Just wondering how any of you DA 85 owners have mounted the new DA 85 to your firewall ??

DA says must be solid mounted (custom mount required, right ?? ) per manual.

NO STAND-OFFS !! I am building a AW 75cc QB and have the DA 85 coming and just
need a little help in this area. I really can't understand why 1" standoffs won't work with large washers on each side of firewall to spread the thrust.

What if small thrust changes are required by an additional degree or two when trimming the plane out with a Solid Mount (No washers can be used like with stand-offs) ???

Stand-offs are used on alot of big gas engines I thought.

PICTURES are greatly appreciated.

Thanks for any help !!!!

niteman

Just a guess on my part, but I think they may be refering to not using flexable or Isolation mounts, rather than not using standoffs.

Mike

Actually 3W engines have the same requirement and what I've done with them is to make a lite plywood mount that is a bit too large in certain areas and cut it out in the middle for the carb. Then in the "too large" area drill for 1/4 bolts and use standoffs between the mount and the firewall.

I'd post a pic of mine but that cannot happen until tomorrow. I've seen tons of pics all over the place on doing this type of system

I did find this on AI's web site to give you an idea

http://www.aircraftinternational.com...ting/index.htm

Also, look at the assembly manual for the 75cc or the 100cc Aero-Works Yak. One of them (sorry I forget which one) shows a mounting plate they designed for the DA85

I did a similar thing on my QQ Yak the engine is solid mounted to the ali units and then flexably mounted to the firewall, it also gets over the horrible feeling that the bolt hole is too close to the clearance hole for the carb.

Mike

Hi bubbagates,

Had thought about the same idea. A 1/4" mount oversized, then use standoffs to the firewall so you can still adjust the thrust if needed.

Did you glue or laminate the plywood with a carbon sheeting ?? kinda looks like that ??

If you can at your convenience, like to see any other pic's you have. I'm abit challenged in this area of custom mounting.

Thanks alot. Dan

Dan,

I actually added a layer of fiberglass to mine to help keep it lite. I also have used a flat aluminum plate and on one 3W used their mount. The idea is to take the twisting load off the crankcase.

If you are building the AW 75cc Extra it comes with the DA85 mount in the kit. Its a solid ply spacer, no need to use standoffs.

Thanks bubbagates and everyone for all of the advice. Please any pic's really help.

The plane is the Yak 54. I have the 50 cc and love it !!

Gotta have the 75cc red leading edger !! Can't wait to try it out !!

Dan

Dan,

As jbarnes and I said, the aero-works Yak comes with the mount you'll need. Just follow the instructions in their manual and you'll be fine

Hi bubbagates

The AW 75 QB does not cover the new DA 85 at all (no template, mount, etc...). I asked the guys at AW if they had any spare templates or the custom mounts they are using for the new extra and they do not have any extra sets, just whats in the Extra's kits at this time.

Would have been nice and easy though.

AW 75cc Extra 260 with DA 85. Shows the .970 ply spacer that comes with the plane. I shimmed mine an extra 1/8 inch.
I have not flown yet and can’t comment if any change of thrust is needed.
I can say this is a very impressive ARF construction wise.

Jaketab

This is how I did it on a H-9 Cap i think i cut this week from scraps lying around the house to make this box, as I to saw were they Da did not seem to be pushing stand offs....

It's supposedly in the 75cc Extra 260 and not the Yak, my bad

There's a pic of the mount on their website and in the manual starting on page 43

bubbagates your bad !!

Seriously, really appreciate everyones reply. I'll get the chain saw out and fabricate a mount from one of my old Beech trees as needed !!

I really can only see that the advantage to mounting the engine solidly so that the entire engine is snugged to a solid (flat surface)firewall or mount is purely to control "excess" vibration and not as a matter of controlling backlash and torque in lieu of a good quality standoff like the SWB stuff, especially when the standoffs are used with solid spread washers on both sides of the firewall. Thats pretty solid as well.

Even on a solid firewall mounting you are still fastening the engine with 4 - 1/4" bolts, same as the SWB stand-offs, right ??

Am I missing something here ?? I know the DA guys obviously had to do the homework, just trying to figure it out.

Dan

Here's a picture of the mount I made for my 85. The mounting plates are made from 3/4" maple cut on my scroll saw. The shape of the mount matches the plan view of the rear engine mount so it's light. I applied fiberglass resin on the inside and outside of the mount. The other side of the mount has a hole to get at the carb needles for adjustments.
Regards,
Steve

Hi Steve,

Great Job on the mount. Clean professional-sturdy. Only concern would be if you have to shim with a washer or two for thrust adjustments for fine tuning the plane.

The minute you pull the engine away from the hard mount with a washer or two it would then defeat the purpose of the hard mount, like a standoff would.

Perhaps if shimming (fine tuning) the aircraft, the best solution is to hard mount the engine to 1/4 or 3/8 aircraft plywood soaked in resin or CA to harden "fuel proof" the wood plate then mount to the exisiting firewall as far out on the corners as possible with precise cut 3/4 - 1" hardwood dowel material with 1/4" bolts, that way if shimming is needed you could just re-cut a slighlty longer dowel on the appropriate sides.

The wood dowels to wodd plate is more likely to absorb vibration over aluminum standoffs with less transfer to the airframe, plus the spread on a 1" dowel really helps.

Just a thought. I may give this a try first. Thanks for all the help. I'll post pic's once I get fabricated. Dan

Hi,
No problem adjusting thrust in any direction. You just have to sand the wood block on a flat table. There's no need to use washers or shims. In fact, I accidently built in too much right thrust into the firewall when I replaced the original firewall. I had to remove a 1/2 degree out of the wood block.
Steve

I have used a similar wooden mount on several large engines including a DA-100. Works very well and holds the engine very rigid. Easy to make with some basic woodworking equipment.

John W.
Scottsdale, Az.