Dubro swivel ball links safe?
08-22-2003, 09:25 AM
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Dubro swivel ball links safe?
I just picked up a pack of a dozen Dubro swivel ball links to use for all of the control linkages on my GP Extra 300S 60. They look like just what I want to minimize slop and friction, but I'm concerned about how they connect to the control horn with a bolt and nut. There's no locknut or lock washer and it seems like there is potential for the nut to fall off which could cause a loss of the airplane.
Has anyone had this problem? Any ideas on how to secure the nut? Thread lock? Safety wire?
Lee
Has anyone had this problem? Any ideas on how to secure the nut? Thread lock? Safety wire?
Lee
08-22-2003, 11:01 AM
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Dubro swivel ball links safe?
Just put a drop of medium CA on the nut after you tighten it down. It will be plenty secure.
OTOH, these DuBro ball links develop radial slop between the ball and the plastic link fairly quickly. I dunno whether it is due to the metal ball being "soft" or the plastic link wearing prematurely, but it does occur. I've seen it on several models now, including a couple of UCD's that are flown aggressively.
A much better (and much more expensive) way to get that super smooth, super free range of movement that ball links provide is to purchase some links and balls from a reputable helicopter manufacturer. Helicopters are much harder on control linkages, on average, than airplanes. The material is produced accordingly.
Having been involved with helicopters since 1992, I find that the links by Miniature Aircraft, makers of X-Cell helicopters, are as durable as they come. They are molded to fit the MA balls on the tight side. The purpose of this is so the link can be "fitted" to the ball; a simple, quick procedure involving smooth-jawed pliers. They will "wear in", or fit themselves, to the ball eventually, but will be on the stiff side until this occurs.
I say this is much more expensive because, in addition to purchasing the balls and links, you must make your own pushrods, since the links are intended for 2 or 2.2mm diameter rod material. 2/56 is too large. The stuff to get is 2.2mm drill rod from a metric supply house. It can be difficult to find. And, of course, you must purchase a die to cut the threads. All this sounds like a tremendous amount of hassle. Its not; making your own pushrods opens up an entire new vista of versatility in your model's set-up. And the 2.2mm drill rod is plenty sturdy; much more so, in fact, than the generally dead-soft 2/56 wire pushrods normally supplied with kits and ARFs.
You can buy links for 2/56 rod from Nelson Hobbies. These are the old Rocket City brand, and are equally excellent. But you will still need balls and 1.5mm bolts or screws to attach them to the horns. And the balls from different manufacturers are not always the same size. There is supposed to be an industry standard, but...
I always found the balls from Kalt and TSK to be the most uniform. Naturally, both firms are defunct now. Next best that I have used is the afore-mentioned Miniature Aircraft.
Sorry for the novel, here. If you are interested in pursuing it, PM me and I'll give you some more details, including a pic of how to "fit" the links to the balls.
Steve
OTOH, these DuBro ball links develop radial slop between the ball and the plastic link fairly quickly. I dunno whether it is due to the metal ball being "soft" or the plastic link wearing prematurely, but it does occur. I've seen it on several models now, including a couple of UCD's that are flown aggressively.
A much better (and much more expensive) way to get that super smooth, super free range of movement that ball links provide is to purchase some links and balls from a reputable helicopter manufacturer. Helicopters are much harder on control linkages, on average, than airplanes. The material is produced accordingly.
Having been involved with helicopters since 1992, I find that the links by Miniature Aircraft, makers of X-Cell helicopters, are as durable as they come. They are molded to fit the MA balls on the tight side. The purpose of this is so the link can be "fitted" to the ball; a simple, quick procedure involving smooth-jawed pliers. They will "wear in", or fit themselves, to the ball eventually, but will be on the stiff side until this occurs.
I say this is much more expensive because, in addition to purchasing the balls and links, you must make your own pushrods, since the links are intended for 2 or 2.2mm diameter rod material. 2/56 is too large. The stuff to get is 2.2mm drill rod from a metric supply house. It can be difficult to find. And, of course, you must purchase a die to cut the threads. All this sounds like a tremendous amount of hassle. Its not; making your own pushrods opens up an entire new vista of versatility in your model's set-up. And the 2.2mm drill rod is plenty sturdy; much more so, in fact, than the generally dead-soft 2/56 wire pushrods normally supplied with kits and ARFs.
You can buy links for 2/56 rod from Nelson Hobbies. These are the old Rocket City brand, and are equally excellent. But you will still need balls and 1.5mm bolts or screws to attach them to the horns. And the balls from different manufacturers are not always the same size. There is supposed to be an industry standard, but...
I always found the balls from Kalt and TSK to be the most uniform. Naturally, both firms are defunct now. Next best that I have used is the afore-mentioned Miniature Aircraft.
Sorry for the novel, here. If you are interested in pursuing it, PM me and I'll give you some more details, including a pic of how to "fit" the links to the balls.
Steve
08-22-2003, 11:39 AM
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Dubro swivel ball links safe?
You may want to put a small washer under the head of the bolt, just make sure it is larger than the balls outside diameter. This will prevent the plastic part from coming off after its broke in. As far as the nut goes, get slighly longer bolts and nylok nuts. 
Steve
Steve
08-22-2003, 02:52 PM
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Dubro swivel ball links safe?
The nut coming off is the least of your problems. As stated above, use locktite or CA on the nut. Use the washer as well to make sure it can't come off.
I personally will not use plastic anything when it comes to controls on power planes. I have had plastic clevises wear from vibration and pull off the rods after a couple years of flying, which caused the plane to spin in uncontrollably. Hate it when that happens. I only use metal and Z bends. Thats just me though.
I personally will not use plastic anything when it comes to controls on power planes. I have had plastic clevises wear from vibration and pull off the rods after a couple years of flying, which caused the plane to spin in uncontrollably. Hate it when that happens. I only use metal and Z bends. Thats just me though.
08-24-2003, 12:05 AM
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Dubro swivel ball links safe?
I used dubro swivel ball links on many planes & my nephew used all dubro swivel ball links on his 35% cap. No problems @ all, they are great & are priced right. Just use a little red thread lock on the bolt before screwing the nut on & tighten good.
Gil
Gil
