SonexBuilders.net

Also for other builders as an update! Mark and I have been working together after the noted issues with the attachbars. We took my design, modified it slightly, and put together some new bars. These will come anodized and pretty like the original bars and Sonex will be releasing them very soon. I’m going to test a pair to ensure they operate the same as my design, then Sonex will be getting them out! Big thanks to Mark and John for their help and support!

Thanks for the update and video. Hopefully future 912 users will appreciate your contribution to a better mount.
Rusty

Thanks for the update!! I'm waiting for the updated mounts to continue with my build.

Good news!

As long as the new design only loads the isolators in compression and tension, this should be fine. However, bear in mind that prop traction too will load the isolators installed horizontally under the engine in shear, for which they are not designed. So this has to be taken into consideration the design of the new bars.

Thanks
Kai

Roger that!
That’s why in my design I did away with any horizontal bushings. That’s what caused the issue in the first place! It’s all just a bed mount now where the engine rests in a cradle with vertically positioned bushings and adapt perfectly to the original tube structure mount. The only change basically from the new ones, and the ones I designed is we got rid of the middle isolator bushings so there’s 4 sets instead of 6 sets.

Mark is shipping them out this week, next week I’ll install them and get some pictures on here sometime next week

In engineering, there is always a better way........

Why Rotax in the first place could not design their 900-series with a vertical flange mount for the isolators to sit horizontally, thus always loading them in compression/tension like Camit, Jab, UL, VW, LyCon, D-Motor, etc etc have done for ages, is a mystery. Of course Rotax has their bolt-on ring mount solving all issues, but it is heavy and shockingly expensive.

And, as many have discovered, once the ring mount is in place the issue with the water pump inlet elbow has to be dealt with, as the ring mount effectively blocks any possibility to hook up a hose. It forces the builder/installer to design and weld up an alumimium inlet elbow with a 35mm long neck.

So the question remains- which evil to choose? The engine has to be cooled and overloading the isolators must be avoided.

Preferences, preferences.........

Thanks
Kai

Hey guys,
So I received the new mounts, installed them, and I’ve been flying the new mounts a bit. I wanted to try them out for a while before I came back with any news. But the news is, they work fantastic. I don’t know if anyone has had a chance to look them up on the Sonex website, but they’re nearly identical to my originals. I hope those considering installing a Rotax are not detered from the previous mounts.
The only issue there might be is that I’m having too much fun flying this thing.
Next on the list, I’m designing toe brakes for the Sonex hydraulic brakes. But that’s for a different thread.
It’s been awesome talking to you guys, Ive enjoyed your ideas and insight.

Great!

I’m happy your work with Sonex solved this issue. Blueskies- Tailwinds!

I notice you fly behind a ground adjustable Warp Drive prop.

Could you elaborate about the rpm settings- wot static ground? And with this setting how much rpm does the engine pick up at wot cruise?

Thanks
Kai

Good to hear that it's working well, though I still like the ring mount better. I'm assuming the picture on their web site with the red anodized mounts installed is not your plane. The oil pickup should not be on the front of the engine on a tractor, and I'm hoping it was just an engine they had laying around to use for a picture. The prototype picture above it is likely yours, with the oil pickup where it should be.

Cheers,
Rusty (almost done with engine install)