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Author Topic: Bulkhead mounted motors and gears  (Read 1324 times)

GG

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Bulkhead mounted motors and gears
« on: September 05, 2019, 04:24:23 PM »

Sometimes modellers can find it to be difficult to accurately install gears between a motor and propeller shaft. This is often because smooth and efficient operation demands the both motor and propeller shafts must be parallel and correctly spaced, not always an easy task when fumbling around inside a hull.


A method I've used several times is to mount the motor and propeller tube squarely onto a suitable bulkhead before adding the bulkhead into the models structure.  With the motor and tube correctly positioned, the tube can be glued to the bulkhead.  When the glue has fully set, the motor, gears and shaft are removed and the bulkhead plus tube added and hull construction continued.


As the propeller shaft will likely be angled downwards in the model, this also angles the bulkhead by the same amount.  This must be allowed for if building from a plan or kit which does not feature such an installation. The angled bulkhead can be an advantage as it usually creates better access to the bolts used to secure the motor. This method also works with pulley drives.


Have used this method successfully since 1992, so it might be worth considering?
Glynn Guest[size=78%] [/size][size=78%] [/size]
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GG

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Re: Bulkhead mounted motors and gears
« Reply #1 on: September 06, 2019, 05:39:45 PM »

Just found a photo that illustrates this method.


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TheLongBuild

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Re: Bulkhead mounted motors and gears
« Reply #2 on: September 07, 2019, 08:10:46 AM »

Like that, may have to do that with some smaller boats just acquired as they need a 2-1 ratio and very little room.

Tug Fanatic

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Re: Bulkhead mounted motors and gears
« Reply #3 on: September 07, 2019, 08:50:37 AM »

I am sure that many if us will remember that Graupner used to sell these motor/gears/shaft/prop units as Multispeed units. If you glue a block to the back of the main panel & drill the propshaft hole through it using a pillar drill to keep it vertical/ parallel your alignment problems are gone.

You can, of course, do exactly the same with pulleys & belts/ O rings/ elastic bands which have the advantages of not being quite as critical as nicely meshed gears and quieter.

Glynn
These basic tutorial posts that you are doing are great stuff. Can they be organized as a resource in the beginners, or other appropriate, section?
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malcolmfrary

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Re: Bulkhead mounted motors and gears
« Reply #4 on: September 07, 2019, 10:26:57 AM »

Going maybe simpler, just mounting the motor to the prop shaft outer sleeve with a spacer between motor and shaft to give the correct belt length could work?  Obviously the weight of the motor means adequate support for the pro shaft end is needed, but the need to support the bulkhead/bracket is removed.  Again obviously, won't work with outrunners.......
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GG

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Re: Bulkhead mounted motors and gears
« Reply #5 on: September 07, 2019, 12:00:10 PM »

Tug Fanatic'
           Yes, I've used the Graupner Multispeed units in a few models with success.  A neat, simple and easy to install item but I suspect they are no longer available.


I've attached a couple of photos of my home-made version.  Just an aluminium plate drilled to accept the motor and prop tube as with the bulkhead mounting method.  The base being bent to match the hull it was to be glued into.  Still going strong in a tug model.


As for placing these posts in a "Beginners Section" in this Forum, a good idea but it's up to Martyn.


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GG

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Re: Bulkhead mounted motors and gears
« Reply #6 on: September 07, 2019, 12:09:53 PM »

malcolmfrary,
          Yes, that would be another way to do it but I'm not sure it would be simpler than a bulkhead that was going to be built into the model anyway.  For people with an aversion to bulkheads, they could use the idea in the previous post.


As for Brushless outrunners, could they not be fixed to the same side as the propshaft gears?  Perhaps not suitable for monstrously powerful motors though?


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malcolmfrary

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Re: Bulkhead mounted motors and gears
« Reply #7 on: September 08, 2019, 08:36:39 AM »

I was just saying that my take was that brushless outrunners would be a problem to mount to the prop shaft with just a packing piece.  Fitting the motors mounting plate to the bulkhead is close to what happens with any type of motor.
Mounting a cased motor to the shaft does ensure that the two shafts are parallel, with the need for a minimum of ability at hitting accurate right angles during building.  As to acual fixing, depending on the size of motor, there is the choice of adhesive or strapping it all together using cable ties or metal straps with a screw, like a Jubilee clips.


