Can’t get engine mounted

[spinningwrench]

I have been trying for two days to wrestle my engine into the mount but the misalignment is just too great. It behaves as if the bushings are too thick. I have tried three different techniques as outlined in the RV builders forums but with no luck. Part of the problem may be the large weld fillet pictures here which prevents the isolation mount from fully contacting the flat portion on the interior of the welded mount. I have run this by Bob via Mark but they don’t think it is a problem. Any thoughts?

[Utah-Jay]

Took me 5 hours to get mine mounted. Spoke to Mark, and then Bob.

My top mount holes were 3/8’s too wide. I asked Bob if I could ratchet strap it and he said go for it. I cranked on that ratchet and finally got it. The BH (Dynafocal) mounts area pain.

I too used the very good RV instruction page.

Good luck

[spinningwrench]

So are you saying you actually deformed your engine mount as supplied to make it work?

[Utah-Jay]

I flexed it to get the bolts inserted

[gregc]

I basically did the same thing - I let the engine weight flex it vertically and a ratchet strap to flex it horizontally. That plus a drift pin and a lot of patience eventually worked.

[Paul Johnston]

Attach the mount to the engine first,then swing it onto the airframe after. This way the mount can be sprung as it’s fitted to the engine- the mount is correct.

[spinningwrench]

I tried this. The mounting holes for the engine are way off, a little horizontally and a lot vertically, about 1/2 bolt hole. You shouldn’t have to deform the engine mount that much to make it work. I have had two experienced A&P’s helping me for a couple hours and they have never seen one this difficult

[Paul Johnston]

The Berry mounts are much more flexible than these. It’s Been a couple years since I did this , the forth mount was a WTF moment - it’s so far off- Ithink I pried between mount and engine - maybe some fowl language too! But in the end it was ok.

[svyolo]

I am not sure which way is easier, I only did it one way. The mount was already attached to the engine. I did have to "spring" the mount to match up with the holes. One of them significantly but it didn't surprise me that much, and it didn't seem that hard to do. I used a chain hoist, and I think I got the three upper bolts in first, then "did what it took" to get get the lower bolts in. There are lots of ways to tweak the mount. Bar clamps, ratchet straps, etc.

[rodsmith]

I believe the engine installs are more difficult on the O-360 mounts. I built my own O-540 mount. When installing the engine 4 of the 5 holes lined up great, the upper right was off by half a bolt hole, didn't take much force to pull it into line.

[Steve W]

Try with three bolts in place (two in bottom and one on top) almost tight or loose enough to move the bushings towards the center focal point with force if they can move. Lift engine more to push against the one remaining hole. The little bit of distance you get from tightening up the three might make the difference to start the fourth one.
I had a Wicks ring that used the small bushings. I had to make up a set of aluminum bushings to simulate the mounts to straighten it out. I’d never purchase another welded one. Better off to buy the pieces and weld it up yourself.
This might be repetitious cause I haven’t read what’s suggested on the RV forums.

[spinningwrench]

Thanks, I can’t even get three bolts in they are so far off. Based on others having to use ratchet straps there likely may be a problem with the mount. I’m hopefully will be able to check it against a weld fixture on Friday.

[Bcone1381]

I went through what Spinning Wrench is going through. I thought my mount was wrong. After talking to Mark I refused to believe my mount was defective. I finally got it using ratchet straps, creative hoist tricks and a small bullet to align the hole driven by the bolt.

If you had difficulty too but we’re finally able to wrestle it on then say so.

Doing this for the first time not knowing adds to the difficulty and doubt.

[jaredyates]

When I first got 303AP I replaced the rubber isolators. It was a bear getting the engine back on, and that was a case where I knew the mount was right because I had just removed the engine from it. I remember it was hard getting the 360 mounted on our first plane but I think I only had to do it once.

[spinningwrench]

As a follow up I took my engine mount to American Champion aircraft today, (builders of the Citabria). They did indicate that the mount should go on with little effort if built properly. They use the Type I dynafocal routinely. Installing the mount with a lot of force ie ratchet straps, alignment pins, etc is a bad idea as it puts a lot of residual stress in the mount.

[Battson]

I flexed it to get the bolts inserted

How much force was required? It sounds like a great way to increase the risk of fatigue cracking in future, if a lot of force was used. Sometimes things do settle in though. To check it, I would suggest taking a bolt out once the engine has been test run, and see if the mount springs out of place, or if it stays put.

Mine went on easy as - everything lined up perfectly. I could also remove a bolt without the whole assembly moving.

Are you sure you have the right rubbers, correctly fitted? Photos would help if you were interested in any advice. But it's your call.

Try with three bolts in place (two in bottom and one on top) almost tight or loose enough to move the bushings towards the center focal point with force if they can move. Lift engine more to push against the one remaining hole. The little bit of distance you get from tightening up the three might make the difference to start the fourth one.

^ This sounds like a good idea to me. Keeping the bolts really loose and starting at the bottom.

Getting ready to install (again):
IMG_20171025_183553.jpg

Engine in place:
IMG_20171028_183844.jpg

Close up view:
IMG_20171028_143345.jpg

[spinningwrench]

Thanks for the reply. We have already determined that our motor mount is defective as we can only get two
bolts in at a time. I had no more luck when I took it to American Champion Aircraft where skilled assemblers who mount dynafocal engines every week were unable to make it work. A conversation with Bob indicates the bolts should go in with very little force required. I agree that using a lot of force is asking for trouble down the road as fatigue cracks in the mount could easily develop. So today I started the new weldment for the motor mount. It’s an interesting 3D challenge but I should end up with a nice fit.

[Battson]

A conversation with Bob indicates the bolts should go in with very little force required.

That sounds more like it. Engine mounts across all kinds of aircraft are prone to cracking anyway, without spring tension introduced to the frame.

[spinningwrench]

I’ll put some closure on my frustration with my engine mount. I got the Aircraft Spruce Dynafocal ring mount in today. It mounted in 5 minutes with absolutely no pressure required to insert the bolts. In addition it is a more substantial weldment with better clearance around the accessory case. I also really like the way they formed the Dynafocal rings as they are are perfectly flat surface to mate with the rubber isolators. Now to complete the rest of the mount. Both Bob and American Champion confirmed that the mount should not require any force to install. I think it is urban legend that mounting an engine should be difficult.