Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Radio Equipment => Topic started by: kiwimodeller on May 13, 2009, 05:42:09 am
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Hi, I know this can be done using a Y lead but how well does it work? Do both usually move the same amount? I am thinking of setting up the throttle on my single cylinder steam plant and the reversable pitch propellor on the same channel so that when I go to change from forward to reverse the engine revs drop. Also this would mean that when the load was light (not much pitch) the throtle would be partly closed. The only thing left to work out is how to get full throttle again when I go to full reverse pitch. The alternative is to buy another radio with more channels which I am trying to avoid. Is it possible to have twin sticks on one side of the set? All ideas welcome. Thanks, Ian.
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As long as you use two similar servos then there's no reason why they should move different amounts. Ref the radio, you'll find that the Robbe-Futaba F-series "Navy" version has a twin "split" stick on the LHS.
A Y-lead would be a cheaper option!
FLJ
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The aircraft guys do it all the time. Larger model aircraft quite often have two servos on the ailerons on one wing, and double on tail rudders. Just use the same type of servos.
John
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hi all
What FLJ forgot about was his little gadget - the 'servo-stretcher P96' - %% - with this little gadget you can alter the 'throw' of your servo on one side; so, if you wire it up with a 'Y' lead so that you have a standard servo one side controlling your variable pitched prop; the other side of the 'Y' lead you plug in the P96; and, from the P96 you plug in a standard servo connected to your throttle. This will give the ability to adjust the movement on your throttle for reverse. Food for thought :-))
aye
john e
bluebird
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Thanks for that all. Bluebird, is the P96 a Futaba item? Thanks, Ian.
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hi ya there mate, the P96 is an ACTion product, I am unsure of the price. They are though, a good little gadget, you can do a good few things with them. You can actually slow the servo down as well with them and also link 2-3 of these units together to get them to do different movements.
Hope this helps. http://www.action-electronics.co.uk/mixers.php
aye
john
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Hi Ian,
We've discussed similar problems on the Paddleducks forum regarding flash boiler control and the use of PIC controllers.
As you know I had a simlilar requirement for controlling direction and throttle from one channel, which, although achievable by using PICs, I reverted to two channels as a more practical solution.
I have made and programmed a small PIC board for my reversing gear and drains valves (see http://www.modelboatmayhem.co.uk/forum/index.php?topic=15501.0 ), which can be programmed for just about anything that has one servo input and up to three servo outputs.
The downside of the solution is having to gain the skills to build and program such a device.
Have you considered a mechanical solution of a crank arm coming off the pitch servo and operating the throttle. As the pitch servo turns through say 90deg, at zero deg it could represent full reverse pitch and full throttle - at 45deg, zero pitch and minimum throttle and at 90deg, full forward pitch and full throttle. The P96 would be useful for extending the 90deg movement to 160deg (check their data) and give greater control over the required movement to the throttle.
Of course you could use two separate servos from the same channel and suitable crank linkages, if the throttle and pitch mechanical controls are not physically close.
Would a sketch be useful?
Ian G.
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Kiwimodeller
What you describe sounds exactly what I have to do with my Werdna brushless reversing device - I need to close the throttle, move a servo (in this case operating microswitches) then advance the throttle to proceed in t'other direction.
I have used a spare channel to do this and it works fine as long as the brain stays ahead off the boat.
I'm interested in the replies you are getting , and still hopeful that Mayhem ingenuity can offer a solution which can be done within a single channel.
I have the impression that you have two channels only and ideally don't want any more?
andrew
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As long as you use two similar servos then there's no reason why they should move different amounts. Ref the radio, you'll find that the Robbe-Futaba F-series "Navy" version has a twin "split" stick on the LHS.
A Y-lead would be a cheaper option!
FLJ
just to add to your reply Dave , the guy should also make sure that tha Y lead is not a reversing type like the aircraft lads use .
There are two types available.
daz
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Hi there Portside II
Could you clarify this reversing Y lead as the only way to reverse a servo that I know of, is to do it electronically with an electronic circuit - I know you can get Y leads with an electronic reversing unit built into them, but, these are a lot more expensive than a standard Y lead. As far as I am aware, you cannot reverse a servo just by swapping the polarities over on the wires.
aye
john e
bluebird
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Just for info, servos can be reversed, but both the motor wires and the two outer pot wires have to be reversed.
(I've never done it, never needed to)
andrew
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And to throw another Ian into the pot, what you're trying to do Ian (Kiwi) is change the propeller pitch from full forward to full reverse and slow the engine down to tickover at the zero pitch point and then re-speed it up as you're going to full reverse pitch?? Looks like an electronic (Servo) solution for the Pitch control but a two way mechanical for the throttle. Whether the prop is travelling in forward or reverse pitch, the enginge is rotating in the same direction at both extremities.
Regards Ian, (third)
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Probably not much practical use on this topic but my first 1:1 scale boat had a single lever remote control for the outboard motor. Neutral was centre then you could move it backwards or forwards to either engage forward or reverse gear and then further to open the throttle. The whole thing was done using a system of cams in the control box connected to bowden cables to the gear and throttle controls on the motor itself. The geometry of the internal mechanism was quite clever and worked perfectly with no electronics to go wrong.
Colin
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Hi,
Here's a sketch of a mechanical set of linkages driven from one servo, although a servo could be used for each linkage as long as the throttle was acting radially from its servo and the pitch was acting tangentially from its.
Ian G.
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Hi John , i may have got it wrong but here goes.
on an airplane with ailerons a Y lead is used to connect both servos together , with the servos opperating in opposing directions
http://www.servoshop.co.uk/index.php?pid=FUTLYLEAD&area=Accs .
When opperating flaps a Y lead is used so that the servos opperate the same way,
http://www.servoshop.co.uk/index.php?pid=JP7721044&area=ACCS .
I think thats right {:-{ .
daz