Does the motor/shaft bulkhead need to conform to the hull shape to be part of the structure of the hull? It strikes me that the joining plate could have dummy brackets post-fitted to join it to the hull, unless that was in the original post and went by me.
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red181

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Re: Bulkhead mounted motors and gears
« Reply #8 on: September 18, 2019, 09:16:54 AM »

you can also mount the gears and motor side by side for models with less height, bulkhead is a nice idea though, sometimes the simple methods are the best!
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GG

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Re: Bulkhead mounted motors and gears
« Reply #9 on: September 18, 2019, 09:29:15 AM »

Red181,
          Had to mount the motor to one side of the prop shaft gear in the Higgins Hellcat PT boat (MB June 2008) due to insufficient height under the deck, unlike the Elco PTboat (MB Nov 1999) which had more room.  One advantage of "side mounting" the motor was it allowed the battery pack to fit on the opposite side and gave perfect balance in the finished model.


And yes, simple ideas are usually the best, but they can be a pain to figure out!


Glynn Guest
P.S.  Nice motor/gear mounting plate, much better than my bent piece of aluminium sheet!
 
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red181

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Re: Bulkhead mounted motors and gears
« Reply #10 on: September 18, 2019, 09:47:55 AM »


great minds eh! yes the battery went at the side.


Wish I could take the credit for that mount, my old mentor did that, he taught me what to do, so I have done it since. He set that mount up so that if I wanted to go back to direct drive, it was easy to just remove the gear and motor, and the motor then fitted in the centre, quite clever!


With the advent of brushless becoming more affordable and easier to understand a few years back, the heavy brushed motor was dumped in favour of an outrunner, and with the considerable weight saving of lipos, the need for the gearbox in that 3 foot aerokits fireboat was removed.



When I get round to it, Im going to refit the mount and gearbox, only because its so nice :-))


As you can see, we where testing when this pic was taken, the stuff in the rear was gps tracking, measuring speed, Once we settled on a  prop and gear ratio combo, it was painted nice and made to look pretty inside :} 
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grendel

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Re: Bulkhead mounted motors and gears
« Reply #11 on: September 18, 2019, 04:58:39 PM »

Tug Fanatic'
           Yes, I've used the Graupner Multispeed units in a few models with success.  A neat, simple and easy to install item but I suspect they are no longer available.


I've attached a couple of photos of my home-made version.  Just an aluminium plate drilled to accept the motor and prop tube as with the bulkhead mounting method.  The base being bent to match the hull it was to be glued into.  Still going strong in a tug model.


As for placing these posts in a "Beginners Section" in this Forum, a good idea but it's up to Martyn.


Glynn Guest
meccano gears?
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GG

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Re: Bulkhead mounted motors and gears
« Reply #12 on: September 18, 2019, 05:58:18 PM »

grendel,
          Yes, I have used Meccano gears in some models but I make a habit of collecting any suitable looking gears (and pulleys) and so have a bag of them to mix and match.


You can, of course, go down the route of buying them which can be expensive if you need to experiment before a suitable gear ratio is produced.


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grendel

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Re: Bulkhead mounted motors and gears
« Reply #13 on: September 18, 2019, 07:30:55 PM »

yes i agree old printers are a good source for drive shafts and gears
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rcboater1

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Re: Bulkhead mounted motors and gears
« Reply #14 on: November 08, 2019, 12:41:54 AM »

Back around 1990 or so, I used one of those Graupner units in a Matchbox Flower Corvette.   The thing worked well, but sounded terrible!  It was so bad I removed it and went with a direct drive solution.


In hindsight, Iíll be the noise was amplified by the big empty plastic hull.  But better meshing gears might have helped, too.....


Whatís a good source for suitable gears?  The issue I often run into is finding matching sets that will fit different diameter shafts- motors often have a larger diameter shaft than the propshaft....
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