Sonex/Rotax Engine Bed

[Skippydiesel]

Have checked out the feasibility of installing two anti frame twist rods - seems possible.

The plan at this stage, is to fit, 2 pieces of aluminium angle(20 x 20 x 2mm), 500 & 560 mm long, to each side of the frame,. Fitted from high, close to firewall, down to near tip of Aerovee frame.

The angle will be attached to the frame using heavy duty aviation (rubber saddle) "P" clamps, sized to suit the frame tube (no cutting/welding/damage to frame).

Before fitting, I will lightly jack the frame up, to neutralise the weight of the engine.

The hope is that the additional supports will be tight (no slop). When the movement of the engine tries to twist/flex the frame, the supports will resist.

Should I have any concerns?

[Skippydiesel]

The addition of engine frame stiffening struts seems to have had no effect.

The struts are not ideally located for best effect, due to clearance considerations.

I marked the position of each end of struts P clamp, so that if they moved I would be able to see this. No indication of movement

[Skippydiesel]

FYI:

Have just received an Email from Sonex - " ...a new ring style engine mount (Rotax) is being thought about for the new High Wing..............the High Wing is
a B-Model type"

So owners of Legacy (A) aircraft, may not see a Sonex produced Rotax engine mount, any time soon.

Very disappointed.

[BobDz]

FYI:

Have just received an Email from Sonex - " ...a new ring style engine mount (Rotax) is being thought about for the new High Wing..............the High Wing is
a B-Model type"

So owners of Legacy (A) aircraft, may not see a Sonex produced Rotax engine mount, any time soon.

Very disappointed.

How possible, and or difficult would it be to make one? I'm curious about how engine mounts are designed. Specifically, how is the diameter, and thicknesses of the 4130 tubing determined. I'm actually learning TIG welding at the moment simply because I want to be able to weld 4130 tubing very well.

Sadly, I was hoping to go to Sonex today to pickup b/o parts ( AND get a sneak peak at the high wing).

[Skippydiesel]

Hi Bob,

Check back through this thread/Topic and you will see that some very talented builders have made their own Sonex/Rotax engine bed. The common theme is the Ring Mount. Some have made the whole system from scratch. Others have used the Rotax OM Ring Mount and adapted it to the Sonex airframe. In every case a better system that that offered by Sonex.

I admire your thinking - learn to weld properly before embarking on your own engine bed. As a retired agriculturalist , I can stick most metals together - to call this welding, would suggest a skill level well beyond anything that I would claim.

I doubt there is a Sonex/Rotax owner, using the Sonex/Rotax engine bed adapter, that would be happy with this barely adequate solution. The lack of interest/action, by Sonex, is possibly due to, what I suspect is, the low numbers of Legacy (A)/Rotax airframes using the adapter.

I wonder if there is a talented builder of a Sonex/Rotax Ring Mount, that would be intersted in building one for me????

[Skippydiesel]

Update:
Sent the offending exhaust header, in a good strong jig, to an expert in stainless steel welding.
His brief; pipe must end up in same places & angles in the jig but needs to introduce greater clearance (all specified from known point on jig).
Cut and tack welded part returned for trial fit engine/muffler - looks good.
Fully welded pipe will be back with me next weekend - fingers crossed there will be no more contact between it and engine frame.

[Skippydiesel]

Exhaust header has been modified & returned - looks good. Will install shortly. Test flight may take a little longer as cowl off for painting.

[Skippydiesel]

Follow up;

Remodeled left exhaust header has "done the trick" - no more marks on the witness material I put on engine frame.

Still not happy with the bed mount as a concept/solution but will persevere for now.

Note: Have learnt a lot more about bed mounts/Rotax - not a good combination, especially the 912ULS. Vibration could crack the Sonex engine frame.