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Old 09-22-2014, 08:21 PM
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Originally Posted by MaceH View Post
Nice job Richo!

Mine are crazy solid, but all wood- there is zero flexure.

A problem I have is that there are few folks here flying big planes- what one calls smooth I might call shaky. A good thing though is the planes aren't caring much either way... but smooth would sure be welcome.
My opinion of smooth is an engine that doesn't have a nasty vibration resonance period just above idle. This is mechanical vibration that can't be tuned out and is a product of design.

From there, I like an engine that doesn't have extreme combustion impulses at idle. This is the kind of vibration that shakes the control surfaces to pieces at idle or just above. This is a product of timing, combustion chamber design, compression ratio, etc. and can be affected very much by tuning.

Its all a matter of design compromise and highly affected by the need for getting that last bit of power out of a design.
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Old 09-22-2014, 08:23 PM
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I have two 3w110cs and they run truly smooth. I am thinking to buy a DA120, thatīs why I was asking.
The weight argument is valid, but all I can tell is that I save weight other places.
Would like a DA120 to my next project. I think I would try one.
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Old 09-22-2014, 08:30 PM
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Quote:
Originally Posted by Truckracer View Post
My opinion of smooth is an engine that doesn't have a nasty vibration resonance period just above idle. This is mechanical vibration that can't be tuned out and is a product of design.

From there, I like an engine that doesn't have extreme combustion impulses at idle. This is the kind of vibration that shakes the control surfaces to pieces at idle or just above. This is a product of timing, combustion chamber design, compression ratio, etc. and can be affected very much by tuning.

Its all a matter of design compromise and highly affected by the need for getting that last bit of power out of a design.
Good explanation- thank you sir.

Beyond mixture and timing, is there anything else that to be tuned? Sorry to hijack the thread...
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Old 09-22-2014, 09:09 PM
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One thing to remember is parts avalibility. I have a DL 100 and will never be able to get parts if I need them. I also have a DA 100 and will always be able to get parts for it. There are 3 or 4 versions of the DLE 111 and it's already hard to get parts for the earlier versions.
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Old 09-22-2014, 09:13 PM
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Originally Posted by MaceH View Post
Good explanation- thank you sir.

Beyond mixture and timing, is there anything else that to be tuned? Sorry to hijack the thread...
There might be minor differences in compression ratio between otherwise identical engines but I doubt that would amount to much in a quality product such as DA. My bet is most of the vibration differences are just the differences in airframes. Some very stiff and strong where others are wimpy at best.
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Old 09-22-2014, 09:16 PM
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Originally Posted by flatspinjim View Post
One thing to remember is parts avalibility. I have a DL 100 and will never be able to get parts if I need them. I also have a DA 100 and will always be able to get parts for it. There are 3 or 4 versions of the DLE 111 and it's already hard to get parts for the earlier versions.
Many engines become orphans over time. I know as I own several and they were name brands when they were new .... and none were DL or DLE.. The important thing is to fly an engine until it is used up and not just warehouse it.
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Old 09-22-2014, 09:20 PM
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That DL50 I have is way obsolete but it still hauls anything its been on like nobodys buisness.
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Old 09-23-2014, 09:36 PM
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Quote:
Originally Posted by Truckracer View Post
There might be minor differences in compression ratio between otherwise identical engines but I doubt that would amount to much in a quality product such as DA. My bet is most of the vibration differences are just the differences in airframes. Some very stiff and strong where others are wimpy at best.
+1
Airframe is the biggest factor in apparent vibration. I used to have a BME 95cc twin on a 50cc balsa airframe - it shook the beans out of that plane; I could see the stab moving up and down an inch at idle. It was a big engine for that size plane. Trashed the servos.


Later on, I put the same engine on a 75cc plywood airframe, where it appeared to run smooth as silk. On both planes, the engine was bolted directly to the firewall, no spacers.
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Old 09-23-2014, 11:42 PM
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As far as the DLE vs DA goes, I've had both and and I'd put it as simply as this, buy which one you can afford. I can afford DA's and that is what I buy now.
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Old 09-24-2014, 12:31 AM
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Quote:
Originally Posted by Truckracer View Post
There might be minor differences in compression ratio between otherwise identical engines but I doubt that would amount to much in a quality product such as DA. My bet is most of the vibration differences are just the differences in airframes. Some very stiff and strong where others are wimpy at best.
i havent run a DA120 so cant comment on that - but a huge +2 on the airframe design
i have seen it over and over, airframe design at the front end can affect apparent vibration of a motor BIG TIME.

recently had 3 x 123cc engines on 3 different airframes at the same airfield - ALL were setup and tuned by me on customers planes and 1 was my own plane. All 3 showed different vibration levels. the one that was the worst we decided to have a closer look, turned out the ply firewall was delaminating and was "soft" compared to the others. that translated to oscillations down the plane that looked terrible - new firewall was installed and suddenly its a different story and runs smooth!
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Old 09-24-2014, 06:06 AM
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Why not consider a GP 123.


Lower cost than the DA 120, fantastic customer service and lots of power.


I love my GP 123!!!!
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