Model Boat Mayhem

The Shipyard ( Dry Dock ): Builds & Questions => Submarines => Topic started by: 6705russell on October 26, 2009, 08:42:40 am

Title: What size motor?
Post by: 6705russell on October 26, 2009, 08:42:40 am

I am currently building a WTC for a Victor class sub, what size motor would be recommended? The sub measures 70 inch length.....

Thanks

Russ

Title: Re: What size motor?
Post by: das boot on October 26, 2009, 08:50:32 pm

Russ, when I built mine(or started to build it)I installed an ex-car heater blower motor to propel it along, using a(I think)80mm seven bladed scimitar prop.


Rich

Title: Re: What size motor?
Post by: 6705russell on December 01, 2009, 08:07:01 am

Thanks Rich,

The only snag i have got is that i have only made the access for the motor quite small ( first time build and all that!) so ideally i am looking for a motor say the size of a Graupner 600/700 that will turn a 90mm prop? Am i whistling in the wind? Do i need to make some mods on the tray?

Thanks

Russ

Title: Re: What size motor?
Post by: Mankster on December 01, 2009, 09:28:57 am

Hey Russ, thats pretty good. I am afraid you will need a larger motor that that on direct drive. A Graupner 720 Torque may just about work, or one of those  tug boat motors from Mobile Marine, or even a Hectoperm.

Title: Re: What size motor?
Post by: 6705russell on December 01, 2009, 12:33:48 pm

Thanks Mankster

I wont be running the sub flat out all the time, just the odd pass now and again, i will try the Graupner and see if it fits ok.

Russ

Title: Re: What size motor?
Post by: Subculture on December 01, 2009, 12:59:25 pm

You will burn out your motor, I guarantee.

Looks like you have room for a bigger motor, or fit a planetary gearbox,  5:1 possibly more depending on the free running RPM of the motor. 1500-2000 RPM is what you should be aiming for.

Title: Re: What size motor?
Post by: Mankster on December 01, 2009, 01:54:39 pm

MFA do a big range of motors with planetary gearboxes in various reductions.

Title: Re: What size motor?
Post by: 6705russell on December 01, 2009, 02:38:14 pm

Thanks guys, what is the ideal ratio?

Russ

Title: Re: What size motor?
Post by: Subculture on December 01, 2009, 04:34:10 pm

That depends on the free runnign RPM of your motor.

Like I said, at least 5:1, and aim for an RPM of somewhere between 1000-2000 RPM under load, free running RPM could be upto 25-30% higher. A 90mm diameter prop should move an awful lot of water. Some experimentation might be in order to arrive at the right ratio.

Title: Re: What size motor?
Post by: Sub driver on December 01, 2009, 06:08:45 pm

Try a Robbe Navy Compact 3:1 ( I think ) reduction and prop shaft attached.
Will easily move a boat that size on 6V. its a 600 size can about the same size as you pic.

About £25.00 all in.

you can just see it with the orange gearbox in the top pic in my module.



Regards.

Sub.

Title: Re: What size motor?
Post by: Subculture on December 01, 2009, 06:18:20 pm

Only problem is, 600's come in such a wide variety of winds. 3:1 sounds a bit optimisitic unless it's a very mild wind indeed.

Title: Re: What size motor?
Post by: Sub driver on December 01, 2009, 06:52:00 pm

Russ

It has a gearbox of 3:1 ratio or maybe 2.3 :1. Not the wind of the motor

Anyway here is a pic, it easily propels my 65 inch Vanguard an a 65 inch L.A and even comes with mounting lugs.

 
Regards Sub

Title: Re: What size motor?
Post by: Subculture on December 01, 2009, 07:22:21 pm

Fair enough, but how big is the prop on your vanguard, 2.5" diameter?

This one is a 4" prop.

Title: Re: What size motor?
Post by: Sub driver on December 01, 2009, 07:32:04 pm

Hi,

4 Inch ?

Is he making butter ?????

Mine are a 10 blade 3" Dia, and the one on the L.A is a Larger one, 7 blade Scimitar.

Just a thought for him to consider all options, with a 4 " prop I would definitely reccomend some type of gearbox though...just my thoughts.

Regards
Sub.

Title: Re: What size motor?
Post by: Subculture on December 01, 2009, 07:57:43 pm

Don't forget a 70" victor is much bigger scale than a 1/96th scale Vanguard. 1/48th I believe.

Andy

Title: Re: What size motor?
Post by: 6705russell on December 01, 2009, 09:03:16 pm

Hi guys

Yes the Victor is a big sub, she measures a touch over 6 foot and around 9 inch diameter at the bow tapering to 2inch by the prop. I will get some pictures on tomorrow where i am upto with the build, i think i will need to reconfigure the motor/servo tray to fit a geared motor in...

Thanks

Russ

Title: Re: What size motor?
Post by: 6705russell on December 02, 2009, 11:25:53 am

Hi all

I was looking at this MFA motor?

http://www.maplin.co.uk/Module.aspx?ModuleNo=43373

Any input on this one?

Thanks

Russ

Title: Re: What size motor?
Post by: Mankster on December 02, 2009, 12:27:57 pm

Thats the one I have in my Sheeline Trafalgar, it will be too weeny for your sub. Go for the 942D51 (540 size motor) or 975D41 (800 size motor?) instead.

http://www.mfacomodrills.com/pdfs/gearbox_colour_brochure_1-15.pdf