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Post by renard80 on Mar 12, 2012 1:36:00 GMT 1
Tip-overs on landing and hard crashes can damage the fragile plastic firewall. This damage typically occurs where the motor mount screws enter the firewall. With my rebuild, I have put a rubber pad between the motor mount and the firewall. I hope this will cushion and spread any impact while also damping motor vibration while flying. If it doesn't work, I will post again . . . I made the rubber pad by cutting up the inner tube of an old tyre (US = tire  ). I used a double thickness for extra cushioning. (In case you are wondering, the yellow spots in the pictures are the ends of cocktail sticks, inserted to strengthen the fuselage - I hope . . . )   |
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Post by larkshead on Mar 16, 2012 18:31:19 GMT 1
Renard,
Just brainstorming here: What if you removed a "bread slice" from right in front of the windshield and replaced it with a slice of a softer foam? Not too soft or the engine's torque and prop pull might distort it. Maybe something like a gardener's kneepad, a mechanic's floor mat or a boating lifesaver. Weight could be an issue, too.
regards,
-Peter
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Post by renard80 on Mar 18, 2012 0:14:16 GMT 1
Hi Peter I'm not very practical so can't comment too much on your idea. It could work! However, my immediate thoughts are: (1) besides the torque issue you mention, the material of any replacement "firewall" would have to be strong enough to accept the screws bearing the weight of motor, mount and prop; (2) it would be necessary to mod something to secure the cowl, which normally screws into the plastic firewall. The more practical members may wish to comment further. (I flew her yesterday and for some reason a brick building suddenly jumped out into her path while I was landing  . Fortunately I had throttled right back but still it was a head-on impact. A good test of my rubber cushion! I haven't had the time - or the nerve - to remove the cowl for inspection, so fingers crossed . . . ) |
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Post by larkshead on Mar 18, 2012 1:56:21 GMT 1
I'll keep my fingers crossed, too. Good luck with that.
I wasn't suggesting that the "bread slice" extend all the way to the firewall. I had in mind that it would extend from just in front of the windshield to about 3/8 to 1/2 inch behind the firewall. The firewall would still attach to a slice of the normal foam. You would end up with the slice of new foam sandwiched between fore and aft sections of the existing fuselage.
Of course I haven't actually tried this. It's just in my head...
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Post by john66 on Mar 19, 2012 20:44:45 GMT 1
Fingers crossed for ya too Ian! Very interested to know/see how your dodgem mount worked out?
John
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Post by toff on Mar 19, 2012 21:59:23 GMT 1
As a thought, how about cutting some thin ply to shape, glueing the foam to the ply. Hot glue/ silicone the ply to the firewall, then drill the mount into the ply? Can't see why that wouldn't work.
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Post by john66 on Mar 19, 2012 23:06:43 GMT 1
Hmmmm, fingers crossed for a good result...."The Renard Dodgem Mount....RDM" Now Im sure we could market this! ;D
John
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Post by renard80 on Mar 20, 2012 1:20:16 GMT 1
Right, you lot!
Having finally found a tiny window of opportunity in my extremely busy schedule, I removed the cowl today - to discover that the firewall is completely undamaged. ;D
So I am off to the Patent Office first thing tomorrow to take out a patent on my rubber mount before John craftily markets it.
I understand that John usually dislikes using a rubber. But probably he would still market my rubber device, perhaps calling it the "Rubber Johnny".
On a more serious note, Toff's plywood add-on suggestion is something I, too, thought of many moons ago. Difficult to know what glue would stick it to the firewall plastic but perhaps just screwing through the ply would be enough to spread the load and avoid damaging that fragile firewall.
Has anyone tried affixing a plywood firewall?
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Post by john66 on Mar 20, 2012 9:04:03 GMT 1
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Post by geoff2474 on Mar 20, 2012 21:17:03 GMT 1
Hi Renard
My other hobby is my motorhome, great to get away when and where we please.
The caravan motorhome industry use some very effective adhesive-sealers for fixing and/or sealing just about anything.
One that I have used many times is Sikaflex 512, there are other equivalents available (try Google) It will stick to almost anything and has a 300% elasticity before the bond will break. It can however be separated with a sharp knife or similar. The remainder can be removed reasonably easily. I have used it many times on my planes with excellent results. I have yet to find something it will not bond to.
One thing which may appeal to you, in your particular application, is that you must ensure an adhesive bed of at least 2mm, this will have the added benefit of allowing a degree of flexibility.
One point to remember if you go to purchase some is that it has a shelf life, this is quite generous but I have come across tubes with expired dates for sale, just walk away from these.
If you just want to try some, visit your local caravan/motorhome repairer and ask for a squirt, you will not be disappointed.
Geoff
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Post by ginginho on Mar 21, 2012 9:46:54 GMT 1
....ask for a squirt, you will not be disappointed. Geoff This could be taken in totally the wrong way.  |
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Post by geoff2474 on Mar 21, 2012 10:50:51 GMT 1
....ask for a squirt, you will not be disappointed. Geoff This could be taken in totally the wrong way. Could make an old man very happy!!!!!!!!!! |
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Post by renard80 on Mar 21, 2012 11:55:20 GMT 1
This could be taken in totally the wrong way. Could make an old man very happy!!!!!!!!!! Seems I started something with my mention of Rubber Johnnies . . Thanks for the adhesive tip, Geoff. My brother-in-law is well into caravanning, so he may have some in his workshop for me to try. |
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Post by john66 on Mar 21, 2012 12:27:48 GMT 1
Could make an old man very happy!!!!!!!!!! Seems I started something with my mention of Rubber Johnnies . . Thanks for the adhesive tip, Geoff. My brother-in-law is well into caravanning, so he may have some in his workshop for me to try. Hmm, if asking for a squirt is likely to be taken the wrong way...man in shop or bruv in law? I just cant make my mind up! ;D John |
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Post by larkshead on Mar 22, 2012 12:04:18 GMT 1
I used this 2.25 inch rubber washer from the local big-box home improvement store. I found it in the specialty hardware bins for just over a buck. It makes a very clean installation.  regards, -Peter |
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). I used a double thickness for extra cushioning.
. Fortunately I had throttled right back but still it was a head-on impact. A good test of my rubber cushion! I haven't had the time - or the nerve - to remove the cowl for inspection, so fingers crossed . . . )
