Engine Mount Rubbers

[Murray Parr]

Hopefully you haven't put your order in yet. I would like to get a set of the -14's as well if you would like to go halves in the shipping.

[Skippydiesel]

Phone you tomorrow Murray.

Have local supplier, going to give me a quote on the 14's, when he gets back from annual holiday.

[Skippydiesel]

1. "To try & preserve as much of the Sonex recommended system (22001-13) I will start by replacing the lower donuts with the 14 donuts and see if that has the desired effect."

As a first step, I think the above is small, therefor may not result in sufficient movement reduction, so planning for the future (if needed);

2. The lateral movement, viewed from the cockpit, is to the left. With this in mind, could step two be replacing the two - 13 mounts, on the left side only, with the stiffer -14's. What might be the negative effect of mixing two diffrent mount stiffness (Note: All 22001 mounts have the same dimensions)???

3. It seems that the rear/aft mounts are being subjected to more movement that the front two - Should I consider replacing the aft mounts with -14's leaving the front two -13's? As in 2, what might be the negative effects??

4. I will be purchasing 4 X - 14 mounts, so if step two/three don't have the desired effect OR are skipped (due to advice/reflection) I will just replace all -13's with -14'. Aside from checking for desired movement reduction, I would appreciate any advice on what I should monitor ??

[Skippydiesel]

So I now have the Hutchinson/Barry Controls 22001-14's fitted.

In my last post I had planned to substitute bits & pieces of - 14' s only going to fully replace the -13"s as required, however the suppliers of the mounts advised that I just replace the -13's completely. They seemed to know what they are talking about (30 years in the vibration control business) so went with their advice.

My Sonex is based on a grass strip, very wet at the moment, so no flying but hoping for hot dry weather over the next few days, to dry it out and then I will test/report back on the -14 mounts.

[Skippydiesel]

I have just done 1.4 hrs (2 engine starts) with the new Barry 22001-14 mounts (with my Cupped Snub Washers) in place .

Did not notice any major change in vibration/noise - possible very small increase in HF vibration through control stick.

Significant improvement (reduction) in lateral movement but still just marking witness tabs.

Next step - add the Sonex supplied spacer washers ACV-P54 -06 & -07 .

[Skippydiesel]

Have done 2.4 hrs with the new Sonex spacing washers (FYI: - they have a larger OD & are better machined, than the original supplied - they actually fit without further adjustment).

Again some improvement BUT still getting a touch, between rear right exhaust header and engine frame.

Options;

Go another step stiffer with the Barry Controls engine mounts to part number 22001-15

OR

Have the offending exhaust header reworked/new build, with slightly wider clearing curve - this last is possibly the best solution, as preserves the engine mount(s) vibration control while allowing damping movement BUT as is often the case, the most costly and time consuming

[Skippydiesel]

It has been suggested, on another Forum, that making a strategic dent/depression, in the existing & offending exhaust pipe, to enhance the clearance between it & the frame, would have little impact on the cross sectional area of the pipe and therefore be unlikly to result in any engine performance loss - what thinks the Brains Trust??

If you agree with this proposal - how would you go about it? eg would you heat the pipe to plastic stage & then press/hammer in the depression, fill the pipe with sand to reduce unwanted distortion, do the aforementioned cold, etc

[Skippydiesel]

It has been suggested, on another Forum, that making a strategic dent/depression, in the existing & offending exhaust pipe, to enhance the clearance between it & the frame, would have little impact on the cross sectional area of the pipe and therefore be unlikly to result in any engine performance loss - what thinks the Brains Trust??

If you agree with this proposal - how would you go about it? eg would you heat the pipe to plastic stage & then press/hammer in the depression, fill the pipe with sand to reduce unwanted distortion, do the aforementioned cold, etc

I will need a dent of about 10 mm in depth (in a 25 mm pipe) to be assured of not contacting the frame, in a poorly executed engine stop.

Have a look at this automotive experiment, to assess the effects of denting the exhaust system:

https://www.facebook.com/watch/?v=152724102049876

[Skippydiesel]

Update!

Finally bit the bullet and had my right rear exhaust header remade/adjusted, to give about 12mm extra clearance to the engine frame - seems to have done the trick. No evidence of brushing/touching in about 3 hrs of flying.

I have added one additional washer to the front two rubbers. This is to slightly change the prop thrust line, to reduce the amount of up elevator in cruise - seems to have worked. Carrying weight (max 18KG) in the luggage compartment behind the seat, has a similar effect.

[Skippydiesel]

Follow Up!

So far so good - now at 108 hrs. No more contact between engine & frame/cowling.

Bit concerned about a carburettor float chamber fuel overflow, out of breather pipe - may be due to high frequency vibration "foaming" fuel. Exploring options/fixes.