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Author Topic: Motor direction/prop rotation?  (Read 3437 times)

Paul R

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Motor direction/prop rotation?
« on: September 29, 2006, 10:25:50 PM »

For a single screw scale model of a fast mahogany runabout for instance, is it usual to arrange so that the prop is turning ant-clockwise when viewed from the stern of the boat. The motor seems to turn quicker and easier with this arrangement with a positive voltage on it's pos terminal on the back of the motor. The motor in question is a 700bb turbo 9.6v. Or can the motor be run the opposite way so that a right handed prop can be fitted that turns clockwise when viewed from the stern? What are the benefits or disadvantages

Paul R

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Fast Electricals

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Re: Motor direction/prop rotation?
« Reply #1 on: September 29, 2006, 10:54:55 PM »

The 700BB has a small amount of advanced timing on the brushes, so will always run better in the forward direction. Reversing the wires will make the motor run with retarded timing which is inefficient and not recommended. It may be possible to rotate the end bell through 180 degrees and then adjust the timing advance to make the motor run efficiently in the opposite direction. I have done this with a modified motor fitted with a removable brush set but not on a sealed can motor such as a 700BB.

Have a look at this article for more information on timing.

http://homepage.ntlworld.com/fast.electrics/Timing.pdf

Neil

stobby256

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reversing a motor - how?
« Reply #2 on: September 30, 2008, 08:38:04 PM »

Hi All,

I'm going for a twin motor setup, but how does one reverse a motor (no I dont mean turn it around the other way...!)  :D

It will be a 700BB Turbo - I take it simply reversing the polarity is not all and it my have to be re-timed?

Thanks to all  O0

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Weeds

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Re: reversing a motor - how?
« Reply #3 on: September 30, 2008, 08:56:44 PM »

1 Use Forward/Reverse Speed Controller (ESC)
OR
2 Use servo that reverses polarity by turning an electric switch
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Shipmate60

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Re: reversing a motor - how?
« Reply #4 on: September 30, 2008, 09:06:51 PM »

I am not 100% sure but there is no mention of variable timing on the 700BB Turbo on the Graupner website, so I assume it is just wire up opposite to the ESC.

Bob
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John W E

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Re: reversing a motor - how?
« Reply #5 on: September 30, 2008, 10:08:53 PM »

hello there

Sitting here with a Graupner speed 700 turbo; I am unable to see any reference at all to 'variable timing'.   I have wired the motor up to a 6 volt battery; swapped the terminals over so it reverses the motor - but, I am unable to see any physical effect.

The only thing is says in the destructions  :D  is that the Graupner motors are permitted only to run for a short while - and this is the bit I cannot understand 'Suppression of Interference the motors are supplied pre-suppressed in order not to effect the safety of operation of radios - you should use an anti-interference filter, additionally (the 700 turbo 9.6 volt part number 3308 is not suppressed).   I think Graupner are telling porkies  :-X   one minute they say their motors are suppressed, but, this one ISN'T!!!!

Aye
John E
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Sandy Calder

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Re: reversing a motor - how?
« Reply #6 on: September 30, 2008, 10:31:03 PM »

For reversing,I'd give a ilink to an illustrative diagram if I knew where one was just now.
Using two changeover switches:- connect poles to motor and group the C annd N.C.terminal in pairs and then one pair to +ve,the other to -ve.Youl'd need to "snub" switch contacts or the huge inductive current would destroy contacts.
Just watch what such a motor does to battery terminals when you connect a 700 across them.

Speed controllers employ several methods. A full H-bridge type is similar to four on/off switches where the horizontal bar represents the motor.There are other ways too.

May I ask ,if you are using the 700bb Turbo for a vehicle or in a boat,what kind of boat,scale and prop do you want to drive?
If it happened to be a tug or scale ship then there are better motors for that.
If it is an M.T.B or fast cruiser be careful you don't over overload the 700BB Turbo with too large a prop.

If the motor behaves differently with reverse rotation then there is no way other to balance a pair than rudder or different throttle or coupling the motor in the opposite sense.I don't think changing the timing would solve that.You may find the difference of one motor to the next is as significant than the brushes bouncing.Is that what you are getting at?

