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  #1  
Old 08-24-2021, 06:38 PM
jclark jclark is offline
 
Join Date: Jan 2005
Location: Columbia, SC
Posts: 837
Default "Whole lotta shakin' goin' on ..." 2nd try. Any ideas?

Short version:

Initially: RV6 (2002), over 2000 hours with a carbureted Lyc O-320 [conical mount] and Hartzell CS prop at the end. One Jeff Rose EI and one P-MAG. Ran smooth. No issue.

Now: Fuel injected (AFP) 340 "Stroker" + Whirlwind 200RV prop.

Issue: When I pull back on the throttle in flight there is a "shudder". Think reducing throttle for landing. Think adjusting throttle in formation.

Prop and FI systems have been removed and verified as in good working order by Whirlwind and AFP.

No apparent induction leaks.

ANY IDEAS as to what MIGHT be causing this?

(I have bounced this off many people but no solution yet. So I appeal to the vast warehouse of "all things RV" knowledge.
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Columbia, SC
RV6 Flying, RV6A Cowling
APRS
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  #2  
Old 08-24-2021, 06:48 PM
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Bob Martin Bob Martin is offline
 
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Location: Charlottesville, Virginia
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Default

Have you balanced the prop yet......
pretty sure you have as WW says to do it ASAP.

When I am faced with similar issues I change things out....do you have access to another prop?
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Bob Martin
RV-6, 0-360 Hartzell C/S, Tip up, 1200+TT
James extended cowl/plenum, induction, -8VS and Rudder. TSFlightline hoses. Oregon Aero leather seats.
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  #3  
Old 08-24-2021, 07:13 PM
Low Pass's Avatar
Low Pass Low Pass is offline
 
Join Date: May 2006
Location: Houston
Posts: 2,117
Default

Quote:
Originally Posted by jclark View Post
Short version:

Initially: RV6 (2002), over 2000 hours with a carbureted Lyc O-320 [conical mount] and Hartzell CS prop at the end. One Jeff Rose EI and one P-MAG. Ran smooth. No issue.

Now: Fuel injected (AFP) 340 "Stroker" + Whirlwind 200RV prop.

Issue: When I pull back on the throttle in flight there is a "shudder". Think reducing throttle for landing. Think adjusting throttle in formation.

Prop and FI systems have been removed and verified as in good working order by Whirlwind and AFP.

No apparent induction leaks.

ANY IDEAS as to what MIGHT be causing this?

(I have bounced this off many people but no solution yet. So I appeal to the vast warehouse of "all things RV" knowledge.
My first impression is a problem with the elastomeric engine mounts. But I believe you have an imbalance to excite the system. No reciprocating aircraft engine experience to match this condition, but based upon my old machinery engineering days, it sure sounds like one of the things I would look at first.
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Last edited by Low Pass : 08-24-2021 at 07:19 PM.
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  #4  
Old 08-24-2021, 07:26 PM
jclark jclark is offline
 
Join Date: Jan 2005
Location: Columbia, SC
Posts: 837
Default

Quote:
Originally Posted by Bob Martin View Post
Have you balanced the prop yet......
pretty sure you have as WW says to do it ASAP.

When I am faced with similar issues I change things out....do you have access to another prop?

THANKS!

1. Prop was smooth running but I sent it to WW for "overhaul".
2. Got it back and immediately felt "prop vibrations". Attempted to have it balanced by local A&P shop. Could not get good numbers.
3. Sent it BACK to WW (at their request) and they re-did the work to check everything and got it to "0.0 degrees on the static balance".
4. Put prop BACK on and now it seems to be as smooth as before but have only done one flight as I have to wait to get the balancing done.

I **WILL** get it balanced though as the prop designer (Jim) pointed out that it makes a bigger difference than one might think.

I do NOT have a prop to test. It would have to be a fixed pitch for 180 hp, 1/2" bolts. Anyone with such just lying around, please send me a note.
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  #5  
Old 08-24-2021, 07:28 PM
jclark jclark is offline
 
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Location: Columbia, SC
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Quote:
Originally Posted by Low Pass View Post
My first impression is a problem with the elastomeric engine mounts. But I believe you have an imbalance to excite the system. No reciprocating aircraft engine experience to match this condition, but based upon my old machinery engineering days, it sure sounds like one of the things I would look at first.
They COULD be a problem but they are in fact new. I am accustomed to getting those changed out every 400 hours as I am VERY sensitive to vibrations.

Nothing LOOKS out of order with them. But I will check again.

THANKS.
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  #6  
Old 08-24-2021, 07:35 PM
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DanH DanH is offline
 
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Sounds a lot like the prohibited range for the McCauley prop on the IO-360-A1B6D (or was it the A3B6D?) in a Mooney 201, which was "avoid continuous operation between 1500 and 1950 RPM with power settings below 15 inches Hg manifold pressure".

When installed on an RV-8, the combination was a real shaker inside that range.
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  #7  
Old 08-24-2021, 08:19 PM
jclark jclark is offline
 
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Location: Columbia, SC
Posts: 837
Default Hmmmm ....

Quote:
Originally Posted by DanH View Post
Sounds a lot like the prohibited range for the McCauley prop on the IO-360-A1B6D (or was it the A3B6D?) in a Mooney 201, which was "avoid continuous operation between 1500 and 1950 RPM with power settings below 15 inches Hg manifold pressure".

