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Do any of you guys use vibration dampening mounts 50cc? - 10/7/2011 3:54 AM   
Juker008


 

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Status: offline 		I wanted to ask if people here use dampening mounts for their gassers. Urethane, rubber, etc?

Thanks


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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 4:12 AM   
AirWizard



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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 4:23 AM   
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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 4:27 AM   
All Day Dan


 

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Status: offline 		The best way to dampen the vibration from an engine is to harness the kinetic energy in its moving parts, which causes the vibration, to as large a mass as possible. For us, that mass is the engine and airplane that needs to be connected as rigidly as possible. As soon as you break that connection with some form of isolation mount, you are asking for trouble. The RC manufacturers have designed their radios, especially the servos, to operate under some levels of vibration and you as the modeler can help that along with a good installation so there is no reason to isolate the two. Don’t do it. Dan.

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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 5:12 AM   
Tired Old Man


 

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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 5:27 AM   
Juker008


 

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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 5:53 AM   
Rcpilot


 

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Status: offline 		I do ...........

they're called wings.

I was taught to NEVER start a gas powered plane without the wings attached. They act as a vibration dampener. The guy who told this to me was a respected member with a lot of experience flying 100cc planes. So, I took him at his word and didn't question him.

A couple years later I watched a guy running a 50cc plane without the wings attached. I tried to stop him and told him I'd help him put the wings on if he'd just shut the motor off and let me help him. He told me, to go....... pack sand... ya know 4-letter words and a 1-finger salute. The guy was angry.

About 2mins into his 'engine break-in' the horizontal stabs blew off the airframe when he cracked the throttle wide open. I busted out laughing. I couldn't help myself. Seeing the look on his face after watching his stabs rip off as pieces of balsa and monokote strained through the fence behind his airplane..... priceless.

That right there convinced me. I never run a big plane without the wings attached.

Edited to correct spelling mistake....

< Message edited by Rcpilot -- 10/8/2011 4:08 AM >

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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 6:38 AM   
apalsson



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quote:

ORIGINAL: Rcpilot

I do ...........

they're called wings.


+1

The best vibration dampening for an engine in that class is a well balanced prop and well tuned engine

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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 9:33 AM   
pe reivers



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Status: offline 		I use D-lock rubbers (well-nuts) if I want to iso mount the engine. This is very similar to the ISO-mount system that MVVS provides for their gas engines.
These mounts are quite firm and work well if the plane is not the lightest of constructions. The plane needs to provide the seismic mass in the vibration system. With very low seismic mass, no damping is better.
Soft mounts tend to upset the carb mixture too much, unless extensively dampened, so most of the time are a PITA, and also cause broken mufflers and headers


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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 5:46 PM  1 votes
wind junkie



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Status: offline 		For good engine to plane power transfer performance, I'd never use isolation mounts.

In a past UAV project, we used a dampening mount to try to get the on board video and other sensors happy but there was a fair amount of engineering in that. As the previous poster implied , we needed to address the throttle link by rigidly mounting the servo to the motor assembly. There were a coulple RPM regions where the motor would shake, but otherwise it was tuned to be smooth for the cruise and max speed regimes.

Related to running with the wings on: Another thing to note is that a fiberglass fuse and/or open bay construction is not the best for soaking up engine vibration. Listen to a Carden compared to most other constructions styles and you'll hear its much quieter. For longevity and ease of maintenance, nothing beats a foam core (with balsa sheeting), wherever possible.

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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 6:01 PM   
Tired Old Man


 

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quote:

ORIGINAL: wind junkie

In a past UAV project, we used a dampening mount to try to get the on board video and other sensors happy but there was a fair amount of engineering in that. As the previous poster implied , we needed to address the throttle link by rigidly mounting the servo to the motor assembly. There were a coulple RPM regions where the motor would shake, but otherwise it was tuned to be smooth for the cruise and max speed regimes.




A "fair amount of engineering" to develop an effective iso mount is a massive understatement. Your comments about throttle linkage are 1,000% dead on the money. If the throttle servo is not an integral part of the engine assembly when using a good iso mount you will not have throttle linkage for very long. It would get ripped off the carb in short order. I use isolation mounts in similar applications but will not even consider something truly effective on a hobby model for numerous reasons, one of which is prohibitive development cost.

Unless you have a need to seriously isolate an optical payload, just hard mount the engine. If you have a real need to isolate a payload, first consider what will be involved to isolate ALL the various vibration sources. You'll find the expense of engineering and manufacturing to be far more than your imagery to be worth. Thousands of dollars of isolation mount development to gain a few images from what is for all intents and purposes a low budget, low quality camera.

