Desert Aircraft vibes

[2robinhood]

I currently own two DA-170's which I am running both of them on RE3 pipes and I love them.
I have owed two DA-150's and a DA-100L.
Those engines ran very smooth.
My two 170's run great and fairly smooth, but they are not the smooth that my 150's were.
Now I can't say this from personal experience, but I hear that the 120 shakes more then the 100 and people also say that the 60 shakes more then the 50 did.

So if the 60 shakes more than the 50, the 120 shakes more than the 100, and the 170 shakes more than the 150, is there a reason the newer engines are generating more vibes ?

Less crank mass ?

.

 

[Spats]

I have or had the 60, 120 and 170 and I really did not know that they shook so much until I switched over to GP. Not sure why they shake so bad but they sure do compared to the GP's.

 

[49dimes]

Post #9....Best answer

 

[Terryscustom]

I'm not a super engine technical guru but I do know how to operate and tune them properly. I've had two DA120's and they shake the crap out of the planes on the ground, and one can only assume what happens in the air but they are pretty brutal. However the power they produce is just off the hook. I've not owned a GP123 but I know for a fact that my GP176 shakes less than my DA120's. I currently have Two DLE120's, two DLE111's a DA100 and a DA100L and they are all equally smooth as silk and moderate power that does not compare to the 120.

Not any trash talking just saying what I've found through experimentation.....I won't sell my DA for anything and will probably have to try a GP123 at some point.

 

[49dimes]

I'm not a super engine technical guru but I do know how to operate and tune them properly. I've had two DA120's and they shake the crap out of the planes on the ground, and one can only assume what happens in the air but they are pretty brutal. However the power they produce is just off the hook. I've not owned a GP123 but I know for a fact that my GP176 shakes less than my DA120's. I currently have Two DLE120's, two DLE111's a DA100 and a DA100L and they are all equally smooth as silk and moderate power that does not compare to the 120.

Not any trash talking just saying what I've found through experimentation.....I won't sell my DA for anything and will probably have to try a GP123 at some point.

Hey Terry,

As much as Fergus wanted me to sell his engines I declined because the competitive nature in this particular part of the hobby is fierce!
I am not going to second guess any manufacturers proprietary technologies but the compression ratio and tolerances along with piston weight and ignition timing are some of the sought refinements in gaining performance in lighter but large packages. The DA 120 is extremely light for its displacement class and depending exactly where weight savings is best determined the piston plays a fairly large role along with the metallurgy used in all the components that make up the engine. An engine with a larger weight to mass ratio will operate more smoothly than a lighter weight to mass ratio.
In trying to address the OP's question he was specifically asking why the 120 over the 100, the 170 over the 150 and 60 over the 50.Finally the 123 over the 120. I know high silicon content aluminum is one of the refinements performance engine manufacturers are using in their designs.
Personally I do not think the 120 shakes bad at all once it is over 2000 rpm.

 

[stangflyer]

I'm not a super engine technical guru but I do know how to operate and tune them properly. I've had two DA120's and they shake the crap out of the planes on the ground, and one can only assume what happens in the air but they are pretty brutal. However the power they produce is just off the hook. I've not owned a GP123 but I know for a fact that my GP176 shakes less than my DA120's. I currently have Two DLE120's, two DLE111's a DA100 and a DA100L and they are all equally smooth as silk and moderate power that does not compare to the 120.

Not any trash talking just saying what I've found through experimentation.....I won't sell my DA for anything and will probably have to try a GP123 at some point.

I am happy to hear the DLE 111 runs silky smooth. I will be finding this out first hand really soon. Hope it is everything everyone says it is.

 

[49dimes]

Here is one thing I find very noteworthy of the DA 120....Acceleration! With big props! 29x9. When you punch a DA 120 it gets of its a$$ in no time.

 

[49dimes]

I know GP is coming out with a V3 123 and V2 61. I bet the shake more like the DA 120 and 60!

 

[Kevin-Young]

I have never been one of those guys who analyses the complexities of an engine such as bore and stroke and how they effect power but I think you can make a safe generalization when saying that any time you have a certain platform and then pull more power out of it with a larger displacement one of the biproducts will be more vibration.

In the case of the 60/120/170 one of the ways you can counteract the vibration increase is to make sure you are not using aluminum standoffs and use a wood mount because the wood mount will absorb some of the vibration. Also in some cases the airframe may be transferring a lot of vibration as well due to long motorboxes and lightning holes. You will also tend to see airplanes with built up wood wings seem to vibrate more because foam wings tend to absorb as well.

 

[49dimes]

I have never been one of those guys who analyses the complexities of an engine such as bore and stroke and how they effect power but I think you can make a safe generalization when saying that any time you have a certain platform and then pull more power out of it with a larger displacement one of the biproducts will be more vibration.

In the case of the 60/120/170 one of the ways you can counteract the vibration increase is to make sure you are not using aluminum standoffs and use a wood mount because the wood mount will absorb some of the vibration. Also in some cases the airframe may be transferring a lot of vibration as well due to long motorboxes and lightning holes. You will also tend to see airplanes with built up wood wings seem to vibrate more because foam wings tend to absorb as well.

You explained that very well. I know I have a bad habit. lol