Can you "Convert" my "Six Bolt"
drive hub to "Single Bolt"
we can, it is one of the Coolest Set-Ups you will ever
see. Please hang with us for the next couple of
pages, this is not a simple situation, there is a lot
to talk about.
There are only a couple
of reasons to be talking about doing a Single Bolt Conversion
to your existing engine. It is not about saving
money it is about problems, problems with vibration
or problems with the hassles of drilling and changing
We have all experienced
the hassles of messing around with the Six Bolt prop
mounting system, both at home in the shop and out at
the flying field on a nice pretty spring day.
This system works and would appear to be a heavy duty
set up, but in fact it is about the worst situation
possible and it is obvious if you really analyze the
The one main ingredient
that is missing in most six-bolt set-ups is the "Pilot"
to guide your prop and spinner on centerline of the
crankshaft. The 3-W engine has a six-bolt drive
hub and is the only engine on the market at this time
that has the pilot for proper mounting. The basic
rule of geometry is to get everything running in perfect
alignment so that it will not "Vibrate".
Six loose screws through
a hand-drilled prop are not going to make things line
up, it's only a "Fair" situation at best. The
next worst situation is an engine that uses a single
Hex Head Bolt to hold the prop on, it is a lot less
hassle but just about as bad. One loose fitting
bolt with no pilot guide for your prop or spinner is
not a good situation on its best day. We have
seen these types of drive systems cause problems that
even the user did not understand.
We are committed to "Precision
Machine Work" here at Tru-Turn, so our opinions about
engines and engine drive hubs are more than just an
opinion, they are the result of experience. We
machined the very first one-piece single bolt conversion
hub that was ever made, right here in 1986. It
was a result of trying to solve a problem with an A&M
six bolt drive that was causing major vibration.
The six bolts were not concentric to the hub and the
hub was not concentric to the crankshaft rotation.
This happened to be an engine that was to be used in
the "Tournament Of Champions" that year. The Single
Bolt Conversion worked great and the airplane wound
up in the Winners Circle.
The following sketch will
show you the single bolt and how it is mounted.
It is an addition to your engine that requires some
consideration due to the fact that these conversions
can run from $ 59.95 up to several hundred dollars depending
on your situation. The single bolt conversion
will not run true if it is mounted on something that
is running out, so mounting it becomes "Very Important".
HERE FOR FULL SIZE DRAWING.
Some engines that use the
six-bolt or hex bolt system have a considerable amount
of run-out as mounted from the factory. They do
not hold close tolerances and they do not machine the
drive hub after it is mounted to the crankshaft, therefore
run-out occurs and vibration becomes a factor to the
overall well being of your airplane. When we machine
your engine drive hub and mount a "Single Bolt Conversion
Hub" on it, all of these things are no longer a factor.
You have a true running hub, a "Pilot" diameter to mount
your prop and spinner on and you do not have all of
the hassles of the multi-bolt drive.
The only bad news about
this conversion is that in some cases you will have
to send us your engine. The drive hub must be
prepared for the conversion hub, mainly because most
drive hubs do not have a way to mount the hub or they
do not run "Tru" enough. Most engines run around
$ 45.00 for machine work and the conversion hubs run
$ 59.95 for the small 3/8" type up to $ 99.95 for the
big, extra long ½" hubs for the big engines. They
are available in short or long shaft and in 10mm diameter
as well as the more popular 3/8", it all depends on
what you are trying to do and what you are trying to
do it with.
You will see these conversions
on "Unlimited Racing Planes", I.M.A.C. Planes, T.O.C.
planes as well as just every day sport flyer's airplanes.
Sometimes you will see single bolt conversion hubs made
by "Other" companies, but you will never see any other
brand made as well as a Tru-Turn Hub. Tru-Turn
Hubs are machined from 17-4 PH Stainless Steel in the
H-1075 Heat-Treated condition for maximum strength,
absolute concentricity and corrosion resistance for
use around any type of fuel or cleaner. They are
100% C.N.C. machined to exacting tolerances of
less than .001 inch, unlike other "Look-Alikes".
You will not find better
"Quality" or "Service" anywhere! Just give us a
call and we will walk you through the details, give
you a firm price, and get you going quickly.
If you have more questions
or do not see what you are looking for, just "Call"
or "E-Mail" us and we will do everything we can
to help you.
for shopping the TRU-TURN Website.