What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

"Whole lotta shakin' goin' on ..." 2nd try. Any ideas?

jclark

Well Known Member
Benefactor
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.
 
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?
 
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.
 
Last edited:
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.
 
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.
 
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.
 
Hmmmm ....

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!
 
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.
 
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.
 
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.

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.

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.

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
 
Last edited:
No apparent interference

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.

No signs of interference.

Yes, the pulses are stronger on the 340.

Thanks!
 
Thanks. Keep the ideas coming!

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.

The SAME Conical mount with new Lord "donuts" Stroked 320 with compression upped to 9:1. Will inspect, again. This airplane (320/Hartzell CS config) has been flown rather aggressively (Team RV /Team Aerodynamix airshows) with those mounts and no problem.

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?

Per the blade designer, the engine was actually tested with the prop that I have (Whirlwind).

I tried to get the same results on the ground but have NOT been able to do so as of yet.

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.

Extensive dialog has been held with Whirlwind. They have been very good. Prop has been sent back to them to double-check everything. I had them do the full "overhaul" just in case (the prop has only a few hours on it, but I wanted to eliminate it as a problem). Per WW, blades statically balanced to "0.0 degrees" (on some special machine that measures this in a way I am not familiar).

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.

No backfiring. I am used to that sound. Dual electronic ignition. Had a good long talk with P-Mag people on what might be possible. But this EI configuration has been run on this airplane for HUNDREDS of hours on the prior 320 with NO issues.

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

I will be going through each of these again.
THANKS SO MUCH!
 
Issue: When I pull back on the throttle in flight there is a "shudder". Think reducing throttle for landing. Think adjusting throttle in formation.

James, just to be clear....the above has been consistently evident since the engine/prop combination was installed? Or did this behavior develop sometime later?
 
I have a dIfferent engine; RV7/M1B, composite (hartzell) prop - but have experienced a whorl at 900-1200 rpm if the engine is stimulated (read: landing bounce). I have rarely (or never, hard to remember everything) gotten it while flying. Throttle (RPM?) always stops it.BTW- I have lord mounts.

When it happens, there is a noticeable orbit of the spinner relative to the cowl. You might look and see if that is occurring to aid in your diagnosis. Especially since it sounds transient, not under load, and only when prop is aft loaded (pushed).
 
Hi James-----I'd like to tag onto Dan's question om whether this shudder popped up when the new combination was installed, or has developed after several hours of flight.
To me- a shudder at the very start of the combination would indicate something in the entire rotating assembly thats off alittle. May not show up as much under load, but by backing off the throttle is appears. Think rotating mass. Now i'm 'pretty sure' that Titan has all the internals balanced and matched, so I'd look at anything external. Back in the day we had an engine that would have a similar characteristic, and after really looks we had an alternator bracket that was cracked. The belt had alittle extra slack, and on power reduction, that slack made the long side of the belt vibrate.

IF the prop and internals are correct, it might be something to look at.

Tom
 
Dan,

I don't recall at the moment. Not sure if it was there all along or after going from FP to CS or when going from Carb to FI. See below ...

The original prop on the 340 was a 3-blade Catto. Not enough bite and too long to get another one built. RPM would turn over 2900!
The engine originally had a carburetor. But with the carb, I had too wide an EGT spread (over 300 degrees!)

Sooo... during this time I was mentally focussed elsewhere. Tried a ground adjustable WW and it worked fine on the test flight but I immediately knew that I really wanted CS. When I found that the Whirlwind CS was the same blades and had been tested on this engine, I got one.

Spent a lot of time trying to get the EGT spread fixed via carb adjustments but the carb manufacturer was not very cooperative with helping me solve the problem So I spoke with Airflow Performance and made it fuel injected. All the temps were then great.

By now, I am ready to fly and have fun. That's when I started flying with less timidity and noticed the problem as I recall.

I could TRY a FP prop again but going back to carb is a non-starter for me.

Just remembered one more thing. There seems to be a "bump" or "skip" every now and then when sitting on the ground idling. Not sure why, nor does AFP know why. Runs smooth though with throttle up. Climbs strong!
 
Thanks Tom.

Since I have removed and replaced the prop twice recently and loosened and tightened the alternator in each case, I don't THINK that is loose or broken.

Again, will look to see, again.
 
Follow-up

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.

To follow up on Dan's idea, I have been working with Whirlwind to explore this avenue. They have been a bit puzzled by this and their designer asked us to look into the hub. We are going to try a different hub. I have the prob back with the different (as in not my original) hub and will test that as soon as I get my ^&%^&^ leaking fuel tank fixed. I have "fixed" it four times, each time a NEW LEAK! Now seeking "professional help. :)

Hope this solves the "problem".
 
Just an idea to try. Normally before reducing the power lever for decent from cruise flight Lycoming advises richening the mixture. I used to wonder why. A few years of wondering had me as a passenger on a multi leg cross continent flight where I could carefully observe EGT's as the pilot simply eased the power lever back before starting a decent, and reducing power does lean the mix and raise EGT's instantly. Depending on where your A/F ratio is at and your timing/ ignition arrangement it might possibly explain the shaking(assuming it is not a prop /rpm /vibration issue)

VMMV
 
Thread drift..that &&^%$ Leaking Tank

James, I know that guy working on your tank..he is seeking the original builder to find out what he was thinking. The professional guy is very slow, but almost done. I caught a glimpse last week of what was going on.
 

Attachments

  • Tank.jpg
    Tank.jpg
    403.1 KB · Views: 202
WOW!

James, I know that guy working on your tank..he is seeking the original builder to find out what he was thinking. The professional guy is very slow, but almost done. I caught a glimpse last week of what was going on.

WOW!!!!!!!!!!

Thanks for the detective work.
Obviously, MAJOR surgery.
No wonder I kept running into more leaks.

I am going to owe the "tank surgeon" something special!! :)

To undrift the thread ... When I get the tank back and mounted, I will flight test with the replacement hub. If that goes well, I will balance everything, and hopefully get some performance data. Then, time to spruce up the ole bird a bit and get BACK to flying A LOT!

p.s. to VAF ... I did not build the tank originally, AND, these leaks developed over a couple of decades. So pay close attention to your use of "ProSeal" or "ChemSeal"!
 
There is an AD note on the venturi in the carburetor. If not replaced, or if either old or new part not seated, or mis-aligned, it will cause a shudder every time you go from the main jet to the idle circuit.

DAR Gary
 
There is an AD note on the venturi in the carburetor. If not replaced, or if either old or new part not seated, or mis-aligned, it will cause a shudder every time you go from the main jet to the idle circuit.

DAR Gary

THANKS!!

I think the AD probably happened after the reporting of my problem with the carburetor and then others having issues. I could not make progress with the manufacturer at the time so I changed over to fuel injection with the help of Don Rivera at Air Flow Performance. He is a short flight away from me.
 
Back
Top