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  #1  
Old 03-15-2009, 08:48 PM
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Webb Webb is offline
 
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Location: Jackson, MS
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Default Correcting engine sag

I've noticed that my engine has dropped about a 1/4 inch. After reading posts about how to raise the engine, it appears there are 2 basic ways to accomplish this. Put the washers between the bottom mount and the engine or between the firewall and the engine mount.

Is one method better than the other?
Is one easier than the other?
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  #2  
Old 03-16-2009, 04:58 AM
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Brantel Brantel is offline
 
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Default

When you really study this issue, it seems the engine does not drop at the front so much as it drops straight down parallel to the thrust line.

When you add washers, you are changing the thrust line.

A friend of mine fixed his by switching from the Van's to the Lord mounts.


As far as your original question. it would be much easier to put washers behind the mount to the firewall than to mess with the engine bolts. This puts some stress in the mount though.
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  #3  
Old 03-16-2009, 05:59 AM
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f1rocket f1rocket is offline
 
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Default

I would advise against putting washers between your engine mount and firewall. The accepted method is to swap the washer around on the engine mounts themselves, or replace your mounts with stiffer ones.

Given the variability in putting these things together, I doubt seriously you'd have to worry about the thrust line changing, but I'm not an engineer.
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  #4  
Old 03-16-2009, 06:55 AM
wv4i wv4i is offline
 
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Default Q on bottom engine mounting bolts

Engine sag? Even if not, a Q check on the bottom engine mount bolts (to firewall) is not a bad idea.
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  #5  
Old 03-16-2009, 07:13 AM
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bhester bhester is offline
 
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Location: Hopkinsville, KY
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Default Are you sure?

Webb, are you sure you have the correct rubber mount s in the correct location?

The reason I ask is two fold, mine has about 280 hrs. and it has not sagged at all. I do loops and rolls in it also. The other reason is because I heard from a buddy that a couple guys at his airport put theirs in the wrong location because the local "expert" told them wrong and their engines have sagged.

I don't have the instructions in front of me but I am thinking that the ones with the washer molded in goes on the bottom. Check the instructions to make sure.

I'm using the mounts that Vans sent me.
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Last edited by bhester : 03-28-2009 at 10:55 AM.
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  #6  
Old 03-16-2009, 07:26 AM
Roger Moore Roger Moore is offline
 
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Default Weldments

My engine droop in my RV4 was caused by broken weldments,so that is a good place to start. Roger Moore
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  #7  
Old 03-28-2009, 06:01 AM
rgarrett7 rgarrett7 is offline
 
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Location: Clifton, VA
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Default

I added a couple of extra washers on the engine mount. I cut slots slightly larger than the bolt into the washer. This let me install the washers by sliding them on over the bolt without removing the nut. I just loosened the nut and used a engine hoist to raise the engine. Still painful to get at the nuts, but at least I did not have to pull the bolts and get them restarted through the dynafocal mount.

Definitely raised the engine up.

I had about 500 hours on the engine before I noticed that sag. It gradually got worse until I put in a couple of washers per side at 800 hours. I now have 850 hours. I do regular aerobatics, including 3g loops.

Randy
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  #8  
Old 03-28-2009, 07:30 AM
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Webb Webb is offline
 
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Location: Jackson, MS
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Default

Quote:
Originally Posted by bhester View Post
Webb, are you sure you have the correct rubber mount s in the correct location?

The reason I ask is two fold, mine has about 280 hrs. and it has not sagged at all. I do loops and rolls in it also. The other reason is because I heard from a buddy that a couple guys at his airport put theirs in the wrong location because the local "expert" told them wrong and their engines have sagged.

I don't have the instructions in front of me but I am thinking that the ones with the washer molded in goes on the bottom. Check the instructions to make sure.
Positive - I checked them about 15 times before I hung the engine. All 4 are the same. Top and bottom are oriented differently.

Ironically this post showed up this morning. The wife is out of town, it's raining, and I was looking for something to do. Washers showed up in the mail yesterday. Hmmmmm....somebody trying to tell me something here?

It's not a bad drop but it bothers ME. I talked to Ken at Vans and his comment was it wouldn't change the thrust line enough to effect flight characteristics. It is more "cosmetic" in nature and effects the builder's temperment.

One thing for sure, if my airspeed goes up, is was needed. If my airspeed remains the same, it was cosmetic. If my airspeed goes down, I'll jerk 'em out and live with the drop. My guess, it's cosmetic. I'm flying to Atlanta tomorrow and will report back any changes.
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  #9  
Old 03-28-2009, 08:38 AM
n721dp n721dp is offline
 
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Location: Fayetteville, Arkansas
Posts: 24
Default Engine Sag

I have the same problem on my -6A.

It has been suggested to me by a DAR to shorten the stop tubes inside the top set of mounts since this is what you are torqueing the bolts against.

I haven't done it yet but it seems logical.

Dave Gehle
Heber Springs, Arkansas KHBZ
RV-4, RV-6A, J3-C65 (in pieces)
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  #10  
Old 03-28-2009, 09:52 AM
chaskuss chaskuss is offline
 
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Location: SE Florida
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Default Lord, Barry or VIP mounts used????

Bobby, Randy and others,
Please edit your posts to include what brand (and model if you know it) of mounts you are using. This will aid those who have not decided what brand of mount to buy.
Charlie Kuss
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