Classic IV with Rotax 912 iS Sport

[jrevens]

What a great accomplishment... congratulations!

[ofergd]

It wasn't so simple. We thought we could install the cooling system inside the cowling like the installation in the SS7. we even designed and manufactured a stainless steel duct around the muffler, but we have a round bumped cowl and the flow inside the cowl was not enough. We got too high temperatures while standing and taxiing. So, we took out the coolant heat-exchanger and put it under the fuselage (didn't install the scoop yet) and installed the oil radiator in the front, under the prop. Now the temps are high, but under control. We will probably need a larger radiator for the coolant or oil or both (suggestions).

[HighWing]

Great Project. Reminds me of my build. I also moved the engine forward, but only 2-1/2 inches. The best part of that for me was the ability to mount the oil tank lower on the side of the engine to prevent back flow from the high and behind the engine mounted tank to the crank case sump. Regarding the cooling. The typical 912 installation over the years showed excessive cooling from the oil cooler and adequate from the coolant radiator. My suggestion would be to enlarge only the coolant radiator. That is using the 912 UL and the 912 ULS, however. Not sure if the IS would produce more heat while running. Glad to see another IV ready to fly. As others have mentioned, keep us posted on further progress and flights.

[Av8r3400]

I would really be interested in some more photos of your engine mount.

I very much like the fact you used the Rotax "horse collar" in your design. I would like to do the same with my plane in the future. Where/how did you locate the oil tank?

[ofergd]

Not sure if the IS would produce more heat while running.

The iS is running lean of peak most of the time, therefore it is running hotter than the standard ULS.
Will consider you suggestion.

[ofergd]

A few pictures of the installation.

[HighWing]

I made up my own "horse Collar" and after positioning the engine where I wanted it closed the gap with 4130. i made molds of Delrin and poured isolaters using a two part Urethane rubber. The oil tank is painted because I wanted to hide the hammered modification (near bottom) needed to give the quarter inch clearance I wanted between tank and cowl. Another thing that worked into the mount was the fittings that were used to mount the ignition modules.

[ofergd]

The "horse collar" supplied by Rotax was part of the engine we got so we didn't have to make our own. The iS is very "crowded" and hard to access all the necessary bolts for connecting and removing of the horse collar from the engine.
We kept the engine in the same place as it was designed and then designed the engine mount. We noticed that two of the members (1 on each side) were interfering with the foot-wells, so, we "pulled" the engine forward until the member was clear of the foot-well. Only then we started to cut the steel tubing.
If you put the engine a bit higher, you can put the engine closer to the fire wall.