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HelicopterScale Model RC Helicopters › Retract module - where to get one?
09-02-2009 01:07 PM  8 years agoPost 1
Nevans

rrNovice

Coleshill,Warwickshi re,England

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I'm looking for a retract module for my Airwolf. I know that LHC used to manufacture one, but they no longer stock it. I need a module to control three servos, one reversed channel and end point adjustment for each channel. If anybody has built one of these, I am willing to pay for the details to construct one myself.

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09-02-2009 03:16 PM  8 years agoPost 2
JetDoc

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Germany

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You need one of these, great bit of kit. JR Matchbox:

http://alshobbies.com/shop/lookupst...p?pc=4519&Desc=

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09-02-2009 03:46 PM  8 years agoPost 3
Nevans

rrNovice

Coleshill,Warwickshi re,England

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Thanks JetDoc, that looks just the job!

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09-02-2009 06:30 PM  8 years agoPost 4
steve69

rrApprentice

Berkshire, UK.

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I bought one of these just last week from this seller, arrived in two days, does all that you have asked including reverse of one of the outputs.

http://cgi.ebay.co.uk/3-Channel-Ser...id=p3286.c0.m14

hope this helps


Steve.

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09-02-2009 06:53 PM  8 years agoPost 5
Nevans

rrNovice

Coleshill,Warwickshi re,England

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I have placed an order for a matchbox, but will probably order one of those too

Question: can I put a servo slow unit in front of the matchbox?

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09-02-2009 07:24 PM  8 years agoPost 6
steve69rrApprentice - Berkshire, UK. - My Posts: All  Forum  Topic

To be honest I dont know, I am just getting into scale at the moment.

I would imagine that the matchbox is a much better piece of kit but I could not justify the cost myself.

With retracts I believe you should attempt to always use the full 180' of travel from a proper retract servo rather than trying to use endpoints on a normal servo as the load on a normal servo trying to hold the weight of a model will either burn out the servo or drain the battery fast.
The idea on retracts is to 'over cam' the mechanical linkage so the weight is held by the linkage not the servo so you should create your travel adjustment by using the correct size servo arm (ie, make your arm/ball link to whatever length needed even if that means not using original servo arm holes)

Sorry if you already know all this, dont mean to insult.

There are quite a few threads about setting up mechanical linkages around here which is where I have gleaned what information I have.

There are a lot of really knowledgeable guys here that seem to be more than willing to help out a new guy.

Below is my 109 sitting on the the retracts but no servo is fitted, the weight is held up by the linkage alone, you can see the white arm with the cut out touching the black knob with the metal link rod going down to the gear, this is just 'over cammed' ie just past straight so all the weight sits on the black knob. I will try sort out another pic from inside the fuse if you like to show it better.


Steve.

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09-02-2009 07:40 PM  8 years agoPost 7
jackheli

rrProfessor

Vancouver - Canada

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You can get it much cheaper from here

It's easy to find an excuse to do wrong. Hard is not to find an excuse to do right.

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09-02-2009 08:13 PM  8 years agoPost 8
Nevans

rrNovice

Coleshill,Warwickshi re,England

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The retracts that I'm using lock mechanically at the end of their travel, so there is no load on the servos. It still requires the end points to be set accurately though; hence the need for the individual end point adjustment.

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09-02-2009 08:35 PM  8 years agoPost 9
steve69

rrApprentice

Berkshire, UK.

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As I said, if you are using proper retract servos then they will only travel 180' (or whatever the number is on the particular servo), end points have no effect on true retract servos due to their design.

If using normal servos you need to set your linkage so that full maximum travel is used by way of where you mount the ball link on the servo arm. This does away with the need to use the matchbox.

Using standard servos is generally not considered good practice as a standard servo works differently electronically to a true retract servo and draws a lot of power when holding station unlike a proper retract servo.


Steve.

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