Blll , Lynn , Le Roux and All,

      All very valid concerns about engine twist and bending moment............To my knowledge "Mistral" did not use .500 inch (12.7 mm) studs in their 20B engines and to my knowledge

the "Mistral" side housings were still cast iron (heavy).............A purpose built 20B for aircraft in my opinion should have all alloy housings and  .500 inch studs...........

     Think about this hypothetical situation..............You have an all alloy 20B boosted to 70 inches map (about 1500 dyno hp) and tricked out with all the racing options available in a

drag race car.............It is supported from a center housing (as a stock engine)............Then at about 9000 rpm you drop the clutch............What kind of bending and  torsional loads do

you think this engine endures ??...........In Rotary racing circles this happens all the time with amazing reliability...............Now think about an all alloy 20B (boosted or NA) in an aircraft

driving only a propeller (no shock loads) built to racing standards as a NA (no boost and approx 350 hp) and flown between 6000 to 7000 rpm or boosted to normalize only............

    Again the same engine (running at 6000 to 7000 rpm) boosted just enough to dyno about 800 hp (piece of cake for a 20B)...........Of course this is only my opinion and you know what

opinions are worth..............I understand that most of this group are interested in the 13BREW or RX8 Renesis engines but you have to admit I have made the forum lively lately !!..........

 

   As things progress or digress I will let the forum know until told to stop............Many thanks to Charlie for resizing my photos for the group ( I am better with a wrench in my hands)........

Best Regards,

Kelly Troyer 

     

On Mon, Aug 3, 2020 at 4:26 PM lehanover lehanover@aol.com <flyrotary@lancaironline.net> wrote:

The bending loads are carried for the most part by the upper tension bolts. The studded engines are using the tight fitting studs to manage torsional loads. In high power street and drag race engines it was not at all uncommon to fail an alignment dowel (shear it off) or break out and alignment hole in the iron. Very messy as the top runs have oil pressure. The studs provide more clamping pressure and help keep the rotor housings in the correct shape. The housing walls tend to move away from the rotor face during combustion. If you take apart an old engine you often find that the rotor housings have a hint of black death (similar to black death on the sides of pistons) on the clamping surface near the spark plugs. This is the housing moving on the cast iron. Early case bolts were necked down between bolt head and the threads. Later bolts are not...........more clamping pressure.   The case bolts used in high output engines fit snugly in the holes. So the holes are reamed with the case bolted up and torqued. One at a time....so is costly to have done. It is also a source of add HP and less wear. Notice that even later 13-Bs have the engine mounts on the center iron so as to reduce engine twisting. ......Lynn E Hanover   

In a message dated 8/3/2020 4:02:49 PM Eastern Standard Time, flyrotary@lancaironline.net writes:

Bill : The bending moment and axial loads you mentioned. Could it possible be - why some of the early design  allumnium casted sumps, of the Mistral 3 rotary engines developed cracks ? as i remembered that the bed type mount for the rotary ( pusher type config.) the thicker sump and plate, has a lot to do with these loads and stiffen the rotars and irons as a solid unit, as well the bigger diameter tension bolts and “dowls”
It was just crossing my mind, and i have no previous experience in these loads and type of mounts as well as the casted sumps.

The torque loads of the prop and all ads up.

Included : cut out of the article Mistral Magic

Could the loads be part of the sump problem in these type of mounts? i don’t know.

Cracked Sump

“I did have a couple of teething problems; the most important one was a crack in the aluminum-cast engine sump that I found during taxi tests. Mistral reacted in their usual fashion. After getting details, they confirmed they had a crack in the same area on one of the sumps they tested. They designed a reinforced sump, but never got a repeat crack on the other sumps, so none of the new models were made. I was offered a temporary replacement until the new sumps would be produced to replace all present sumps. I decided to wait, and got my new sump within two months—and a Mistral engineer came and installed it for me.”

Sent from my iPhone

Le Roux Breytenbach

On 03 Aug 2020, at 19:34, William Jepson wrjjrs@gmail.com <flyrotary@lancaironline.net> wrote:

Charlie, and everyone rotary,

I can see the desire to put a rotary in a similar mount to a standard aircraft engine. But I want to remind everyone that a Mazda wankel in its automotive layout doesn’t work well as the stack of plates and housings isn’t set up to handle the bending moment. In Mazda’s racing engines they added plates to enable them to hang the engine from one end. They still used cradle mounts. The Lyc engine shown in the example has 2 crankcase halves solid front to rear where the mounts are. If you don’t plan to build the rotary with some modifications for axial stiffness and housing location it isn’t a good idea to hang it from one of the end plates.

Bill Jepson

On Mon, Aug 3, 2020 at 5:45 AM Charlie England ceengland7@gmail.com <flyrotary@lancaironline.net> wrote:

On Mon, Aug 3, 2020 at 7:40 AM Charlie England <ceengland7@gmail.com> wrote:

There are 8 pics in this series. My image resizer program got them down to around 110-140 KB each, so they'll need to come in 8 separate emails.