SonexBuilders.net

Hi,

I have just received my Sonex supplied ACV-P54-Kit Rotax Engine Mount Attach Kit - no installation instructions.

Have done a search of the Sonex web site - so far no instructions. Will keep looking.

The kit looks fairly self explanatory, however I would like to know;

[list=]Is there a proffered mounting orientation for the mounting rubbers?
Where do the 4 big washers fit?
Is there a torque setting on any of the nuts/bolts?
Any other instructions?[/list]

Does anyone know where I can find/get installation instructions for this kit?

More problems!

Sonex have very quickly & efficiently sent me additional information (annotated drawing) & photos - very helpful - thanks Kerry.

Unfortunately the adapter kit does not fit my Legacy (A) model Sonex engine frame. The problem would seem to be the adapter kit comes supplied with AN 5 bolts (& holes) to attache from the lower adapter plate to the Sonex engine frame - my aircraft has the smaller AN 4 bolts (I hope I have the AN's correct, as all new to me).

When I ordered the parts, the form asked for my Plans Number - I gave it, so Sonex should have had all the information necessary to supply the correct parts - basically a lower plate with AN 4 hole size, rather than AN 5, would have been sufficient. New AN 4 bolts/nuts/washers would have been a bonus but not absolutely necessary.

I have just found out that this problem was raised, by another builder, with Sonex in May last year, so ample time has passed to get this right.

Update;

Sonex has speedily responded to my concerns.

They have alluded to changes that are already underway (not before time) but seem to be rather stuck on a particular business model (part of which relies on the customer, figuring things out for themselves) which I believe does not serve them or their customers as well as a more professional holistic approach might.

They are under new management - lets hope the management gets up to speed ASAP.

Fitting of the Sonex/Rotax engine frame adapter is not going well.

It seems that the bottom brackets, the ones that mate up with the Sonex frame, are too short by about 1.5 mm.

Have asked Sonex for help - will get back to you when they reply.

Not getting much (any) help here!

Should not have to do this (factory problem) but I have a potential solution for your comment;

It would seem that I need to end up with a 1/4 hole off centre to existing hole. I feel that this will necessitate enlarging existing 5/16" hole and then filling it, to allow for enough "meat" to drill a completely new mounting hole.

Drill out one of the 5/16 exiting mounting holes to 3/8" (or there about)
Mill an, interference fit, plug, from 6061T6 alloy, to suit above.
Fit plug.
Mount bracket using MN 4 bolt in non plugged hole.
Using a 1/4" drill bit, hand run through Sonex mount, mark plug
Drill plug to 1/4"
Use extra wide washer (wider than plug) for security.

Why not replace the parts with existing holes?

Skippydiesel wrote:It would seem that I need to end up with a 1/4 hole off centre to existing hole. I feel that this will necessitate enlarging existing 5/16" hole and then filling it, to allow for enough "meat" to drill a completely new mounting hole.

I "botched" the 1/4in holes in my Tracy O'brien gear legs. I had a machinist "move" the center of the hole with a resulting 5/16 hole. Picture a small circle inside a larger circle with their edges touching.
It was then a simple matter of using a piece of 5/16 tubing with a 1/4 ID (bushing stock) to fill the hole.

Bryan Cotton wrote:Why not replace the parts with existing holes?

? Not sure what you mean (could even be tongue in cheek) but if its exchange the Rotax engine bed adapter for another, in the hope the second set will match the Sonex frame - might be something to consider if I lived in the USA.

Just received the Sonex response to my enquiry;

"That mismatch between a precision machined parts and weldment is not unusual. The correction is to ream the tubes the on the engine mount that the bolts pass through. That will give you play for the alignment".

This will certainly allow the 1/4 in bolts to "line up" with the hole in the lower Rotax bracket.

BUT

The 1/4" (AN4) bolt is marginal - Sonex now supply a 5/16 " (AN5) bolt to do this job.
Introducing the potential for unnecessary movement, in this critical part of the engine mounting system, can not be a good thing for ongoing structural integrity.
I will go with my proposal (unless someone comes up with a better idea) as it preserves the integrity of the bolt attachments.

On the comment "That mismatch between a precision machined parts and weldment is not unusual" may be reasonable/acceptable when I, an amateur welder/machinist without the aid of jigs, etc, make something but is quite alarming for a supplier of aircraft kits/parts to state.

Many of your concerns have been addressed before: viewtopic.php?f=60&t=6451

Sonex reports that the AN4 bolts are sufficient. NAS shear bolts are available in .250" if you want extra margin.

Expecting a "tight fit" between a machined part and a weldment is unrealistic for the price. My reamers got a lot of use during my build, I consider it part of the process. I would follow the Sonex directions but I would clean up all four bolt holes on the engine mount with your reamer. 1.5mm / 0.060" is not much, I think it would clean up fine.