My Rotax Mount for a Onex

[gcm52]

I just mounted my Rotax 912ULS onto my Onex. The mount was designed by me based on other mounts I have seen, I created a jig based on an EAA video, cut the tubing using a coping cut program on the web, and had an FAA certified welder weld it up. Everything fits well. Photos attached, also added a photo of my toe brakes. If you are going to buy a Rotax engine, I recommend you sign up for the Rotax service tech course. This is a two day course where you learn all the ins and outs of Rotax engines. After you complete the course, you can get a discount on Rotax products, so this pays when it comes time to buy the engine and all the accessories. I took my course at Leading Edge Air Foils in Wisconsin and it was great. People came from as far away as Oregon to take this class.

[Marrahm]

Well done! the factory mount looks like a bed mount — is there a benefit of one style over the other for this application?

Mike
Sonex 1713B (and leaning towards Rotax when the day comes..)

[lgsievila]

Hi George,
Your install looks good and I believe you will be very happy with your Onex with that engine. Just curious as to how far you moved the engine forwar for CG as your Rotax is lighter than the AeroVee. I had to add 7 inches to the mount when I went to a CAMit 2200 from an AeroVee. Looking forward to hearing your performance numbers when you get flying.

[WaiexN143NM]

Hi George,
Wow! Bravo! Looks great that mount and the toe brakes set up on your onex . Yep the onex is just begging for more engine options. I’m sure Sonex could sell a lot more onex kits with some other engine options, UL260, rotax 912, jab 2200. At least a factory mount. The builder would have to due their own fwf from there.
Keep us updated.

WaiexN143NM
Michael

[Waiex 49]

Nicely designed and executed Rotax installation!

I think you will be very happy with this engine and airframe match up.

Please post more updates as you move forward with your project!

Fly safe,

Don Bowen
N49YX
Outlaw Viking Waiex

[gcm52]

Regarding the bed mount versus the ring mount, a Rotax mechanic explained the benefits of the ring mount to me a long time ago and I can’t remember what he said, but the ring mount is considered a bit better than the bed mount. Even so, due to lower cost (the ring mount for the Rotax is $700) I initially was going to use the Sonex bed mounts and more or less adapt the Sonex engine mount to the Onex. I called Sonex to see if I could look at one of their Rotax engine mounts (I live just an hour away from the factory) but they make them to order and didn’t have any in stock. I did order the Sonex rail mounts that bolt to the side of the engine but then discovered that these mounts conflict with the new Rotax factory exhaust system. The Sonex mounts might be compatible with the old Rotax exhaust system, but Rotax now offers this new system which is fully welded up and requires less work than the old (less expensive) exhaust system that they still offer. It would not have been a big deal to weld a 1” extension into two of the rear exhaust pipes of the new system to get it to fit but at that point I thought the universe was trying to tell me to go to a ring mount so I bit the bullet and ordered the ring mount from Rotax and went that route. By the way my Sonex rail mounts are for sale in the classified section here.
As far as the CG considerations for the Rotax, I did move the engine forward 7 inches.
If anyone is considering making their own mount, this program is very helpful in cutting the tubing to fit all the weird angles:

http://www.metalgeek.com/static/cope.pcgi

The program outputs a paper template that you tape on the tube that shows you how to cut it to get the correct angle. I cut the tubing with an angle grinder.

I also found a video on the EAA site that shows how to jig the engine mount. The attached photo shows the jig. The threaded rod set-up allows very minute adjustments to the mount, and is strong enough for a one-off welding job.

I had an 80 horse Rotax 912UL engine in a Zenith 701, and I grew quite fond of that engine. It gave me zero problems, just flew and flew.

[Concorde]

Very nice .
What prop are you going to use ?

[gcm52]

Very nice .
What prop are you going to use ?

I am leaning toward a Sensenich three blade ground adjustable. THey have a "pin indexing" mechanism for setting pitch that really looks neat. What prop are you using? Are you flying? What kind of performance are you seeing? By the way I increased the length of my nose strut by 3 inches to accommodate a bigger diameter prop for the Rotax. My understanding is that anything below a 62" prop creates cavitation on the takeoff roll.

[roberttmoore]

George,

Bob Moore here in eastern Washington state. I have a TD Onex with the aerovee and a prince prop. I recently purchased a used 912s and a portion of the (engine side) ring mount. I am setting out to install the Rotax in my Onex, along with a Dynon D180 superbright. I could make up a bed mount using the Sonex rubbers and the mounting bars, but am leaning toward the rear ring mount with Lord or Berry or rotax rubber. If you are flying yet, how is it working out? getting off the ground, climb, cruise/rpm. WOT/speed/rpm,etc. If willing to share your email, that would be great. I will probably have a million questions (well.....maybe only 100,000 or so....). I really don't want to committ too far in without some guidence from "those that have gone before".

On a somewhat related matter, I also have a fairly new 912 with a big bore kit. I am mounting it on a CH750 using the Zenith FWF kit for the Rotax, that includes a bed mount. Hopefully less challenging than the Onex, more just plug/bolt and play. I am partners on a Searey, that has the 912s and a bed mount, so have something similar to study during the adventure.

My email is... bobandlindamoore1@msn.com

Thanks in advance for any valuable information.

[Thermalflyer]

Hi, George.
I have a one X and a rotax 912uls. I would like to know how your mount worked out CG wise.
Would you share any info dimensions wise in the location of the mounting for the trigear.
Any photos would be very helpful.

Thanks

Ray Wilhelm
rwilhelm25@gmail.com