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Motor gearbox for USS Susquehanna

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During the lockdown I have tidied my loft !  and dragged out the Imai USS Susquehanna.
This is a simple but vey nicely moulded kit even by todays standards.

I would like to sail it as an rc model but whilst I have plenty of experience with rc gliders but I am all at sea  :o when it comes to knowing what size motor and gearing is required for a paddler.  The model is about 500mm long with an 85mm beam.
Draught is pretty shallow at around 22mm.

As I am not much of an engineer, I wondered about using on of the Tamiya motor gearbox units.  These all seem to have the final drive via hexagonal 3mm shafts which ae too shot to each the paddles. I can't find any hexagonal steel of this size and wondered if brass would be adequate to un paddle to paddle. 

Steering is intended to be by rudder rather than differential paddles, due to the small displacement. I realise that a substantially enlarged rudder will be needed.

Any helpful comments gratefully received.

Welcome Paul

This vessel size sounds for the need of caution :nono

If the hull is complete, could I suggest you place the hull in the bath, then gently add weight/mass to bring the hull down to the intended waterline

A simple method could be say an empty 675 ml plastic drink bottle.......then add water to the bottle as the needed weight etc

Take this bottle & weigh on the kitchen digital scales the weight of the plastic bottle + weight of the water volume total will confirm to you the total weight of batteries+motor/gearbox+RC gear+ battery that you must not exceed  :shoot

These days, Google will provide you with a detailed confirmation of the individual mass etc

The image here is an array of M3 brass electrical standoffs that could be used as paddle shaft extensions [can also be contoured in an electric drill]......the weight here appears as 20gms.......

Let us know how you progress with your weight/mass displacement tests



Hi Derek,
             I scavenged a pile of weights, sellotaped the hull halves together and used electrical tap to mark the waterline.
The ballast to get it to the waterline was  0.68 kg   which I managed before the Sellotape let the wter in :)
I weighed the sprue carrying the main deck and the large display base, which weighed 0.20 kg  and this is a more than generous amount for deck, funnel, masts, spars, rigging and paint.

That leaves 0.48kg or a shade over 1 pound in imperial measurement., for battery, motor/gearbox, rudder servo and a smoke unit.

A brief article on motorising Susquehanna appeared in the November 1981 issue of Model Boats magazine but it doesn't provide any useful information about the motor/gearbox. Th only interesting comment was that the builder omitted each alternate paddle blade and felt that sailing trials suggested that was a good decision.

So back to moto/gearboxes and ratios ???  any thoughts ?

Thanks for responding by the way.

No sorry Paul.......these light weight values are way out of my league/knowledge......... Derek

Derek,  can you perhaps help with the sort of speed I want for the paddlewheel ?


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