Cutting off the motor mount

[japowell 4]

Does anyone have any pics of which tubes to cut off the front to remove the motor mount?

[sioux201 84]

 I have the original  instructions and construction drawings , and bolt on mount!

 It's not too much of a big deal to do, I did it 34 years ago on my a model #82

[japowell 4]

Sioux201, mine is welded on and I don't know which of these tubes stay and which needs to go.  I would love to have a full size set of drawings but all I have are the ones I copied from here.  Thanks for the help.

Jim

[Turbo 162]

The motor mount bolts on to the front of the firewall, at least that's how they came from the factory.

[1avidflyer 1983]

A model Avids did not have a removable motor mount.   B model and later did.  JImChuk

[smilemikey 3]

I'm too scared to cut mine off. Would love to be able to run a 4 stroke engine. 

[Allen Sutphin 705]

What engine are you thinking about for your A model?

[japowell 4]

I don't like the thought of mounting the engine upside down.  I am going to stretch and widen the mod a and hopefully add a soobie, at least that's what I am trying to do over the winter.

[1avidflyer 1983]

The Avid A model was designed for a 440 Cuyuna engine.  Maybe 80 lbs at the most.  With a 200 or so lb Subaru engine hanging off the nose, one will have a totally different machine.  And maybe not in a good way.  Avids have flown just fine and for a long time with inverted 2 stroke engines.  Nothing to be afraid of.  But it is experimental aviation...…  JImChuk

[Allen Sutphin 705]

I can pretty much promise you that hanging a 230 lb Subaru on the nose of an A model, you will not be happy. But who knows, you might work it out and it will be just fine. My model 2 came with a Subaru and was a single place with heavy ballast in the tail. Needless to say it went to trash can and will be replaced with a normal weight two stroke or comparable 4 stroke.

[FredStork 453]

I don't like the thought of mounting the engine upside down.  I am going to stretch and widen the mod a and hopefully add a soobie, at least that's what I am trying to do over the winter.

Hi! What is your concern with the engine upside down? The only real issue I see (and have experienced now on my second upside down 2 stroke) is the tendency to to get oil in the spark plugs when not flying for a longer time (but we have the solution to this, just use "P" model spark plugs).

The lighter the Avid is the better it behave and the more fun it is to fly. I know everyone want 4 strokes today but personally I think even the 912 is too heavy. 

[japowell 4]

Don't know guys.  Still kicking it around.  If I don't go with a soob the I wouldn't need to stretch the fuselage, just widen it.  I know challengers run the engine inverted with no problems.  How does the 582 perform on the A?

 

[1avidflyer 1983]

With a 582 on a light weight Avid, you would have a little rocket ship.  (Not that it's influencing my posts here, but did I mention I have a couple of 582s that are for sale?  Have a Subaru with a gearbox on it also for that matter that I would let go cheap.  )  Seriously though, the 582 would be a great performer in a 400-450 lb Avid.  JImChuk

Edited 19 Nov 2018 by 1avidflyer

[efil 01 74]

you can go with hks700E , it can be good 4T for light avid

[japowell 4]

Okay fellows, I cut the motor mount off and bought the one on Barnstormers.  The plans I have were down loaded from this site and do not show how the correct way to install the bolt on mount.  When I look at several pics on here of the mounts and try to copy the location on mine, it seems too high.  What is to proper location on the motor?  I can always move the mount to fit that dimension,  Thanks Jim

 

[Allen Sutphin 705]

I flew a challenger for 6 years with an inverted 503 and never had a issue. The plugs did collect some oil after a week of sitting but still started just fine, and I was using BR8ES plugs. My model 2 will have an upright engine just because its easier to work on and no other reason.  I just wish I could find a reverse flow fan for my Hirth, it would cool 100% better but evidently one does not exist. Anybody have a 3D printer?

[TJay 1041]

I flew a challenger for 6 years with an inverted 503 and never had a issue. The plugs did collect some oil after a week of sitting but still started just fine, and I was using BR8ES plugs. My model 2 will have an upright engine just because its easier to work on and no other reason.  I just wish I could find a reverse flow fan for my Hirth, it would cool 100% better but evidently one does not exist. Anybody have a 3D printer?

Could you just cowl it different and run it Free Air?

[1avidflyer 1983]

Okay fellows, I cut the motor mount off and bought the one on Barnstormers.  The plans I have were down loaded from this site and do not show how the correct way to install the bolt on mount.  When I look at several pics on here of the mounts and try to copy the location on mine, it seems too high.  What is to proper location on the motor?  I can always move the mount to fit that dimension,  Thanks Jim

 

Here are a few pictures of my MK IV.  Maybe there is enough there to give you an idea of how high things should be.   If this doesn't take care of it, can you post a picture of you firewall area?  JImChuk

[japowell 4]

Thanks Jim.  I guess what I am really asking is with the plane level, what is the dimension for the center line of the prop?  Jim

[Allen Sutphin 705]

I flew a challenger for 6 years with an inverted 503 and never had a issue. The plugs did collect some oil after a week of sitting but still started just fine, and I was using BR8ES plugs. My model 2 will have an upright engine just because its easier to work on and no other reason.  I just wish I could find a reverse flow fan for my Hirth, it would cool 100% better but evidently one does not exist. Anybody have a 3D printer?

Could you just cowl it different and run it Free Air?

I don't know how well it would cool with free air. I know that the fan does an incredible job of keeping temps in check. Even in the challenger with forced air feeding the fan, if the belt breaks, you've got about 1 minute till things get quiet. I've seen several aircraft w/2 strokes that are always running on the ragged edge of overheating free air style or original fan configuration. The style of flying I do, overheating cannot be an issue. A reverse flow fan is the logical answer even if I have to have it made special. It might be possible to mount an electric fan in front and remove the rear one but the rear style fan is very efficient. Picking up hot air from the rear and sending it forward and out to be picked up again isn't good form. If I can't design a fan, I probably shouldn't be fooling with airplanes.  Some homebuilder (Dean Wilson) built a homebuilt to fly to the pole!

[1avidflyer 1983]

That would depend on what engine you are going to mount I believe.  I will try to measure from the floor boards up to the lower holes on my Avid tomorrow.  That will give you something to work with I think.  Post up the picture of your firewall if you can.  That should help.  JImChuk

[1avidflyer 1983]

Allen,  a friend of mine flew his Avid A model with the 55 HP Hirth for quite a few hours, with the fan set up like yours, and he didn't have issues with CHTs that I remember.  He flew it close to 200 hrs with that engine.   Maybe you really don't have a problem that needs fixing.   I had a 447 free air in my Himax, and never had issues with overheating on it either.  Course we do live in northern Mn.   JImChuk

[japowell 4]

Jim I will be using the 582 w/c box.  I have my firewall kinda set but not really.  I was waiting to get my engine set before I installed it. I will attach a pic of what I have now.  All of this is preliminary.  Still trying to figure it out.

[1avidflyer 1983]

Looks like you have that same long cross bar where the 4 lower mount holes go that is on later Avids.  I'll measure tomorrow on mine, if they are the same height, that should determine your height of the mount.  JImChuk

[1avidflyer 1983]

I was able to measure some things on the MK IV today.  My long cross tube is about 11" to the center off the floorboards just behind the rudder pedal cross tube.  The very front bottom cross tube is about 18 3/4" to center of joystick cross tube.  Also, I'll include a picture of how the extra side tubes are built.   The plates the rudder tubes bolt to should extend to the front cross tube.  It will be stiffer then having them just supported on one end.   JImChuk