Engine Mount Rubbers

[Skippydiesel]

FYI -

Email from Hutchinson (Barry);

"Thank you for your interest in Hutchinson product.
Our recommendation regarding the isolation system would be to adhere to the engine manufacturer guidelines, however if you are looking for a stiffer isolator that has the same geometry it would be 22001-14 or 22001-15
The -14 is one step stiffer and the -15 is two steps stiffer.
Installing a stiffer mount will mean that you will control motion a little better, but will sacrifice some of the isolation efficiency.

Should you require a quotation for any of these parts for pricing and lead time please contact any of our value added distributors listed in the link below:"
https://hutchinsonai.com/distributors/

[Skippydiesel]

I have installed the Sonex stiffening washers and find that:

They have made little if any difference to my engine movement, which is still around 15-20mm at the top of the gearbox.
The rear, bottom, rubbers have moved/displaced, in particular the right-hand side.

I am now thinking that the next step, is to try the Barry Control Mounts 22001-14 being the next level of stiffness above the Sonex supplied 22001 - 13 mounts.

How are all the other users of the Sonex/Rotax adapter rails doing?

[Kai]

An interesting question!

I am sure there are more than me and Skippy who would like to learn more about this.

[Murray Parr]

I was experiencing very heavy right yaw and also the same engine movement to the left and down (rub marks at the 4 o'clock position when looking at the cowl from the front). I was needing 3/4 to the floor right rudder input with any amount of power above 3000 rpm and slight left rudder without added power (I even ran out of rudder with a 5-knot x wind). After installing the upgraded washer kit, this improved somewhat, needing 1/2 to 2/3 rudder input under full power.

I now have 10 hours with this modification and the right yaw problem is worsening again, needing close to the original 3/4 right rudder input under full power. I can't see any deformation of the rubbers but suspect they might be squashing a bit. I have the earlier B model Rotax tail dragger mount that only has the 1/4" bolts holding the MK2 bed mounts to it instead of the 5/16" the later ones have. I would like to add a couple of degrees right thrust to this setup and either go up one Durometer in stiffness or add a 3rd set in between the other 2 like the original design concept had. I really think Sonex should consider adding right thrust into this system as standard as it definitely needs it.

I tried to add a washer behind the left engine mount attach points at the firewall, however I couldn't seem to be able to relieve the pressure on the bolts so I will most likely have to remove the engine to achieve this. Might be easier to re make the bed mounts with 2 degrees of right thrust.

[Skippydiesel]

Hi Murray.
All the best to you & yours for the coming year.
In comparison - my Sonex requires corrective right boot only during TO/CO.
I am still fiddling with small incremental changes to the trim (recently went backwards ) but very close to what I hope will be the final setting.
I have a small rudder trailing edge fixed trim, to correct a slight wings level yaw (bubble not quite centred) and my flaps are at slightly diffrent angles, to level the wings (hands off).
My aircraft has always required some up trim of the elevator (neutral when baggage compartment filled to 18Kg) To try & counter this, I have raised the front of the engine slightly, (before/after change aproximately 6mm tilt at prop tip) by adding 1 X 1mm flat washer to each front engine rubber stack . I think it has had a posative result, elevator up trim reduced.
I am hoping that the latest adjustments will in fact be my last & I can install the flap/fuselage gap seals (waiting for runway to dry out, so I can fly).
Does not apply to your aircraft but just letting any reader with/contemplating wing tanks - the quantity of fuel has a significant effect on lateral trim (as you may expect) so care must be taken, when transfering in flight, to try & keep fuel levels similar.

[Murray Parr]

Hi Murray.
In comparison - my Sonex requires corrective right boot only during TO/CO.

How much rudder do you need, anything like the 3/4 of the way to the floor like mine needs?

[Skippydiesel]

Hi Murray.
In comparison - my Sonex requires corrective right boot only during TO/CO.

How much rudder do you need, anything like the 3/4 of the way to the floor like mine needs?

To be honest I don't really take much notice of the amount of corrective rudder. Seems to be much the same as my Zephyr. I expect to counter the turning effect of the prop/accelerating aircraft, so just roll with it.

Once I level out and she accelerates, resting (no force) my foot on the right rudder pedal, centres the ball - hopefully the small trim on the rudder will allow both my feet to be flat on the floor during nice level cruise.

Next flight, I will try and take notice of just how much right rudder I use in TO/CO.

[DCASonex]

What is the direction of rotation of the Rotax prop? I need a lot of right rudder in my A series tail dragger Sonex with its CAMit engine. Have to hold some right rudder in climb, but none in cruise. You might just be seeing the effect of the prop. The more HP the greater the effect.

David A.

[13brv3]

Rotax prop turns clockwise viewed from the rear.

[DCASonex]

Clockwise viewed from the rear is same as CAMit and Jabiru engines but I think is opposite that of AeroVee engines.

David A.