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Eaton Model 7

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Steve Addy08/02/2016 00:07:30
88 forum posts
41 photos

Does anyone know how much torque is required to control the Eaton Model 7 Hydrostatic drive? I'm thinking Arduino, fly by wire controlled by a servo.

I have the manual for it and have searched the Net without success.


Michael Gilligan08/02/2016 04:41:13
13234 forum posts
578 photos


I am not familiar with the product, but I woke in the night & it looks interesting


Although they don't mention a contol torque, they do suggest a 100mm lever; so I would think that a Servo for a model yacht would be ample.


Steve Addy08/02/2016 11:07:07
88 forum posts
41 photos

Hi Michael.

Your reply is appreciated.

I have the Model 7 fitted to the loco and the paperwork for it - I have even made the boss for the operating lever.

However, the only servos I have ever used are the standard type provided with a six channel RC outfit. I'll have to look up the figures for those, make a lever and buy a spring balance.


Circlip08/02/2016 11:25:58
945 forum posts

M6 allthread as a leadscrew with a reduction gear threaded onto it driven from a small motor, Jockey block on lead screw to give linear pull. Got to be cheaper than a servo with "Muscle."

Regards Ian.

Michael Gilligan08/02/2016 11:46:21
13234 forum posts
578 photos
Posted by Steve Addy on 08/02/2016 11:07:07:

I have the Model 7 fitted to the loco and the paperwork for it - I have even made the boss for the operating lever



A good alternative to the RC style Servo might be a Stepper Motor and toothed belt drive ... Only a little more complex Arduino-wise.


Bazyle08/02/2016 13:28:15
4581 forum posts
185 photos

sail winch servo, lever type. Cheaper ones available. Being an engineer you could use a rotary one and gears for even more torque.

Is the Arduino to give it some failsafe and automatic response to track signals? If plain RC checkout the loss of RF signal failsafe devices for planes and helicopters. Often thought 5in ground level could be fun with an RC shunter.

Since you have the device anyway it might be better to measure it running as any figures in the manual might be optimistic, not allow for old grease etc.

Edited By Bazyle on 08/02/2016 13:36:09

Steve Addy08/02/2016 20:18:06
88 forum posts
41 photos

Thanks again guys.

The idea of the Arduino is firstly that I know nothing about them and haven't written a program since the 80s.

I wish to make the loco work by using the gear levers in the cab and the throttle on the "backhead".

This would give the illusion of a mechanical gearbox with two speeds in forward and reverse. I would also like the engine revs to be beyond the control of the driver, determined by the gear position in forward or reverse with idle on neutral.

I haven't given it much thought yet, just weighing up what the servo might cost for starters. Standard servos I am used to are between 3 and 4 kilogram centimetres. I have just been looking up digital servos as I feared they needed a different control signal. It turns out this is down to internal pulses controlling the motor at 300Hz rather than 50Hz. They work on the same signal but have greater resolution and holding torque.

All interesting stuff.


Steve Addy24/02/2016 16:49:12
88 forum posts
41 photos

I have now bought an Arduino and written most of the code and it happily drives a standard servo in place of the more powerful things which will be needed. I have an all aluminium, steel geared Savox servo of 30kg cm torque to put the engine throttle beyond the control of the driver.

I have written to Eaton in the US, who passed it on to the distributors here; I got a nice reply with the wrong answer. They are now referring the question back to America.

Will win eventually.


Steve Addy18/04/2016 21:47:23
88 forum posts
41 photos

Just sent a final email to the UK agents - I assume they never got a response from America. Two months have elapsed since I last wrote to them!


Steve Addy19/04/2016 23:25:18
88 forum posts
41 photos

Further to my post yesterday, I got a very quick response from the chap concerned. Apparently they haven't heard from Eaton in America, but they have some units to test for a commercial user, so they will include the operating torque as part of it. I will post the results here assuming I do receive them. Fingers crossed.


Steve Addy23/10/2018 13:35:29
88 forum posts
41 photos

I never got a reply - fancy that!

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