i can find them... but for now this is how i archived getting that motor in place...


first up i slit the hull on the keel with my dremel and dry fitted the motor so it was level with the shaft. i had a internal slot in the keel and a slight hole either side in the base of the hull... but the motor fitted!

next i added some strip wood either side of the motor this keeps the motor from moving left and right.. 

Then i wrapped the motor in cling film , mixed up a load of P38 and filled between the strip wood sections inside the hull, then pushed the motor into the p38. not only dose this make a PERFECT mold of the motor but also filled the hols in the underside of the hull.

once the p38 was dry i pulled the motor out and sanded the under side of the hull where the p38 ha squeezed out.. you will find that the hull in that section is n longer perfectly flat.. however its an acceptable slight bulge along the keel, which no ones going to see anyway.

after sanding I fitted the motor back in place. then with a piece of brass i folded over the top of the motor with a bit of rubber strip under it to grip the motor and screwed it into the strip wood either side.


I promise i till dig up a photo and you'll see what a neat job it is.

like the idea of a gearbox now,just looking at whats avalible

http://www.westbourne-model.co.uk/acatalog/Robbe-Electric-Motors-For-Model-Boats.html

Navy Powerset 600/24
Robbe Compact 3.3:1 Pt No 4105
cant find specs for any of these two though(shaft dia etc)

Well you can always look at MFA geared motors with the spindle which is lower ( i tend to use these for all my larger models thowing big props) around £10 normally. you'll want a 2.5:1 gear ratio 

but if you opt for the T4 motor fitted inside the hull with a perfectly aligned shaft like i did then these are the photos on how i achieved it.

nice fix! not ready to cut into my hull just yet,see what other solution i can come up with first

Blue Danube

Take a look at HPC Gears www.hpcgears.com 

They sell sprockets and toothed belts with calculators for calculating the correct belt length.  These will be quieter than a gearbox, and gives more freedom in mounting position for the motor, and the reduction ratio

Barrie

That wasn't my preferred solution, but i didn't want to swap out a T4 for a geared motor ( T4's are just epic) so my only other option was a misaligned double UV joint which i really dislike doing, no offence to anyone who dose but thats just to much messing around and given you don't have much room in the hull length wise due to the bulkheads then it wasn't really a option either.
this method i used looks a bit nasty, but i can assure you that the keel is almost perfectly square right to the inside corner to the hulls flat and the ''green'' is the slightly bulged area, which now painted you can't even tell exists and anyone who may see it would only think its a moulding deformity.

Its never leaked and infarct i've found being that close to the water has kept the motor cool, i found T4's do get quite warm when running 50mm props and this ones the motors bone cold after a decent run.

As i said not my preferred solution but one that worked in this instance.

http://deansmarine.co.uk/shop/product_info.php/cPath/5_16/products_id/281

deans do a small gearbox too

if u go down the geared motor route then heres a link to several with the spindles that are very low allowing for better mounting and alignment. 

http://www.cornwallmodelboats.co.uk/acatalog/mfa919d.html

i'm currently about to use one in the springer i'm building with a 6:1 gear ratio but this time im throwing a 50mm 4 bladed prop not a 50mm 3 blade with a low pitch.



Another model i've used theses on was my Marlene shouel buster tug, which had an even worse option for mounting and i ended up flipping the mounting bracket of the motor upside down and floating the motors  on pillars!

i think ill give one of these a go! lots of other applications for it if it dosent work out