Right or Wrong way to set up linkages?
05-14-2008, 04:20 AM
#1
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Right or Wrong way to set up linkages?
Although I build my own and build for customers I have over the last few years noticed some major differences in the way people make and hook up linkages.
There are many on this forum with years of experience and it would be a great help to me to see what is considered the be tried and tested ways to achieve a good, solid, reliable slop free linkage set-up.
From my own experiences of building jets, manufacturers supply a very wide range of fittings, each opting for different styles of clevis, rod etc.... what's good, what's bad?
Photos of your set-ups and where to get the bits used would be really helpful, as would some of the technical reasoning behind the options, like making use of the full servo travel (if indeed this is important).
Maybe even a 'top 10' of things to try to achieve when setting up a linkage in order of importance...
marc.
There are many on this forum with years of experience and it would be a great help to me to see what is considered the be tried and tested ways to achieve a good, solid, reliable slop free linkage set-up.
From my own experiences of building jets, manufacturers supply a very wide range of fittings, each opting for different styles of clevis, rod etc.... what's good, what's bad?
Photos of your set-ups and where to get the bits used would be really helpful, as would some of the technical reasoning behind the options, like making use of the full servo travel (if indeed this is important).
Maybe even a 'top 10' of things to try to achieve when setting up a linkage in order of importance...
marc.
05-14-2008, 06:04 AM
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RE: Right or Wrong way to set up linkages?
Gary,
This I understand this is good practice, so do you cut your servo arm cut-outs big enough to allow the clevis to drop below the level of the hatch, or do you only allow travel to extend to close to the point of contact to the hatch?
marc.
This I understand this is good practice, so do you cut your servo arm cut-outs big enough to allow the clevis to drop below the level of the hatch, or do you only allow travel to extend to close to the point of contact to the hatch?
marc.
05-14-2008, 08:16 AM
#4
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RE: Right or Wrong way to set up linkages?
To me, the design of the linkage all depends on what the loads are likely to be for the surface in question. Not everything has to be over-engineered.
For something with extreme loads you might want to use the two-horn approach that Matt showed us pics of a while ago, together with the gizmos that some of the giant 3D aircraft use at the servo end - don't remember what they are called but they basically provide a second support for the final drive shaft of the servo. Both these approaches eliminate or reduce problems associated with off-plane torquing that causes wear and subsequent slop.
For other surfaces a simle 2-56 rod with a solder clevis on one end and a threaded clevis + jam-nut on the other is fine.
What I don't particularly like (though plenty of models use them) are plastic ball-links used in the hot end of the aircraft.
For the setup, ya gotta use as much of the servo travel as possible. Get a copy of the [link=http://members.cox.net/evdesign/pages/products.html]Envision Linkage Design[/link] and play around with the various parameters to see just how much you increase or decrease your margins when you change servo travel, horn length, etc. It's a very valuable tool IMO.
Gordon
For something with extreme loads you might want to use the two-horn approach that Matt showed us pics of a while ago, together with the gizmos that some of the giant 3D aircraft use at the servo end - don't remember what they are called but they basically provide a second support for the final drive shaft of the servo. Both these approaches eliminate or reduce problems associated with off-plane torquing that causes wear and subsequent slop.
For other surfaces a simle 2-56 rod with a solder clevis on one end and a threaded clevis + jam-nut on the other is fine.
What I don't particularly like (though plenty of models use them) are plastic ball-links used in the hot end of the aircraft.
For the setup, ya gotta use as much of the servo travel as possible. Get a copy of the [link=http://members.cox.net/evdesign/pages/products.html]Envision Linkage Design[/link] and play around with the various parameters to see just how much you increase or decrease your margins when you change servo travel, horn length, etc. It's a very valuable tool IMO.
Gordon
05-14-2008, 08:31 AM
#5
RE: Right or Wrong way to set up linkages?
Marc,
In most applications the linkage at the servo end is inside the hatch, so I do sometimes have to have a rather large opening in the servo hatch to clear the clevis.
One thing I forgot to mention is that I always set my flap servos with 180 degree motion so that I have no load on the servo at 0 degrees flap and no load at full flap (varies by application)
In most applications the linkage at the servo end is inside the hatch, so I do sometimes have to have a rather large opening in the servo hatch to clear the clevis.
One thing I forgot to mention is that I always set my flap servos with 180 degree motion so that I have no load on the servo at 0 degrees flap and no load at full flap (varies by application)
05-14-2008, 08:46 AM
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RE: Right or Wrong way to set up linkages?
Gordon, thanks for that, I might have to see if the software is available for Mac. Could you also send over a link to Matt's info you referred to - thanks.
marc.
marc.
05-14-2008, 08:51 AM
#7
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RE: Right or Wrong way to set up linkages?
I didn't bookmark Matt's posts that showed the linkage.
If I can find the info via some searches I'll update this post, otherwise hopefully someone else has the URL and can share it.
- - - - -
OK - I know I have seen better pics & descriptions, but this may help for starters:
http://www.rcuniverse.com/forum/fb.asp?m=6949951
http://www.rcuniverse.com/forum/fb.asp?m=2041350
http://www.rcuniverse.com/forum/fb.asp?m=3181296
http://www.rcuniverse.com/forum/fb.asp?m=3721966
http://www.rcuniverse.com/forum/fb.asp?m=6732065
If I can find the info via some searches I'll update this post, otherwise hopefully someone else has the URL and can share it.
- - - - -
OK - I know I have seen better pics & descriptions, but this may help for starters:
http://www.rcuniverse.com/forum/fb.asp?m=6949951
http://www.rcuniverse.com/forum/fb.asp?m=2041350
http://www.rcuniverse.com/forum/fb.asp?m=3181296
http://www.rcuniverse.com/forum/fb.asp?m=3721966
http://www.rcuniverse.com/forum/fb.asp?m=6732065
