I have been messing around with a somewhat different motor mounting scheme that has helped me out of a couple of binds - thought I'd show it off here to see what the gang thinks.

When doing a rear mount on the firewall it is sometimes a pain in the patootie to slip the motor down through the nose ring and in front of the firewall.  Getting to the upper two mounting bolts is also a bit of a challenge.  On the original Strega testbed build I resorted to poking two holes that sorta look like gun ports in the forward top block so I could get a ball wrench onto the top bolts.  I remove the fiberglass cowl to get to the bottom bolts, and I cut a slot in the nosering to let the motor shaft slide past.

Recently tried mounting a motor in a fiberglass fuselage & discovered that the X mount would not fit through the opening at the front of the fuselage without major rework.  I had a lot of room from behind through the battery compartment - I figured out that I could make the firewall with a motor sized hole in it and install the rear mounted motor THROUGH the firewall and run the mounting bolts FORWARD.  This results in a super clean & easy installation with good control of the airflow out of the motor compartment.

Later I did another Strega conversion, this one for a fuselage that Brodak could use at trade shows & such.  Mindful of the issues with the first Strega, and with a huge battery compartment to work with, I located the firewall a wee bit forward (about 3/8") and installed the motor on the X-mount from behind and through the firewall.  Again, it was very easy to do and results in a very easy installation of the motor through the battery hatch without removing the cowl.

This probably will not work everywhere because you need to have a pretty good alignment of the battery box and the firewall.  Obviously it would not work well on a profile either.  However, on the two installations described it was the best way out of the problems I faced.

Note also that doing it this way, you can pretty easily incorporate an extra external support bearing.  Put a flanged front bearing into the nose ring structure and simply slide the motor in from behind, passing the motor shaft through the bearing with the prop adapter sliding on after...

Whatcha think?

Dennis,
Thank you for the pictures.  I might try something like this on the E-vector.  My current one has the gun ports that you described.
John

With this setup looks like you could shim the mount for motor centerline aligment and spinner gap by placing spacers between motor mount and firewall.

Bob: you nailed it - on the installation shown the top of the firewall is captured but the top block, it would take no stretch of the imagination to see how the same thing can happen on the bottom.  The motor compartment can be sealed to force the airflow path, and/or a separate patch can be provided via the bottom half of the chin scoop to chill the ESC & battery.


John P: as you know the Vector is quite small & snug up front, but the battery (tank) compartment is quite large providing easy access for a through-the-firewall mount.  You can hollow out the forward parts to almost nothing, maybe cover with a layer of glass cloth to improve the continuity of the front end structure.


Lineheart: I agree that front ended mounts and especially double ended mounts (external bearing) will soon be the norm when using 12" & greater props.  For 11" or less I think the simple rear mounts are viable, though front mounting will STILL be a good idea especially with smaller motors & motor shafts.  I even built (almost finished) my Wee Duper Zilch with a 2210 motor that is front mounted.

As far as "copying" goes, your Bearcat was one of the first 3 electrics I ever saw and one of the birds that compelled me to "jump in" - loved it then and now, looking forward to seeing you and the Bearcat again.


John R: the shimming possibilities you mentioned are all the same as with a "normal" front side firewall mounting - just be mindful about messing up the thrust alignment.  PLUS with the scheme shown you can if needed) also use a longer motor by adding shims to push the X-plate BACK.

Crist: Can't claim its earthshaking but it did help me out of a couple jams...

Dennis
Are you concerned at all with flex of the mount? There is not a lot of structural integrity there for the power it seems. Remembering the flex issues I ran into with the strega with the motor on the paired up aluminum angles and that we had to double them to get rigidity it seems like it could be an issue, particularly on a larger plane. With the Strega, why not just move the firewall back the 3/16 or so and have the rigidity of a more solid firewall. Air can still be guided around as needed as we know. Not ment as a criticism, just a question. Have you run the strega with this mount yet?

bob branch

Go to 1/4" ply and the flex becomes moot.