Today's Message Index:
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1. 05:47 AM - Re: Nose gear shimmy (johngoodman)
2. 07:24 AM - Re: Nose gear shimmy (bill.peyton)
3. 08:08 AM - Re: Re: Nose gear shimmy (Kelly McMullen)
Message 1
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| Subject: | Re: Nose gear shimmy |
I never had any nose shimmy with my RV-10 for 5 years. Then, my new partners wanted
to change from a
Corvette engine to a Lycoming 540. We used a new engine mount, and a new engine.
Everything firewall forward was new. The shimmy started on the first flight. I
am skeptical of assumptions that it's something to do
with the wheel or the mount. I'm leaning toward the 6 cylinder engine, versus
a 4 or 8 (like my old corvette LS1).
Six cylinder engines are naturally unbalanced. I know the jury is still out on
this one, but it seems to be just an RV-10 problem.
John
PS: sorry for the multiple paragraphs, but big photos make looooong lines of text...
--------
#40572 Phase One complete in 2011
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=473121#473121
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| Subject: | Re: Nose gear shimmy |
First, you need to size your photos smaller prior to posting.
Several things can cause the nose wheel shimmy. Usually the friction nut needs
to be retightened to take up the slack in the belleville washers. It's tough
to over tighten this nut.
The second is the axle assembly. If you are using the matco axle, confirm the
the wheel is centered in the fork assembly. My original bushings were machines
incorrectly and my wheel was not centered. If you are not using the matco axle,
you need to order it.
Third, the tire provided with the kit is junk and should be replaced with quality
tire such as a Goodyear flight custom or Michelin. My kit provided tire was
way out of round.
The VA144 bushing that you are seeing play in should be installed in such a way
that it protrudes from the edge of the gear leg assembly. When you tighten the
nut you are tightening against the VA144 bushing. As I recall, washers can
be used to take up any play as require. It's been a while, but I recall having
to machine a new bushing to get rid of the slop in the gear leg. I'm not in
front of the drawings at the moment, so excuse me for lack of assembly part numbers.
I have over 700 hours on my 10, and I still get some shimmy, or more of an up down
motion, after it sits for a week. It will usually disappear after a long
taxi. It occurs around 14 kts.
--------
Bill
WA0SYV
Aviation Partners, LLC
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=473127#473127
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| Subject: | Re: Nose gear shimmy |
Don't know where you got the idea that a 6 cylinder is unbalanced. Six
cylinder engines in the 3 most common configurations are very smooth.
That would be flat six, V6, and straight 6. I've driven all 3 in auto
applications---Ford straight six from the 50s, Corvair flat 6, and a GM
V-6 in a Jeep. (BMW straight and V-6s are some of the smoothest engines
around). Big 4 cyl car engines are either very rough (Pontiac Tempest
194) or have balance shafts.
Lycoming perhaps doesn't use a cam design to be as smooth at low speed
as it could be. Continental 6 cylinders are very smooth, if somewhat
heavy. Six cylinder engines fire every 120 degrees for a very smooth
output. Four cylinders fire either every 90 or 180 degrees and for all
but the under 2 liter sizes need a balance shaft to smooth them out.
V-8s fire every 90 degrees and have enough cylinders to create balance
the 4s do not have.
OTOH, Lycoming 4 cylinder engines are about as unbalanced as it gets.
Big six cylinder engines like the 540 and the big Continentals run
smoother with a 3 blade prop than 2 blade..but I am not suggesting a 3
blade would make any difference in shimmy. 3 blades are a PITA for
removing the lower cowling, and most cost 3-5 kts in cruise, while
climbing better than 2 blade.
There likely are some explanations in the Lycoming Dynafocal engine
mounts and how that interacts with the nose gear, but it isn't the
engine smoothness.
On 9/24/2017 5:46 AM, johngoodman wrote:
>
> I never had any nose shimmy with my RV-10 for 5 years. Then, my new partners
wanted to change from a
> Corvette engine to a Lycoming 540. We used a new engine mount, and a new engine.
> Everything firewall forward was new. The shimmy started on the first flight.
I am skeptical of assumptions that it's something to do
> with the wheel or the mount. I'm leaning toward the 6 cylinder engine, versus
a 4 or 8 (like my old corvette LS1).
> Six cylinder engines are naturally unbalanced. I know the jury is still out on
this one, but it seems to be just an RV-10 problem.
> John
> PS: sorry for the multiple paragraphs, but big photos make looooong lines of
text...
>
> --------
> #40572 Phase One complete in 2011
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=473121#473121
>
>
>
>
>
>
>
>
>
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