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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 7:03 PM   
Juker008


 

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Status: offline 		Thank you everyone for your reponses.
I must say that I have given this some thought and tried to look at it from both perspectives. From the perspective of ISO mounting the engine, I'm looking at it as isolating the vibrations to the engine. With the use of eurethane mounts soft enough to isolate the vibrations to the engine, but stiff enough to keep the engine from flexing and producing angular thrust.
Looking at it from the perspective of hard mounting the engine. I understand that wood construction is somewhat flexible when compaired to other building materials, and can see how it alone can act as a dampener. It is that understanding that makes me question if using the firewall as a vibration transmission point and the fuse as the dampener the least stressful mounting option.

Perhaps some of you vets can put things into perspective and give me some analogies that would put this into better light.


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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 8:05 PM   
marcus doobus


 

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Status: offline 		I can tell you from experience, (and Jedi Jody can confirm this, as he was involved in the repair), I tried what you just described as a thought. DON"T DO IT! I used large neoprene washers, supported by large fender washers. The thought was to help the firewall a bit. I was using this system on a DLE 30. First I had the engine with the self made dampening system on my test stand for a slight break in and pretuning. Somewhere around the 3rd or 4th tank full, wham, the prop shaft broke off at the back plate. Thinking that it was just a defective single shaft adapter, I sent it in for a warranty replacement. After I received the replacement, I mount the exact set up into my Edge 540. During the 4th flight, turning final, wham. It did it again. This time I lost the entire aircraft. Jodi suggested after the warranty that I not do that, but Noooooo, this lunk head didn't listen. It cost me a beautiful aircraft!!!!!!!! I hope this helps?

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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 9:01 PM   
All Day Dan


 

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Status: offline 		Juker,
The consensus of opinion has been “Don’t do it.” We are all experienced flyers. What is there to think about? Dan.

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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 10:12 PM   
on_your_six


 

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Status: offline 		Answer to that question is; How can I improve the life of my electronic equipment and servos? Vibration isolation absolutely will help... I have experimented with neoprene washers sandwiched with fender washers and iso mounted the throttle and choke servos.

I did not seem to accomplish much vibration reduction with that approach. I did not have a way to measure before and after, so it was a gut feeling. Bottom line that I have learned is to use electric power vehicles in conjunction with video and cameras.

I am not disagreeing with others here... the best things to do are to balance the prop and spinner the very best you can. The guy that makes vibration isolation for small engines also does custom work for larger engines.


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ORIGINAL: All Day Dan

Juker,
The consensus of opinion has been “Don’t do it.” We are all experienced flyers. What is there to think about? Dan.



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RE: Do any of you guys use vibration dampening mounts 5... - 10/7/2011 11:19 PM   
Tired Old Man


 

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Status: offline 		An effective isolation mount will have a 30cc engine oscillating in about a 3" circle at 3,000 or so RPM. The harmonics of the combustion impulses cannot be avoided. To be effective you need a multi stage iso mount that will permit that amount of engine swing.

This is a hobby forum and if anyone wants the engineering involved with a good iso mount they need to be willing to pay for it. No free rides from this end. You'll be out about $100,000.00, not to mention production costs. All of it has already been done and put to effective use., making it a well proven piece of equipment, but it's not available to the public, and won't be.

< Message edited by Tired Old Man -- 10/8/2011 12:32 AM >

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RE: Do any of you guys use vibration dampening mounts 5... - 10/8/2011 12:25 AM   
Uncas


 

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Status: offline 		I used the Dubro anti-vibration Motor mounts on a Brillelli 46 to a GP Yak 54. The vibration did not seem any better or worse when I later mounted the engine with hard mounts. Now, this is not a scientific fact, just an observation and there is a big difference. The rubber isolation boots are hard and are compressed pretty tight, and I do not know what frequency is being filtered or I guess possibly amplified. I did not take vibration readings. I am sure a vibration spectrum analysis would have shown some differences but I could not really tell myself by touch. It would be an interesting thing to test, but you would need some good vibration equipment and someone who can read the data.

I did actually run the engine without the wings mounted and I thought the plane was going to explode.