There are are other ways to work around what I think you see as a problem.
Regards
Sandy Calder
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Stavros

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Re: reversing a motor - how?
« Reply #7 on: September 30, 2008, 10:34:01 PM »

I dont have a problem at all with the graupener 700 I run one in one direction and the other the other way they both rev up on fwd and reverse,personally I think you are trying to find a problem that does not exsist.Ther is no variable timing on the 700 series




Stavros
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toesupwa

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Re: reversing a motor - how?
« Reply #8 on: September 30, 2008, 10:39:20 PM »

Ask at the LHS for a Right handed 700 and a left handed 700...  O0

Or you could just swap the motor leads over..  ;)
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catengineman

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Re: reversing a motor - how?
« Reply #9 on: September 30, 2008, 11:32:28 PM »

My old 700 turbos were suppressed (internally) I still suppressed outside  O0 and with opposed rotation I have not seen or had any problems

R,
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andrewh

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Re: reversing a motor - how?
« Reply #10 on: October 01, 2008, 08:29:45 AM »

stobby

Reverse the wires, and it WILL run the other way ;D
Now there are two possibilities:
1 it runs at the same speed and takes the same no load current as its mate or
2 it behaves differently (it will not be a big difference)

If you find (1) then the motor is neutrally timed, and doesnt care which way it runs - Ahhhh the Cox reed-valve engines
if it is a case of (2) then one of the motors needs to be retimed (You still don't know which one has the correct timing for its rotation)
AFAIK ALL motors can be retimed, even if they are not designed for it and have swaged cases and end plates

I'm not able to give detail on retiming, but there are published procedures which the speed merchants have discovered.

But my (less than perfect) understanding is that "Speed" motors come very nearly neutrally timed, since Graupner can't guess whether you are going to go for direct drive, geabox or belt drive ;D

Also: most "Speed" motors, but not all of them have a built in capacitor between the brushes (you can often see the terminal wire coming out of the case and wrapped roung the terminal tag).  This is much better than nowt for radio supression, but it is very sensible to also fit a full supression kit to a high power brushed motor - three (more) capacitors.

Hope this helps a bit
andrew
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stobby256

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Re: reversing a motor - how?
« Reply #11 on: October 09, 2008, 01:56:52 PM »

Ok - just a question - some lively debate here and Im grateful for all of it.  I'll simply swap the wires over  :embarrassed:

But, which one goes which way -- does the LH one go clockwise/anticlockwise, and or the RH one go anticlockwise/clockwise?

Does it really matter? ok2

Oh sorry - its for a mono hull power boat, I'm keeping the prop size to 40-50mm to avoid overloading!
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andygh

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Re: reversing a motor - how?
« Reply #12 on: October 09, 2008, 04:05:51 PM »

I believe the convention is, when looking from behind the boat left hand prop=clockwise, right hand prop=anticlockwise, in other words the blades move towards each other at the top and away at the bottom. Does that make sense?
I'm not sure if reversing this would be critical with model boats
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stobby256

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Re: reversing a motor - how?
« Reply #13 on: October 09, 2008, 04:08:57 PM »

 :-))

At last a *sensible* answer...  {-) and one not involving jewellery  :kiss:

Cheers  :-))
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Martin [Admin]

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Shipmate60

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Re: reversing a motor - how?
« Reply #15 on: October 09, 2008, 05:45:34 PM »

It really depends on the rudder configuration

Bob
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catengineman

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Re: reversing a motor - how?
« Reply #16 on: October 10, 2008, 05:51:13 PM »

It really depends on the rudder configuration

Bob

and a lot of other stuff including vessel owners pref's

ok2
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Martin [Admin]

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Re: Motor direction/prop rotation?
« Reply #17 on: October 14, 2008, 01:35:33 PM »


Just did a quick web search for prop rotation and stuff like that.....
Tell you what, forget all your twin sticks, channel mixing, external mixers, that's old hat!


I want a miniature MerCruiser Axius® control system!!!!

http://www.mercruiseraxius.com/
http://www.mercurymarine.com/engines/inboards/sterndrives/axius.php
http://michiganboatingandoutdoors.com/home/twin-prop-handling.html
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tobyker

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Re: Motor direction/prop rotation?
« Reply #18 on: October 15, 2008, 12:19:11 AM »

Impressive. Do you think I should start the chinese destroyer again to incorporate one? %%
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