When installed on an RV-8, the combination was a real shaker inside that range.
I think that the hub used in my vintage of WW prop is of McCauley descent.

I wondered if there might be a prop governor issue but did not think about the HUB. WW now machines their OWN hub as I recall.

Wonder if that is worth a discussion as I may be the ONLY person running my combination (Dual <but dofferent> EI + Conical mounts).

THANKS!
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  #8  
Old 08-25-2021, 06:57 PM
jclark jclark is offline
 
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Location: Columbia, SC
Posts: 837
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Quote:
Originally Posted by jclark View Post
THANKS!

1. Prop was smooth running but I sent it to WW for "overhaul".
2. Got it back and immediately felt "prop vibrations". Attempted to have it balanced by local A&P shop. Could not get good numbers.
3. Sent it BACK to WW (at their request) and they re-did the work to check everything and got it to "0.0 degrees on the static balance".
4. Put prop BACK on and now it seems to be as smooth as before but have only done one flight as I have to wait to get the balancing done.

I **WILL** get it balanced though as the prop designer (Jim) pointed out that it makes a bigger difference than one might think.

I do NOT have a prop to test. It would have to be a fixed pitch for 180 hp, 1/2" bolts. Anyone with such just lying around, please send me a note.
First, I have NO reason to suspect my Whirlwind prop. I wonder though about the hub based on DanH's comment but have no data or basis for real concern.

Having said that, I have been offered a loaner prop (THANK YOU to the person making the offer) but it was a metal prop and this engine needs something that absorbs the pulses. Therefore, wood or another composite is needed. Only Whirlwind has been willing to offer and stand behind a constant speed prop for this engine/ignition. I have also used a fixed pitch Catto (three-blade).

So if someone has something "lying around" it needs to fit the above criteria.

Still open to ANY thoughts or wild ideas to think about that you may have on this matter.

Thanks in advance.
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  #9  
Old 08-25-2021, 07:40 PM
Ralph Inkster Ralph Inkster is offline
 
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Location: Calgary, Alberta
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I assume you checked for any mechanical interference like baffling rubbing on cowling, tail pipes rattling against mount/floor/cowling, snorkel cowl rubbing, etc.?
The 340 would twist the engine mounts more than the 320 probably/maybe.
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  #10  
Old 08-25-2021, 08:28 PM
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gmcjetpilot gmcjetpilot is offline
 
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Default

Quote:
Originally Posted by jclark View Post
Short version:

Initially: RV6 (2002), over 2000 hours with a carbureted Lyc O-320 [conical mount] and Hartzell CS prop at the end. One Jeff Rose EI and one P-MAG. Ran smooth. No issue.
Side note my RV-4 had similar set up. It took Lord Conical Mounts and a good Prop balance to get it smooth. It was not like your current situation, but no low RPM shutter just high vibration levels all the time. You now have new engine with Dynafocal mounts or your original O-320 with conical mount? If you don't have LORD mounts regardless get them. If you still have conical mount... GET LORD MOUNTS TODAY. That might solve it.

Quote:
Now: Fuel injected (AFP) 340 "Stroker" + Whirlwind 200RV prop.
This was a 320 up to 340? There are 340's which are low compression 360's. So a "stroker" does change the vibration harmonics by itself. The prop is also experimental. Once you modify engine, stroke it (not a certified configuration) and put non certified props on that non certified engine, with non certified EI possibly, you have a very experimental system. Certified props get flight tested extensively with strain gauges and vibration measurements at all RPM's and MAPS. It is possible you are going through some transient harmonic vibration mode. Does this happen on ground run ups?

What little I know about Whirlwind 200RV I assume it is similar to a MT, wood blades with composite wrap and metal leading? The blades should be very vibration tolerant, and resistant to fatigue. The hub is metal and of course subject to metal fatigue. I would not think the HUB is the issue in shutter? Usually the blades themselves mostly vibrate not the hub. Did you talk to the Prop maker? Call or write them with details of everything and ask if vibrations might be an issue.

Quote:
Issue: When I pull back on the throttle in flight there is a "shudder". Think reducing throttle for landing. Think adjusting throttle in formation.
When RV's pull back power abruptly can get back fires and protest from the engine. Possible it is really shaking and vibration is transmitted through baffles hitting cowl and engine mount. Vacuum leak? You state you checked the induction tubes? Ignition may be involved? Do you have magnetos or EI? What if you pull power back really really slow? You should avoid abrupt throttle changes and Lyc states that in their technical data. Worse are counterweight cranks and engines with gear boxes which you don't have.

Quote:
Prop and FI systems have been removed and verified as in good working order by Whirlwind and AFP. No apparent induction leaks.

ANY IDEAS as to what MIGHT be causing this? I have bounced this off many people but no solution yet. So I appeal to the vast warehouse of "all things RV" knowledge.
Just hanger flying no brainy idea.
> Lord Engine mount vibration isolation, especially if Conical
> Balance prop again (I had to get mine balanced twice, the first guy was not good, the second balanced helicopter blades and world of difference)
> FI has been checked but make sure no induction or vacuum leaks
> Ignition wild guessing
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Last edited by gmcjetpilot : 08-25-2021 at 08:52 PM.
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