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RE: Do any of you guys use vibration dampening mounts 5... - 10/8/2011 12:33 AM   
Tired Old Man


 

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RE: Do any of you guys use vibration dampening mounts 5... - 10/8/2011 12:35 AM   
aghost



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Status: offline 		I have a TF P-51 with a G62. If I was doing it again I probably would not put in vibration mounts (Vibra-Loc). However, I did back then. Four years later and almost a hundred flights, the firewall, throttle linkage, engine, etc. are OK. Could be because I beefed up the firewall, the G62 is a stout, heavy engine, and the plane has substantial mass.


The vibration mounts certainly don't take the place of a balanced prop and spinner and good engine mounting.

Brian

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RE: Do any of you guys use vibration dampening mounts 5... - 10/8/2011 2:14 AM   
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Status: offline 		I say hard mount a gas engine always...but lets take some of the ideas and make a landing gear shock isolater so the bottom of a lot of our airplanes does not get ripped out.  Seen it happen today on a not so smooth field.  There must be some kind of stiff rubber bushing you could use for the landing gear mounts to be in to take up the shock and let the gear move a bit.  The Idea is some flex permitted to avoid wood being ripped out of the bottom of your airplane.  Thanks   Capt,n

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RE: Do any of you guys use vibration dampening mounts 5... - 10/8/2011 4:12 AM   
Rcpilot


 

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quote:

ORIGINAL: Uncas

I used the Dubro anti-vibration Motor mounts on a Brillelli 46 to a GP Yak 54. The vibration did not seem any better or worse when I later mounted the engine with hard mounts. Now, this is not a scientific fact, just an observation and there is a big difference. The rubber isolation boots are hard and are compressed pretty tight, and I do not know what frequency is being filtered or I guess possibly amplified. I did not take vibration readings. I am sure a vibration spectrum analysis would have shown some differences but I could not really tell myself by touch. It would be an interesting thing to test, but you would need some good vibration equipment and someone who can read the data.

I did actually run the engine without the wings mounted and I thought the plane was going to explode.



Darn lucky it didn't explode. Glad you dodged a bullet that day. You still got that Brillelli?

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RE: Do any of you guys use vibration dampening mounts 5... - 10/8/2011 4:21 AM   
HunkaJunk


 

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quote:

ORIGINAL: Juker008

I wanted to ask if people here use dampening mounts for their gassers. Urethane, rubber, etc?

Thanks



I tried one once, but it made the vibration VIOLENT,  by the time I used stiff enough rubber to make the shaking stop, I just went ahead and mounted it right to the firewall.  I remember I balanced everything as perfectly as I could, prop, spinner backplate, and spinner were all balanced seperately with no luck.



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RE: Do any of you guys use vibration dampening mounts 5... - 10/8/2011 6:07 AM   
CHARLES WINTER



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Status: offline 		Hi Guys My 2 cents. Many years of flying all types of R/C airplanes. I bolt all my engines SOLID to the firewall. Never had a problem. Col. Chuck Winter

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RE: Do any of you guys use vibration dampening mounts 5... - 10/8/2011 8:09 AM   
Kweasel


 

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Status: offline 		Its easy to take out some airframe noise with firm rubber mounts but all the vibration will still be there. I made a large cradle mount with pneumatic pillows at each corner for an old UAV. Resonance could be moved around by adding weight/stiffness to the mount and different areas on the airframe. The engine would jump around alarmingly at lower rpms without some weight added. The helicopter company that I now work for has scientists spending millions to make the best of this zero sum game.

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RE: Do any of you guys use vibration dampening mounts 5... - 10/8/2011 11:08 AM   
Luchnia


 

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quote:

ORIGINAL: Rcpilot

I do ...........

they're called wings.

I was taught to NEVER start a gas powered plane without the wings attached. They act as a vibration dampener. The guy who told this to me was a respected member with a lot of experience flying 100cc planes. So, I took him at his word and didn't question him.

A couple years later I watched a guy running a 50cc plane without the wings attached. I tried to stop him and told him I'd help him put the wings on if he'd just shut the motor off and let me help him. He told me, to go....... pack sand... ya know 4-letter words and a 1-finger salute. The guy was angry.

About 2mins into his 'engine break-in' the horizontal stabs blew off the airframe when he cracked the throttle wide open. I busted out laughing. I couldn't help myself. Seeing the look on his face after watching his stabs rip off as pieces of balsa and monokote strained through the fence behind his airplane..... priceless.

That right there convinced me. I never run a big plane without the wings attached.

Edited to correct spelling mistake....


This is good info. I do run my Brison 2.4 through the entire throttle range without wings on a SIG 300XS often when tuning at my shop and I never have an issue. I suppose some engines, plane combinations and firewall mounts probably are different.

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