Looking for MkIV 912 engine mount

[Jeromef 68]

Hello all

I have the project to switch my MkIV from 582 to 912 (as my current 582 is nearing the end of its potential)

However, Avid Kitplanes does not seem to sell engine mounts anymore. Has someone an idea where to get, either a complete engine mount, or at least the drawings to have one built from scratch by an aeronautical shop?

[1avidflyer 1944]

If one was to modify the firewall a little bit, a Kitfox mount could be made to work.  The Kitfox mount can be bought new from Kitfox for just under a thousand.  Every now and then a used one comes up for sale for a lot less.   I have several Kitfox mounts, and have put one up against my Avid MK IV project and it shouldn't be that big of a job.  

[Av8r3400 1172]

IMO, both the Kitfox and Mark 4 Avid mounts (which are basically the same) are terrible.  They are awkward to work on and expensive to acquire for what they are.  I would highly doubt that Kitfox Aircraft will sell you a mount without having a serial number for a Kitfox to put it on at least, even if then.  They are very backed up with building kits and LSAs.  Supporting the old (even the model 4) is not on their priority list any more.

The Rotax "ring" style mount is far superior in form and function.  Building the interface from the ring to your avid firewall will not be a major fabrication issue and in the end you will have a better system.

 

 

[1avidflyer 1944]

Hi Larry,  Do you have the ring mount on your kitfox?  I have  one but it moves the engine 5" further ahead than the standard Kitfox mount.  It was remodeled from a Kitfox 5 to fit the 4 firewall mounts.  Just the center two mounting points are different width I think.  But maybe it also projects further out than a Kitfox 4 ring mount would, I'm not sure.  The front face of the prop flange on the 912 is 29 1/2" from the firewall with this mount.  The standard mount measures 25 1/2" from firewall.  Maybe if you have the ring mount, could you measure the distance from firewall to prop flange face sometime??  JImChuk

[Jeromef 68]

If one was to modify the firewall a little bit, a Kitfox mount could be made to work. 

What is the extent of modification needed? Does it need to cut/weld airframe structural tubes?

Alternatively, would it be possible to modify the Kitfox mount to fit the Avid firewall fixation points?

[1avidflyer 1944]

The Kitfox mount uses 5 attach points.  2 at top and center, and one at the bottom.  The Avid uses 6 attachment points, 2 at top, and 4 points across the center of the firewall.  The center mount holes on the Kitfox mount is 11/16" narrower than the Avid.  If I did the modification, I would  weld another bushing to the outside of the existing center attachment points on the Kitfox mount, and then that area of the mount would fit the Avid mounting locations.  Would have to then add the two top mounting points  and the one low mounting point to the Avid fuselage firewall area to match the Kitfox mount.  I will have to look at it again today, to see how much difference in height there would be from the Kitfox to the Avid.  I have the Kitfox 4 unfinished fuselage, plus the Avid MK IV fuselage and a Kitfox motor mount as well, so maybe I'll get some pictures.  I looked at this last summer, but that was a while back and memories fade over time.  JImChuk

[Jeromef 68]

That would be very nice , thanks

[Av8r3400 1172]

Hi Larry,  Do you have the ring mount on your kitfox?  I have  one but it moves the engine 5" further ahead than the standard Kitfox mount.  It was remodeled from a Kitfox 5 to fit the 4 firewall mounts.  Just the center two mounting points are different width I think.  But maybe it also projects further out than a Kitfox 4 ring mount would, I'm not sure.  The front face of the prop flange on the 912 is 29 1/2" from the firewall with this mount.  The standard mount measures 25 1/2" from firewall.  Maybe if you have the ring mount, could you measure the distance from firewall to prop flange face sometime??  JImChuk

I do not have a ring mount.  When I was doing the rebuild, that was originally part of the plan to retrofit the ring to my plane.  With this in mind I build the plane with as much weight to the back as possible.  My CG is very aft compared to the Kitfox manual.  This was to offset the further forward position of the engine.

[1avidflyer 1944]

I got some pictures of the kitfox mount against the Avid fuselage.  I should have tied it in place and got a shot from further away, but I was up on a 8' ladder and was scared of dropping something onto my Avid parked down below me.  The first two pictures are the center mounts, you can see the mount is just a little narrower than the Avid mounting locations.  The next two pictures are of the top mount locations, and looking at it again, it may be easier to fit and weld new tubes from the mount to the current Avid top mounting locations.  The last picture is the bottom mount location, something would have to be added to the Avid there.  Interesting, if one put a Subaru engine on the Avid, you were supposed to put a mounting point down near the bottom.  I imagine there are some Avid drawings on how they recommended doing this.  Because the Avid tends to be nose heavy, anything that moves the engine forward would mean more weight in the tail to offset it.  I believe Joey Myers had to put 10 lbs of weight in the tail on his Avid MK IV after he installed a 912 using an Avid factory mount.  JImChuk

[wypaul 439]

I’m with Larry about the clunky nature of the Avid and Kitfox mounts.  If I needed a mount today I would have a bed mount built.

