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I need your help on Vibration

Old 06-06-2004, 10:28 PM
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rwfly
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Default I need your help on Vibration

Hello
I'm just starting into 1/4 scale and gas engine's. I have been told by respected people on RCU that these conversion engines will shake my glue joints apart and ruin my reciever and servo's. They do seem to have the money looking at thier aircraft to purchase what they want. I'm on a budget and have three Echo's some Homelite's and Weedeaters to convert but feel real lost at this point. I don't want to lose a plane and all the work due to vibration and would rather sell everything and buy a production R/C engine if this is the case.
I would arrpeciate you input and experience on this. Has there been any comparison vibration checks done on Factory R/C engine's and the conversion's?
I was told the difference was in the bearings and balancing of the crankshaft. I just made a prop hub for one of the Echo's and mounted it a heavy vice and fired it up with no prop to see how it turned and it looked great and the vibration didn't seem bad at all, although I'm sure the vice was absorbing some of this.
Thanks for your help. Best to all Ron
Old 06-06-2004, 10:46 PM
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xvz12
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Default RE: I need your help on VIibration

Well. if this is so, there's a whole bunch of people out here doing it wrong!! Until I started lurking out here, I had no idea how many weedeaters & chainsaws there were flying out there. IMHO, if you use good building techniques, balance your flywheels, & use adequate packing around receiver,etc., you should be just fine...at least I hope so, I've got three Homie 25cc engines already converted waiting for airframes, & hope to have at least one of them airborne in the next couple of weeks.
Old 06-06-2004, 11:04 PM
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Default RE: I need your help on VIibration

At idle, my conversions seem to shake the plane a little more than a glow engine. At any thing above an idle, the vibration, if any thing, seems less than a glow engine. (Possibly due to the lower rpm's and bigger props.) As a kid, I tried running glow engines clamped in a vise, and they always vibrated themselves right out! Scary! Somewhere in these threads, there is a pic of a guy holding a converted weedie engine with a prop and all, in his hand, running!! Not recommended for sure, but who would think of trying that with a glow engine??

In any case, I don't think it is something to worry about. The older engines from the '70's and 80's I have heard vibrated more, but I certainly haven't had any problems myself. I do specially reinforce the firewall area, as it is a heavier and more powerful engine.

Just my opinion,
AV8TOR
Old 06-07-2004, 10:37 AM
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Default RE: I need your help on VIibration

Hey guy's thanks for your replies, I'm feeling a little better already. It seems funny that there are so many doing this if the end result is a messed up aircraft. I would appreciate info on which engines are best and why so as not to make the famous beginners mistakes.

I'm lucky to have a friend who is a helper in a machine shop ( they are training him) and they let us go in after hours and use the lathe's, we even so far get free material from there scrap bin, pretty cool.

I bought one of the weedeater conversion kit's off eBay and notice the four screw hole's on the rear casing that you would use for the motor mounts are a course self tapping thread. The ones in kit are a finer machine thread but about the same diameter. Are you sopposed to re-thread these holes? It does not seem like there is enough metal left.
Thanks for your replies. Best Ron
Old 06-07-2004, 11:27 AM
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Default RE: I need your help on Vibration

HI,

I'm not sure about your question on the kit from e-bay. The most popular engines though, are the Ryobi's, Homelites, Kioritz/Echos, and some of the McCullochs work well. In larger sizes like 36cc plus, the Poulans are good performers and easy to convert.

AV8TOR
Old 06-07-2004, 02:38 PM
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Antique
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Default RE: I need your help on Vibration

I have been working on and converting engines for about 17 years..I have NOT seen ANY crank on ANY engine that showed signs of aftermarket balancing, contrary to anyone's advertising....It's pretty hard to make a mark on a crank that won't show up....Any balancing would show some holes drilled, weight ground off, or weight added...Sorry advertisers, it ain't there..
Old 06-07-2004, 03:40 PM
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smokingcrater
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Default RE: I need your help on Vibration

gas engines do seem to vibrate 'stronger' at very low rpms, especially at the nearly turning over idle point. (the firewall on my stinger 1.20 tore off before it every got off the ground!, had to fiberglass it) but at any normal rpm, it isn't as much problem, and might actually be less of a problem due to lower frequency.
Old 06-07-2004, 09:14 PM
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Default RE: I need your help on Vibration

Hi

go to

Ryan weed trimmer

and see my repply, a site with good photos, can help your friend machinist

good luck
Jose
Old 06-07-2004, 09:17 PM
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fokker38cc
 
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Default RE: I need your help on Vibration

Hi

I forgot

Ryan weed trimmer

is the post behind it

Jose
Old 06-08-2004, 10:32 PM
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rwfly
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Default RE: I need your help on Vibration

I want to thank everyone for their support and help. I have had emails sent and really appreciate your time. I'm back to the conversions so I hope you don't mind the future dumb question's. Best to all Ron

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