This Rhino 3D  layout is very useful as it can save months of trial
an error. Prior to my doing this people would spend up a year laying
out the parts in the cowl and then they found a serious problem
and had to start over. If you don't have Rhino or the year required
to learn how to use it you can cut a bunch of foam mock-ups
and mount them inside the cowl if you have one.

The rules of motor mount design.

A: Don't apply loads to motor mount tubes except at the very ends.
In other words do not place any bending loads on motor mount tubes.
This might work for a while but due to vibration the tube could
develop cracks or fail completely.

B: For all intake and exhaust plumbing use off the shelf tube bends.

Now the problem is adapting this gear box to the power output end of the Wankel engine. Since the starter ring gear is usually also on the power output end one must find a way to get the power and torque beyond the starter ring gear. It is desirable to keep the overall length of the Wankel aircraft engine installation below about 36 inches over all as that is roughly the length from the firewall to prop shaft on most light aircraft. In other words the length of the engine cowling. One could use a stock high pressure die-cast bell housings as most rotaries use to adapt to an automotive transmission. Therefore it is best to put some of the gear box inside the bell housing. A sand cast custom bell housing was tried but proved to be unnecessarily heavy due to sand casting minimum thickness limitations.

Another way of doing it is use long bolts and spacer block to locate an adapter plate about 3 inches away from the front end housing of the Wankel. This idea was widely used starting in about 1997.

Tracy did this in about 1997 and it has been used ever since. I added the motor mounts to
this plate about 1998 or 2000  as it was located more or less at the power pack CG.
You can get fancy if you have a lot of money  and use a NC Mill to pocket it or
just use a hole saw to save weight.

Here is the latest BD4 layout. Clearing the intercooler  plumbing was a major problem
but this engine package will make any HP up to 500 HP on gasoline. It is cannon
prof due the combination of its basic robust  mechanical structure and the use of silicon nitride
apex seals.

One cannot not buy a certified airplane under a gross weight of 3000 pounds that will
come any where near the performance of a BD 4 with a rotary. Not only that the engine
will have unlimited life. The 500 certified Austro rotaries flying have no TBO.

Bob White crashed this rotary powered BD4 with a bad landing. It tore all the blades off a carbon
fiber prop. The lower motor mounts tubes were .75 inches in diameter so we went
up to one inch on these dwgs. No other damage to the motor mount system occurred.
It bent the BD4 fuse and wiped off the landing gear.

Paul Lamar

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