[1avidflyer 1944]

That mount looks nice Paul, but I think one would have to completely remodel the Avid or Kitfox firewall to use it.  Also, it looks like it puts the engine a good bit further ahead than the Kitfox mount.  On my Kitfox, I set the oil tank about 2 1/2" into the firewall, and it's very close to the engine on the front side.  The prop flange face is about 25 1/2" from the firewall with mine.  What plane is this mount used on?  Looks like if the oil tank was recessed into the firewall like I did, the mount could be shorter.  Here is my Kitfox firewall showing the box I made into the firewall for the oil tank to fit into.  Also, one showing the oil tank from the top and where the firewall is.   And the tank just barely does fit, height wise.  That space on the Avid it taller by 3/4" than the Kitfox so the tank would fit there for sure.  JImChuk

Edited 29 March by 1avidflyer

[nlappos 406]

Jeromif

Can I suggest that you consider swapping your 582 for a 670, at about 92 HP. I did this a few years ago, using a swap arrangement with Rotax Rick. The same 582 mount works well, and the fit is almost drop in, and you get over 90 HP. It is about half the cost of the 912 and very much less airframe mod. https://rotaxrick.wordpress.com/pricing/

[wypaul 439]

That mount looks nice Paul, but I think one would have to completely remodel the Avid or Kitfox firewall to use it.  Also, it looks like it puts the engine a good bit further ahead than the Kitfox mount.  On my Kitfox, I set the oil tank about 2 1/2" into the firewall, and it's very close to the engine on the front side.  The prop flange face is about 25 1/2" from the firewall with mine.  What plane is this mount used on?  Looks like if the oil tank was recessed into the firewall like I did, the mount could be shorter.  Here is my Kitfox firewall showing the box I made into the firewall for the oil tank to fit into.  Also, one showing the oil tank from the top and where the firewall is.   And the tank just barely does fit, height wise.  That space on the Avid it taller by 3/4" than the Kitfox so the tank would fit there for sure.  JImChuk

 

 

So this is a one off airplane known as the Outlaw.  A friend returned it to flight.  He built the mount which of course would not work on our planes and is only offered as an example.  One would need to build a mount to fit the Avid.  My oil tank is mounted beside the engine on the right side.  The original tank position was under the MK IV baggage area which worked fine.  No issues with weight/balance without adding any weight to the tail.

[Av8r3400 1172]

I’m with Larry about the clunky nature of the Avid and Kitfox mounts.  If I needed a mount today I would have a bed mount built.

That's a nice looking mount.  What airframe is this?  I have a friend building a Dakota Hawk (wood design) that is looking for engine mount ideas because the kit manufacturer is little to no help.

 

[1avidflyer 1944]

Hi Paul,  those don't look like Bing carbs...  And those gold extensions under the intake manifolds.  What is it?  JImChuk

Edited 30 March by 1avidflyer

[wypaul 439]

EFI FROM SDS no more Bings.

[Jeromef 68]

Many thanks JimChuk for putting your life at risk by taking pictures atop of a ladder!

The mods needed on the kitfox mount seem to be quite extensive and not easily doable by a basic shop!

That, and the need to demonstrate the flightworthiness of the extensively modified plane to the french aviation administration, make that I think I will stay with the 2 strokes for now!

[akflyer 1422]

I have built a few using the ring mount on the engine then my own design mount from the firewall to the ring mount.  Unfortunately, its time consuming even with the jigs I made to cut and cope the tubes then weld out the mount.  I get laughed at for the price even if I only paid myself 20 bucks an hour to build it.  No problem, go out and spend 3800 on a good tig machine, take the time to build jigs, buy the materials and teach yourself to weld.  I know its harsh, but there is a reason why people who have tried to build parts to support these planes have failed.  Everyone thinks that we should do it for the same price some dude in china is mass producing parts using shit materials and questionable welding practices can do it for.  Its not just a couple hour job to weld up a good motor mount.

[1avidflyer 1944]

Looked at this some more, and if I used a Kitfox mount, I'm thinking I would only modify the firewall at the bottom for the bottom Kitfox mount.  I would remodel the upper kitfox mount tubes to fit the Avid locations.  That will probably allow the carbs to stay in the original Rotax location, rather than switching them side to side like you have to do with the Kitfox mount.  Less work as well.  Still want to look long and hard at my Kitfox to make sure I'm not setting a trap for myself by not thinking of something that ends up being in the way.