Hi all,

can some one help me to reduice and isolate vibations caused by the the engine (MLD35 engine).

I dont know if the propeller balancing can reduice them!

 

any ideas?

 

Thanks,

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Welcome to the world of gas, diesel, and nitro.

 

I've flown nitro engines for 40 years and have switched to the EP world wholeheartedly... but then again, I no longer fly anything that would take a 35cc monster like that.

 

 

The prop MUST be balanced, otherwise your engine will suffer the effects and also your frame. With this engines, the vibration can not be totally isolated. There are several companies that sell vibration isolating mounts and standoffs , but my suggestion is to isolate the electric components to protect them from the vibration.

BTW, where are you trying to mount it? what kind of frame? balsa & play? composite? let us know so we can suggest you better ideas ;) I have experience with giant scale planes and also with this engines

Hello,

i use magic gel to protect electronics,

the problem isn't the plane but the the DCM algo, it doesn't work with this vibration.

I used also Isolation Mount GPMG2000.

 

 

Can i reduice vibration to 80%?

@

Ok you wont be able to reduce the vibration too much with this engines, but yes you can on the part you wanna isolate, you could try this Shock Absorving Sorbothane or any ther ani-vibration foam.

Hello Hamadivo,

 

I will not say this can't be done, however you are pushing water up hill on this one!

 

There are many factors to take into account, the slightest change in RPM will change the vibration frequency which is passing through the airframe, so if you have all the vibrations gone at, say 3000 rpm then another could start at 3200 rpm you remove that to find another at 4350 rpm and so on.

The main cause of the vibration will be the ignition cycle of the engine, think to those large powerful cars with very smooth engines, the reason they are so smooth and have a great deal less vibration is the number of cylinders used and very well balanced parts, now I know it would be great to have a straight 6, V8 or V12 plane engine which was very low in vibration with all parts balanced, however I don't see this happening any time soon!

 

So as said above the first thing you need to do is remove what vibration you can, the first step is to balance the prop, its not hard and will only take you a 20-30 min's max.

 

When you have that done you need to pull as much vibration away from the AP as you can while still fixing it to the frame to detect the movements made. This part will be a real trial and error exercise, I would try to find the best damping mounts you can for their size, I would recommend looking for some form of CD player from a car, they have small anti vibration mounts inside them to stop road surface vibrations transmitting to the internal workings, have you ever used a boot loading CD player? When you push your 6 / 10 CD cartridge in it feels firm but there is some movement there? Like it had a huge damping force inside? I think you should be able to find a broken one on ebay or at a scrap yard for not much and make a modification to it, you could always mount this on the foam or what every else starts to help reduce the main vibrations. I have not tested any of the CD players so can not say which would be the best, but I think using foam alone will lead to many hours of failed testing.

 

I hope this may have helped a little, apart from telling you to go electric, happy pushing!!

 

Regards

 

Martin

 

www.buildyourowndrone.co.uk

So many things can be done, as the example Martin gave. With this engines the vibration will always be and thats something to consider when trying to mount sensitive equipment.

I remember that one member here on the forum had the same problem with his APM, and he found a foam from an orthopedic matress that worked perfectly for him.

Here is the thread - http://diydrones.com/profiles/blogs/the-perfect-antivibration-foam

You can find a free kit of Tempurpedic foam here http://www.tempurpedic.com/our-company/information-kit.asp

Hope you solve it this time
BTW, Sorbothane is used for Nasa cameras on the shuttle.
not sure how the small engines like this are done but some fo the larger aircraft that i fly have flywheel weights on them to help counteract the vibrations and smooth things out a bit. might be something worth looking into
you might try a variable pitch prop and a governor to keep the rpms at the best balance between efficiency and vibration ,,,

1. Mount you engine on vibration isolation mounts

2. Mount all you electronic on isolation mounts

3. Try to use twin cylinder engine instead of single cylinder one. Twin engine significantly reduce the vibration

4. Keep the electronic equipments as far away from the engine as possible, hence UAV has engine way in the back and everything else in the front

Try the elastic band on each corner trick that can help, do balance the prop or that 35cc engine won't last long.

 

 

I cannot speak for RC engines but as I do build and repair my own car engine I can tell you the problem is universal. To reduce vibrations everything the spins must be balanced to reduce vibration. Reciprocating mass as described in engine tuning manuals is everything that can create a wobble (thanks to it being reciprocating :D) so the more you balance the less vibration you receive.

Jools Holland famously stated on Top Gear that the only perfect standard engine was a Jaguar V12 as you can place a 6 pence piece (old UK money) and start the engine and let it idle without it falling over.

Now I can only assume that an RC engine has just one piston making balancing like normal engine problematic. I assume that the largest difference is the prop so get that balanced after that isolation mounts would seem the only option except ripping the motor apart and balancing the little crank (assuming there is room to do so).

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