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HomeAircraftHelicopterSynergy R/COther › Why are the plastic ball links tight before sizing?
06-25-2015 11:07 PM  3 years agoPost 1
00boto

rrApprentice

Kennesaw, Ga

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We have been seeing a few questions lately about the sizing of ball links and why. Below is my reasoning for keeping the design of Synergy ball links tight.

Plastic is one of the most versatile materials on the planet today. However, there are challenges when dealing with injection molded plastic parts.

- Plastic parts are injection molded at very high pressures in order to reduce the amount of shrinkage after the part has cooled. However, you can only reduce this so much. Shrinkage must be accounted for in the design so that the part comes out within the correct tolerance. This has little to do with why the Synergy links are tight, it's just a bit of information so that you know the difficulties in making plastic parts correctly.

- As most of you know, many materials if not all expand and contract with cold and hot temperatures. Heat expands the link making the ball link ID loose, cold contracts making the ball link tight. If a ball link is made to fit perfectly in a controlled environment around 72 degrees Fahrenheit what happens when you fly in cold or hot weather? In cold weather, you are probably okay, in hot weather you better worry about those links that were perfectly fitting at 72F.

This is why Synergy chooses to let the pilot size their own ball links to suit their geographical location as well as personal preference. Could I make a link that fits perfectly? Yes! But knowing what you know now about plastic, why would you want that? These are the fine details that go into a high quality helicopter which most take for granted and some find annoying.

I hope that helps explain the critical nature of properly sizing your ball links.

Thanks,

Matt Botos

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06-26-2015 03:58 AM  3 years agoPost 2
hawk3319

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Sand Lake, MI - USA

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With working in the injection molding industry, Matt has nailed it. Everything he has said is 100% correct. When I design parts for vehicles I have to take the same in account, as well a 100 of other factors. Keep doing what your doing Matt, awesome heli. Matt if you need another manufacture let me know.

Hawk

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06-26-2015 04:09 AM  3 years agoPost 3
ESWLFSE

rrElite Veteran

Liberty Hill, TX

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Whats your opinion on ball polishing? I like to hit mine lightly with some 1500 while chucked in a drill, then a quick polish with the Dremel buff and some compound. This must reduce their diameter ever so slightly, and they seem smoother in the links.

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06-26-2015 02:51 PM  3 years agoPost 4
gwright

rrVeteran

Champaign Il

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I plan to just send my links and balls to Ben <G>. I've heard his procedure is to store the links and balls in a perfectly temperature controlled 72 degree house for many hours so they're all temp stabilized. He then PERFECTLY fits each link to each ball, keeping the matched pair, ball and link,.. together. Then they're installed on the machine ensuring that the proper ball goes with the proper link.

The really funny thing about the above statement is that most will think I'm joking.

If you want a PERFECTLY built machine, just duplicate everything Ben does. Unfortunately I don't have anywhere near that sort of patience.

GW

Gary Wright

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06-26-2015 04:50 PM  3 years agoPost 5
Santiago P

rrProfessor

South West, Ohio

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his procedure is to store the links and balls in a perfectly temperature controlled 72 degree house for many hours so they're all temp stabilized. He then PERFECTLY fits each link to each ball, keeping the matched pair, ball and link,.. together.
Only Ben would think of such draconian methods. LOL

I bet all that is done in a sterile chamber or bubble, at zero gravity so the sizing is not biased by gravity...

Jokes aside, kudos to Matt for a well thought process.

Chago

Team Minicopter - PeakAircraft.com
bavarianDEMON- Team Kontronik - Scorpion Motors-

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06-26-2015 04:50 PM  3 years agoPost 6
Dr.Ben

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Richmond, VA, USA

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lol Gary. Yeah all links are indeed indexed to a given ball.

RE what Matt was saying and especially at this time of the year, I had initially my E5SS pitch rod links in A/C to be a fuzz snug. I went to the field when it was about 95, and they were too damn loose. So I came home and sat the front steps after it had cooled down to about 85d and sized a new set out there. Those are a better average fit across the temp range.

Kissing balls with fine sandpaper is fine. I dislike any further sizing via ball sizing because the wear point over time is often the ball, so I would rather have the leeway over time when slop appears to just fit a new link.

Sizing links takes time, but it's a hell of lot less annoying than precisely heating sloppy links with a heat gun to tighten them up. Try doing that 22 separate times on an old school FB model like I used to fly years back.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

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06-26-2015 05:06 PM  3 years agoPost 7
rexxigpilot

rrProfessor

Florida

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I would NOT recommend the average modeler using sand paper on link balls. Unless you're experienced with polishing metal parts, you will likely leave behind micro scratches that will eat up the plastic links quickly. If you must resize the balls, use micro-fine wet dry sand paper and progressively sand the metal starting with 1000 grit or finer and finishing with 4000 or finer. Then use a polishing compound and wheel to get it ultra smooth.

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06-26-2015 06:39 PM  3 years agoPost 8
Dr.Ben

rrMaster

Richmond, VA, USA

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Agreed. When anything but ultra fine stuff is used, the link on the sized ball may have the right tension but still is not smooth.

Ben

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

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06-26-2015 08:42 PM  3 years agoPost 9
bkervaski

rrElite Veteran

Birmingham, AL, USA

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Gary,

Trying to find someone to polish your balls for you?

Bill

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06-26-2015 08:45 PM  3 years agoPost 10
gwright

rrVeteran

Champaign Il

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Ha..................Ha

Gary Wright

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06-26-2015 10:05 PM  3 years agoPost 11
Chuck Bole

rrElite Veteran

Tulsa Ok. U.S.A.

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Back in the day i used a Hypersizer. Always had to squeeze the link a little to get it to cut properly. The Botosizer works extremely well. Never had a Synergy link break or pop off since 2007, without hitting the dirt first anyway.

I swear sometimes it seems like they grow back too! I'm sure it's just a change in temp though.

chuck

Team Synergy Field Representative / Thunder Power

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06-27-2015 03:13 PM  3 years agoPost 12
rexxigpilot

rrProfessor

Florida

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As Matt mentioned in his original post, solid materials expand when heated and shrink when cooled. The rate at which various materials do this is known as the coefficient of thermal expansion. The lower case Greek letter alpha is used to represent the coefficient in equations. Every material has a different alpha.

The ideal for a link would be to use metal and plastic link materials with close enough alphas so they expand and contract at about the same rate. This would allow sizing to close tolerances and not having it change with changes in temperature.

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