Angus McDonald

Hi Guys, I'm new to gas and wondering how close is too close to mount a servo for throttle control, I'm thinking of a couple of engine positions and one would suggest I mount the servo about 2 inches away from the coil and pick-up...how much of a negative effect if any will the coil/high tension lead or pick-up have on the servo?

Thanks for reading

Angus

carlosponti

My Feedback: (1)

the rule of thumb i have heard is around 12 inched away from the engine. mounting in the firewall will have adverse problems. i would say if you are serious about trying it do a range check with the engine running and without the engine running. but i have a feeling you are going to have problems.

Tired Old Man

My Feedback: (1)

Depends a lot on how well you pay attention to the quality of the equipment you intend to use, and the manner in which you set everything up. The 12" rule of thumb was originally designed in the days of mostly magneto engines and early ignition systems. It's extremely common today to see throttle servos mounted on or very close to the engine mounting box to take advantage of a direct shot with the linkage and/or a balance situation.

Some people pay little attention to much of anything and just slam a plane together, ending up with nothing but electrical problems. Those that do a good job with good equipment rarely have any problem at all.

bob_nj

My Feedback: (62)

In situations where I didn't have another choice but to mount the throttle servo in an other than
ideal position, I've used fiber optic extensions with good success.

If you do a search on this board you'll find some good threads on the subject.

I got mine here, although the information is minimal on the site for some reason.
[link=http://forgues-research.com]optic[/link]

Good luck_bob

Zeeb

My Feedback: (41)

I had the same questions initially, but lots of posts from people like Silversurfer posting here and the factory location for the throttle servo on my Edge convinced me to go ahead with it. I also have the choke servo mounted in the bottom of the engine box in a very similar manner, the setup works fine...

You have to pay attention to the no metal to metal contact rule and it should work without problems.


Oh, in case you are wondering, the pic is not the final install. Just one I took while setting things up. The final install includes fuel proofing the entire area under the cowl and all the screws installed in the servo mount... [8D]

Angus McDonald

Thanks Guys, I appreciate the responses, haven't decided what to do yet but will do a significant amount of testing if I mount it close to the engine.

Angus

exeter_acres

My Feedback: (2)

for my DA- 50...the servo is in the motor box with a 4.5" Titanium turnbuckle....
NEVER a problem for me...

carlosponti

My Feedback: (1)

no matter where you install it or whos advice you follow know that you should follow my advice and test the setup before flying with it. better safe than sorry.

Tired Old Man

My Feedback: (1)

Agreed. To pun an old saying...range checks, don't leave the ground without 'em.

carlosponti

My Feedback: (1)

clever i like that!

JettPilot

My Feedback: (6)

I put my radio battery and throttle servo within one inch of the ignition system coil with almost disastorous results [X(] Was the shortest pattern I ever flew, climb for a few seconds going in and out of fialsafe, shut engine down with just enough altitude to get turned around and land [sm=47_47.gif] Sometime it works, but sometimes it does not [:@]

Range Check WITH the engine running.

JettPilot

NM2K

My Feedback: (14)

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And a good job is providing plenty of separation between the R/C flight system wiring/electronics and the engine's electrical system. This means no firewall or near firewall mounted servos.

Since we humans cannot perceive electromagnetic radiation with our eyes, we must rely upon rules-of-thumb. As with all rules-of-thumb, sometimes they work and sometimes they do not, but at least they are a fairly conservative starting place.

Our R/C receivers "see" in the electromagnetic radiation spectrum. The less excess background radiation there is, the more clearly the normal objects in this spectrum can be perceived. In the real world, there is no black or white - just shades of grey, so to speak. There is always some electromagnetic background light. The point is to keep the unwanted electromagnetic emissions to a minimum, so that our receivers can more easily perceive the radiation that we wish to pick up and utilize. The easiest way to diminish the unwanted radiation is to increase the distance between the components.

Keeping components well separated helps dim this unwanted "light" that is caused by normal engine operations, thus making the signals that we do wish to receive stand out better.

Since there is no way to completely prevent the radiation from the ignition system from invading our receivers (grey - no black or white), it is our job to keep this unwanted radiation to as low a point as possible. Again, physical separation of the components of the R/C system and the ignition system is the best method, however there are other tricks we can employ, if necessary. Ferrite beads placed upon the long leads of our servos can help lower the background noise considerably, if conventional tactics are insufficient to provide us with a low enough noise floor.

Price of equipment is no indicator of suitability in this instance. Modulation scheme makes absolutely no difference at all in net performance. It does make a difference in how interference is displayed to the operator, but no modulation scheme will save your model if the ignition noise is getting past the RF section of your model's receiver. For those not technically oriented, PCM can hide problems that should be addressed. That is why I set up my gassers with FM (PPM) receivers first, sort out the bugs and after the model has been flown successfully/satisfactorily with FM, I then switch to PCM for such features as failsafe, finer servo resolution, etc.