Rotax ring mount

[Kai]

Oki,

Duly noted!

Then, if you eventually might decide on a ring mount, as far as I can see your only option is as you say to get in touch with a good welder who can come up with a completely new engine mount for the airframe.

The finished product would be looking something like the mount attached to the airframe shown in enclosed picture.

[Skippydiesel]

Now that is truly awesome!!!!!!

[AlexZ]

The engine mounting points on the 3300 mount are 59 mm more aft then the Aerovee. To put the prop flange on the same position 88 mm is needed. The 29 mm more forward, with the original ring mount, shouldn't be a big problem, because the Rotax is lighter then an Aerovee. And it's already done.

[Skippydiesel]

Hi Alex,

In the stunning installation above, it looks like the frame (that the ring mount is attached to) has more than enough capacity to be reduced/extended as required, to get the prop hub in just the right position.

Without measuring and from recent memory , the rear of the above engine looks to be further (29mm?) from the firewall than my Sonex/Rotax adapter installation.

[Kai]

Hi Alex,

In the stunning installation above, it looks like the frame (that the ring mount is attached to) has more than enough capacity to be reduced/extended as required, to get the prop hub in just the right position.

Without measuring and from recent memory , the rear of the above engine looks to be further (29mm?) from the firewall than my Sonex/Rotax adapter installation.

Looks can be misleading. In order to make room for the plenum cannister and intake runners, Edge has to reposition ignition modules, coils, and the coolant filler neck. This could make it difficuilt to make a direct dimensional comparison with an unrefined R912.

I´ve had a short conversation with the guy who welded up this frame. It started with him purchasing a second hand Sonex A taildragger serial #0772, originally built as an EXP class project in the US. When he got his hands on it came with a disastrous low power, undercooled gen.1 Jab 22A. Basis for the welding jig were the airframe attach brackets and the firewall as supplied by Sonex, and to get the prop flange at the exact location Sonex suggests, this Jab 22A.

He wisely decided to go for a 123HP EP915ECI pluss original Rotax ring mount, original Rotax rubber vibration isolators and all, and the frame was welded up. Then disaster struck- a female became a large part of the picture: the divorce proceedings were probably nasty. He had to sell.

The new owners bolted everything together. After careful measurments with laser, it was found that the engine prop flange was smack on where Sonex at that time (around 2019 or so, give or take a few) wanted it.

[Skippydiesel]

I take your point(s) / understand about the adjustments that needed to made to accomodate a 123HP EP915ECI - Not sure that quite so much would be needed for a standard 912ULS, after all the ring mount is designed for it.

Unfortunatly divorce does not seem to be in my foreseeable future - such is life!

[AlexZ]

The Jab 2200 mount is unusable because it's 76 mm longer then the Aerovee mount. That's why a complete new mount was made.
Designing a new mount isn't too much work based on the picture. I did the same for my other project. https://eaabuilderslog.org/?blprojentry&proj=8FBT6WagN&e=8FBV2luMI&listcat=&sid= But then setting up a welding jig, making all the tubes fit and welding takes a lot of time. For the few Sonexes flying in Europe it makes no sense to set up a 'production' run.The US market is bigger, but then shipping becomes a big cost factor.

[Skippydiesel]

I'm speculating:

Longer should not be a problem, as can always be shortened and any removed pipe reused.

From what others have said , in this conversation, it's the not so much the Jab 2200/3300 engine frame itself, as the firewall/ undercarriage frame - the horizontal square section tube in particular - as a foundation for the ring mount adapter.

I am hoping that at some stage some clever person will produce drawings with dimensions/angles so that dum chums like myself can cut (& get someone else) to weld.

The bottom image in your, "other project" looks a tad odd.