I have an idea for you Scott.
There is a water jet company in 1500 Airway Circle, New Smyrna Beach
FL. 32168 | 386-424-7333 <
tel:386-424-7333
I have some drawings of a steel coupling that can be made out of
water jet cut steel parts.
Then you will need to find a local tig welder to weld it up.
I have some of the parts. The inner plate that bolts to the counter
weight and the outer ring cut from six inch tubing.
$50 plus mailing.
Use part of Tracy's torque isolator to adapt this to Tracy's PSRU
input shaft. Drill out the rivets and bolt it to the steel output
front plate.
Paul Lamar
Very interesting! I can query the water jet shop, and will order
these parts if the shop can make the rest. No problem with the
welder.
How thick is the metal?
Do you intend for an outer ring to be cut into the small curved
shapes, or make these from scratch? I guess they can be flat
instead of curved?
I also assume the 1.78” is the height of each component, so the
total thickness would be about 2”? I will study my redrive to look
for areas of potential interference.
Please ignore the curved questions of my last post, sorry. Some of
the latter images didn’t display the first time. I see the
connecting elements are square.
Thanks!
Scott Gettings
.050 to .150. Some of the stuff is .083. You make it out of what
you can find :-) The six inch tubing is about .150 wall.
The total thickness is about 1.8 inches. Nothing about this is
critical. One inches would work if your not shooting for 500 HP.
Ignore those square pictures. The latest are triangular or wedge
shaped. The square ones bottom out corner to corner. We discovered
that when we built the TTC coupling.
If I get a little more interest in this I wall make a tool that
bends the wedges in a hydraulic press. Saves a bit of welding. I have
built tools like that in the past. That would pay off as the same
design can be used in new gear boxes. We already used one of these
that was similar in a 3 rotor.
I have not heard back from Kevin so if Kevin finds an NC shop that
can make them out of billet at reasonable cost that would be more
accurate.
In any event once this is welded up it would be wise to balance it
between parallel bars. If your gear box is off the engine please
tell me the diameter of the input spline adapter Tracy is using. The
one with all the rivets. That will control the diameter of the
forward plate.
Paul Lamar
Paul,
My welder can assemble these small steel parts, but is not highly
confident of the precise alignment and balance of the end product.
It looks like some other options are evolving, so I’ll keep this
one on hold.
My gearbox is on the engine, but if you need the exact shaft
diameter soon, I will be happy to pull the it and measure the shaft.
Other measurements that might be helpful: distance from front edge of
flex plate gear to rear of engine block: 1 5/16” distance from front
of Tracy’s adapter plate to engine block (the total “open” area
between the engine and adapter): 3 1/8” distance from front of
Tracy’s adapter plate to rear face of his riveted spline adapter: 1
1/4” the front of the spline adapter appears very close to the rear
edge of the flex plate ring gear.
It appears that the total thickness of a new coupler (for Tracy’s
RD) would need to be the exact distance from the rear face of the
bolted area of the flex plate to the rear of its ring gear, which is
the plane of the front of the riveted part of the spline adapter.
This would maintain the dimensions for the thrust bearings. A
coupler that is more thick than this would move the rest of the RD to
the rear, requiring alteration of the existing spacers (the 3 1/8”
distance). A thinner coupler could be managed with thrust bearing
washers.
Scott Gettings
I just happened to have one. The OD of the part in question is 6.188.
The long part that sticks away from the engine 1.158 long.
The idea is to turn it around and put the long part inside the
coupling. We worked this out years ago :-) 3D's 5 and six show this
config.
That Ford part raw weighs 3 pounds. There is unnecessary meat on both
sides that I can be cut off if you send me yours. That will give you
plenty of room and save a bit of weight. Some of the spline part can
be cut off as well. 1.25 inches of spline would be plenty.
Jean is down the road from you in Pompano Beach and he might do it
for you. He has a lathe and a mill. He will need one sooner or later
:-)
Here are a few pictures.
Paul Lamar
Scott, I'll check the dimensions on my RV4. It still has Tracy's
coupling so I will need to change that anyway. I was going to use it
to flight test my new gear box design.
Here are a couple of pictures about what my coupling looks like
now.
Here is what it might cost if you had the coupling NC Milled In US
dollars from the Internet.
Setup/Programming - 40
Fixturing - 60
Engineering Services - 40
Machining Time Per Part - 60
Inspection/Deburr - 40
Test Part Machining - 60
BS Time - 40
Let me know what you are leaning towards so I won't have to take the
gear box off my RV4 just yet :-)
---------------------------------------------------------------------
OK Scott I got motivated. Lately I have been suffering from lack of
motivation :-)
The max thickness of the coupling is 2.25 inches thick from the
surface of the flex plate to the back of Tracy's spline adapter. That
is a cut down stock ford transmission part. I cut mine down a bit
more and saved .5 pound. I turned it around and put the long side
inside the coupling.
This gear box has about 30 flight hours on it so far.
Here are all the pictures. A lot of work :-)
Paul Lamar
This looks like quite a bit of work!! Most of it is well beyond my
level of expertise, but with detailed drawings and instructions, and
Paul's help, it may be achievable. Is the updated coupler design the
primary deciding factor at this point in time?
Scott Gettings
I am not sure what you mean by that but it works as it has been
flown on a 3 rotor and the TTC.
I did a lot of work taking mine apart this morning to check the
max length. Here are six pictures taken this morning.
Paul Lamar
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