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Old Nov 06, 2011, 03:38 PM
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DeeBee1's Avatar
United Kingdom, England, Brighton
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Question
Small Servos for Diesel/Glow Planes

What make/model of servo do you guys use for small R/C planes powered by diesel or glow (40" or less like an R/C converted Tomboy or similar)?

I usually use Futaba or Hitec servos for electric planes but their ranges of smaller servos (sub-mini, micro etc.) state that they shouldn't be used with IC engines, due to vibration I guess. Do you simply risk it with small servos or are there some made for IC?

The lightest I can find that is suitable is 21g. Any suggestions?
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Old Nov 07, 2011, 07:05 AM
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I've been using 8 gram HS-55 and HS-45B's in 1/2A Texaco planes with no problems as do many guys we fly with. I have a Brown Jr powered plane using HS-82MG's also and again they work great. I've never heard of the "do not use with IC engines" statment so went looking. Futaba in thier chart indicates smaller servos for small plane and electric ,but then Hitec just indcates plane with no power or size exceptions.

Hitec chart: http://www.hitecrc.de/store/servo_chart.html

Futaba chart: http://www.futaba-rc.com/servos/servochart.pdf
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Old Nov 07, 2011, 07:25 AM
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A HS-55 would certainly be inadequate as the elevator servo for a typical ".40 size" glow plane.

I don't see why it wouldn't work for "radio assist" of a 40" free flight airplane. If balance allows, I'd mount it near the control surface and far from the engine.
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Old Nov 08, 2011, 02:36 PM
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Thanks guys. I've flown larger IC planes with standard servos and all sizes/types of electrics with standard/mini/micro servos. Just no experience with small IC RC.

Leadchuker - I noiced the Fuataba 'small planes' servo types the other day but wasn't sure if they meant IC as well as electric. Spektrum give aircraft type advice e.g.:

http://www.spektrumrc.com/Products/D...rodID=SPMDSP60

Hitec give recommendations in their product descriptions e.g.:

http://www.hitecrcd.com/products/ana...ini/hs-55.html
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Old Nov 08, 2011, 05:07 PM
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But do any of them actually say they can't be used with IC engines ? That was what you originally claimed wasn't it ?

Anyway I think the 4-6 g servos are probably a bit small. I've often seen HS55s and standard 9g servos used with no problems (not tried 'em myself in IC models cus I've converted everything except C/L stuff to electric ). Going slightly bigger something like Hitec HS81s, commonly used as aileron servos on 40-size models like the Wot 4, would have no trouble and even they are only 16g.

Steve
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Old Nov 09, 2011, 02:59 AM
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My thinking of radios with converted Free Flight models is definitely in terms of "radio assist": ensure safe take-off and landing, suggest to the airplane that it should remain over your field. More for trim than maneouvering. Then surfaces and deflections will be small, as will the forces on the servos.

Others might not share this thinking.
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Old Nov 09, 2011, 10:39 AM
AMA7224 LSF1832
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Quote:
Originally Posted by perttime View Post
My thinking of radios with converted Free Flight models is definitely in terms of "radio assist": ensure safe take-off and landing, suggest to the airplane that it should remain over your field. More for trim than maneouvering. Then surfaces and deflections will be small, as will the forces on the servos.

Others might not share this thinking.
I would share the same thinking in general. Forces are probably closer to thermal duration sailplanes except for the very high powered glow competition old timers under power that climb like rockets. The smaller and sport flying old timers don't fall into the rocket climb catagory normally.
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Old Nov 09, 2011, 03:09 PM
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Quote:
Originally Posted by slipstick View Post
But do any of them actually say they can't be used with IC engines ? That was what you originally claimed wasn't it ?
Yes it was, although I'm sure the manufacturer's sites used to state this more clearly. However, I have found some examples of this being stated at Tower Hobbies (see the Comments section) of the link below:

http://www3.towerhobbies.com/cgi-bin...?&I=LXNCV8&P=7

Anyway, I think I agree that as for free flight assist of smaller models, smaller servos are probably fine.
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Old Nov 12, 2011, 12:17 PM
Sticks, Tissue & old Diesels
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Hi all,
This interests me because my next build is going to be a Super Buccaneer reduced to 36" span (an old RN kit bought on eBay).
Concerning the servos, I think the simple fact is that oriental manufacturers just donít realise that there are nuts like us flying RC with ED Babies, Darts, Mills & Amco, etc. For them, small RC means electric, and i.c. means powerful engines. In any case, weíre not sufficiently numerous to represent a significant market (there ainít many of us still running around loose!).
However, Iíve reached the (totally unsupported) conclusion that a well designed and properly damped servo mounting is unlikely to result in a servo being damaged by an ED Baby or Mills .75... with a few obvious precautions like balancing propellers, etc.
Anyway, Iíve purchased some 4g servos and some 8g. Iím going to try the 8g in the Super Buccaneer and I donít anticipate any problems...
Finally, Iím out in the sticks with no proper Internet and Iíve only just found these forums, but no doubt my Super Buccaneer efforts will be put online.
Brian
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Old Nov 12, 2011, 03:57 PM
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Hi Brian

Welcome on board! We are supposed to have 4 meg broadband down here in the Limousin as we are only a couple of kilometers outside Rochechouart which is (allegedly!) an ADSL hub, but my speed checks rarely produce better than a half meg - manage to get by OK though. May I ask where the devil you get your diesel fuel from - I would love to lay my hands on some so that I could build a KK Pirate 2 channel model for my Kalper (well, actually just a second fuselage to use the flying surfaces from the electric one). I fly only electric these days, but have a Mills 75, an AE 0.5 and a Bee as well as the Kalper.

There are some great build logs on this forum, can I interest you in building a Frog model for the build-off? See http://www.rcgroups.com/forums/showthread.php?t=1510260

Regards

George
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Old Nov 13, 2011, 09:35 AM
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Quote:
Originally Posted by brokenenglish View Post
Hi all,
Anyway, I’ve purchased some 4g servos and some 8g. I’m going to try the 8g in the Super Buccaneer and I don’t anticipate any problems...
Hi Brian, welcome to the forum.

I would avoid using sub-mini/micro servos (< 5g) for anything other than indoors as they can be quite flimsy. I recently had to replace two such servos on some small electric indoor flyers - one disintegrated and one just stopped working. I agree that something around 8-10g (e.g. Hitec HS-55) should be robust enough for a small diesel. Now that some small 2.4GHz receivers can be powered by very light and small lipos, a slightly heavier servo just results in the same overall net weight (if that makes sense).

The problem is that if a servo dies in-flight, the plane won't suddently become a free-flighter, the chances are that a control surface may become jammed fully up/down/left/right, followed by the inevitable crunch!

PS - Lovely Kalper you've got there Sundancer. They used to be made quite close to where I live In Southwick in East Sussex by Seymour, Hylda & Co. (a few years before I was born though).
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Last edited by DeeBee1; Nov 13, 2011 at 09:46 AM. Reason: Added a bit!
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