New Subject, Does anyone have a dimension-ed drawing for a 3:1 reduction box
modeled on Tracy's Box?
Milo
This is what I have so far.
Paul Lamar
I measured mine up for CAD drawings before I assembled it, but with the
holidays I haven't had time to draw it. I will get to it shortly.
Kevin Alderman
Kevin, would appreciate a copy. I think it is time to do a 3:1 drive. Would
like suggestions from one and all on the appropriate gears by part number if
possible. Also design concepts as well, like integration with the standard
bell housings to keep the costs down.
milo
If you build it like this you can use a relatively cheap constant speed
hydraulic prop.
I forget the attachments.
Paul Lamar
I do that also. I thought they were grey hairs overcoming me, but there is
some evidence they may be blonde:-))).
Dale Davies
Paul, Jean Prudhomme has a PSRU similar to your attachment drawn up in Rhino
and made the casting patterns for it. I don't know the current status but
perhaps he will let us know.
george grimes
George, do you know what the part numbers for the bearings and the material
and heat treat for the shaft
Milo
If you copy the Lycoming crank shaft dims you can use the Lycoming shell bearing
and front stretch over oil seal.
That is what I would do. It is a proven design. Some times you can make the
smallest of changes in a design and run into all sorts of unforeseen problems.
Paul Lamar
Paul,
The real expensive element is the steel shaft, did you price
out a forging blank for the 3:1 setup?.
I have an idea for segmenting that shaft so that it could be
machined out of 4140 stock, but first we have to deal with the bending loads.
Milo
Contact a Lycomming overhaul shop and buy a cracked crank.
They generally crack is the journal fillets.
Cut at the first cheek and tig weld on a flange for the planet carrier.
All the Ross boxes were tig welded flanges for the planet carriers.
That is a low stress area of the crank for our application.
Not a low stress area for a piston engine.
Just 600 foot pounds of torque. No bending.
No prop gyro bending loads that affect the prop flange end.
Or you can do something like this bunch of screws bolt on flanges.
Paul Lamar
THANKS! Paul, that helps quite a bit.
Does anyone have an appropriate sized Lyc. shell bearing good for
230hp kicking around the shop that they can spare?
milo
Milo, As far as I remember Jean got a price of around $300 for a piece of
4140 billet. He was going to rough out the machining to some point on the
CNC G-code, skip down to the next area and rough out etc. then delete the
code that went between. The idea is to reduce the CNC machining time.
The bearings are larger diameter than Lycoming as shown on his drawing. I
recall 3.25 diameter and from a big block automotive engine from Chrysler or
GM. Several main bearing shells, one of which was the thrust bearing. Oil
drain back between the shell locations and one of them isolated the constant
speed prop oil which could be at a pressure different than the engine oil
pressure. I remember Jean had some castings poured and you might get the
guinni pig discount on a pair of unmachined castings I have also designed a
PSRU but heavier than the one Jean has. Same diameter shaft but sperical
roller bearing at the prop flange and timken bearings at the rear of the
shaft and input shaft.There is also one journal bearing that floats on the
prop shaft which is restrained from rotation by the feed tube that passes
through to the outside of the housing. My patterns are about 90% done and
the bearings are in storage. These patterns as with the engine patterns
need a little detail sanding and surface sealing. I use a borg warner 4407
planetary from the transfer case of the F-350 truck with a ratio of 2.64:1
which has a torque capacity three times as high as the F4OD planetary which
is 2.85:1 I would not recommend my PSRU to anyone else. It is a one-off for
a turbocharged 4-rotor designed for HP capacity rather than minimum
weight.The roller bearings added 8 pounds of weight, required a larger
diameter casting for another 6 pounds, An integral bell housing/oil tank
which added length (and eliminated the prop shaft spacer) and added
considerable weight compared to Tracy's spacers.
The other planet set in that transmission is I believe 3.17 :1 but I
would have to verify the ratio These ratios are all with the ring gear fixed
and drive through the planetary carrier. The rotation is the same direction
as the input shaft. When driving fro Just remember vibration problems could be more severe with metal props than
wi Regarding the lack of vibration with the rotary and metal props as per quote
below, what happens when operating inadvertently on 1 rotor (for instance if
an apex seal went bad, will a metal prop make things worse than wood or
composite? I ask because (i believe) under Canadian registration (which im
contemplating later down the line) if you fly IFR you have to have a metal
prop.
Alex Molteno
The kind of vibration I was talking about was the kind that cause
a bending mode in the metal blade that sometimes cause the tips to break
off. Common in AC piston engines.
In the case of one rotor not firing the torsional resonant
system would be little affected as the forcing function
is half as strong. I have heard two rotor engines running
on one rotor and the noise is definitely changed but there were
no noticeably consequences. The balance of the engine stays
the same. In theory the resonant frequency is lowered due
to the higher rotational mass of the metal prop.
BTW one bad apex seal does not cause the rotor to completely
stop firing. It will miss for sure. If you could get it started
the rotary will run at high RPM with no seals.
Paul Lamar
Another good reason for going with the rotary,that's good news.
Thanks Paul, I received the cooling book yesterday when i arrived back in FL
Alex
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