GA piston engines - Cylinder Girdles

[nomorecatering]

Recently i was watching a slow motion video that was showing a 6 cylinder GA engineat full power and was quite amazed to see the cylinders waving around like leaves in a wind. The amount of movement was quite stagering.

There is a company that claims to have a fix for this. Where they have the rocker covers for all cylinders on each each side as one very solid unit and then have a number of cross brace bolts tying the oposite sides together, much like a strut brace a car.

They claim its very effective in making the engine much more rigid in very high power aerobatic operations, but would it pay any dividends on normal stock engines, especialy in terms of reliability.

The premier manufacturer of performance aircraft exhaust systems and engine components. (http://www.skydynamics.com/frame.htm)

[Tu.114]

Sounds interesting - but actually, what is the necessity behind such an addition? The engine should be designed to withstand those vibrations also without those additional struts and braces; tying parts together that are not meant to would change the vibration patterns and possibly induce loads on parts that were not meant to bear them. Compare an unbraced cylinder moving like a reed (hinged on one side) vs. a braced one vibrating like a string (hinged on both sides) - the bending moments seem rather different.

[717tech]

Wouldn't have a link to the video? Would be interesting to see.. I couldn't find it through google or YouTube.

[A Squared]

Sounds interesting - but actually, what is the necessity behind such an addition? The engine should be designed to withstand those vibrations also without those additional struts and braces; tying parts together that are not meant to would change the vibration patterns and possibly induce loads on parts that were not meant to bear them. Compare an unbraced cylinder moving like a reed (hinged on one side) vs. a braced one vibrating like a string (hinged on both sides) - the bending moments seem rather different.

Thast's what I was thinking. Additionally, if you have two adjacent cylinders vibrating up and down, 180 degrees out of phase with each other, he you tie the heads together that would introduce a moment around each cylinder's axis which didn't exist before.

It's worth noting that nowhere on that site could I find any reference to an STC for the modification. That would lead me to believe that there isn't one, which means it's for experimental aircraft only.

[Yeelep]

The aircooled Porsche 911's have no issues with the cylinder heads on each bank tied together by the cam carrier.

Pretty obvious from the link that they are primarily for use on highly modified non certified engines.

[A A Gruntpuddock]

I would have thought that significant movement of the cylinders on a non-ohc engine must have significant effect on the valve clearances.

[bcgallacher]

Lycoming and Continental engines have hydraulic tappets in the valve train which keep the valve clearances at zero - they are self adjusting during every opening/closing cycle.

[A Squared]

Lycoming and Continental engines have hydraulic tappets in the valve train which keep the valve clearances at zero - they are self adjusting during every opening/closing cycle.

Not all of them. The Lyc O-235/O-290 series has solid lifters.