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-   -   RV-12: Engine Mounting Cap Screws Inspection (https://vansairforce.net/community/showthread.php?t=65020)

dick seiders 12-06-2010 12:19 PM

Feedback from Van's call today on torque question regarding the amount of torque added or subtracted when using the ball allen wrench angled to the head of the bolt:
Use the amount the Rotax manual calls for. (360 in lbs.). ie: the difference due to angle of wrench has negligible impact on torque applied.
Dick Seiders

rschy 12-06-2010 03:55 PM

Just what I thought
 
Quote:

Originally Posted by dick seiders (Post 491303)
Feedback from Van's call today on torque question regarding the amount of torque added or subtracted when using the ball allen wrench angled to the head of the bolt:
Use the amount the Rotax manual calls for. (360 in lbs.). ie: the difference due to angle of wrench has negligible impact on torque applied.
Dick Seiders

There you go..... "Use the amount the Rotax manual calls for. (360 in lbs.). ie: the difference due to angle of wrench has negligible impact on torque applied." Just what I thought, but I'm sure there's some here that think they're smarter than the Van's engineers. For those I have a bridge in Florida you might be interested in.

vernhendershott 12-06-2010 06:02 PM

Quote:

Originally Posted by rschy (Post 491376)
There you go..... "Use the amount the Rotax manual calls for. (360 in lbs.). ie: the difference due to angle of wrench has negligible impact on torque applied." Just what I thought, but I'm sure there's some here that think they're smarter than the Van's engineers. For those I have a bridge in Florida you might be interested in.

Yes, that would be the same Van's engineers who told us that leave the powder coat, 312 foot pounds and just the split ring washer would be just fine.

They, just like us are human and from time to time make a mistake, we have all learned a lot on this one and each will take what we have learned and do what we think is correct and safe.

I just hope Van's can get past its sever NIH (Not Invented Here) issues and get back to what is safe for their customers.

Best regards,
Vern

yankee-flyer 12-06-2010 08:24 PM

I'd agree
 
As an engineer, I'd agree that the angle (very small) of the ball driver in the cap head screw has a negilgilbe effect on the torque-- the torque lost due to the angle is probably under the level of the accuracy of most of our torque wrenches and certainly less than the breakout or drag torque of the bolts. You could check the torque OK with the ball driver but there's no way you can get that bolt out to add Loctite without removing the drip tray. My O-ring came out of the manifold side but went back in OK.

Marty, who is "LEAF"-- Lockwood??

Thoughts on cleaning old Loctite frombolts? Wire brush in a dremel/ Acid bat" Somethnig in between??

Wayne 120241/n143WM
Now Loctited and 360 in-lbs.

Mel 12-06-2010 08:28 PM

LEAF
 
"Leading Edge Air Foils" is a Rotax service center.

jersey 12-06-2010 08:29 PM

Thanks Larry and Marty
 
I think everybody including Van's should thank Larry, Marty and all the others for stepping up and posting the original notices that warned of the bolts comming loose. Im afraid that Van's might not have caught it in time. There were several out there that actually lost a bolt or two. I don't think it is productive to ridicule some one for researching potential solutions to the problem. We are after all building experimental aircraft with no track record. I think we would should encourage each other to step forward with ideas and thoughts and not rely solely on Vans to take care of us. That is the purpose of the forum after all. Critical thinking is something that appears to be rare these days. Personally I have gleaned a lot of knowledge and have been impressed with amount of research that has taken place. I don't mean to step on toes but sure want to encourage my fellow builders to keep their findings and observations comming in. I truly believe that a tragedy may have been avoided.

Gary Eldridge

MartySantic 12-06-2010 08:55 PM

Quote:

Originally Posted by yankee-flyer (Post 491477)
As an engineer, I'd agree that the angle (very small) of the ball driver in the cap head screw has a negilgilbe effect on the torque-- the torque lost due to the angle is probably under the level of the accuracy of most of our torque wrenches and certainly less than the breakout or drag torque of the bolts. You could check the torque OK with the ball driver but there's no way you can get that bolt out to add Loctite without removing the drip tray. My O-ring came out of the manifold side but went back in OK.

Marty, who is "LEAF"-- Lockwood??

Thoughts on cleaning old Loctite frombolts? Wire brush in a dremel/ Acid bat" Somethnig in between??

Wayne 120241/n143WM
Now Loctited and 360 in-lbs.

Using the equation I presented a few posts ago, with a 20 deg angle (I went back out and measured it), with 360 in-lbs dialed in the torque wrench, 338 in-lbs is delivered to the head of the capscrew. Insignificant. I do not know. But I do know Van 's is telling us that an increase from 310 in-lbs to 360 in-lbs should or may resolve this issue. Is 338 in-lbs OK with a ball end wrench with the 20 deg angularity? Time will tell. Measurement inaccuracy exists either way. The force to loosen is highly dependent on this preload.

I did not use the ball end. Was much more confident removing the drip pan and getting a straight shot at the capscrew. My replacement o-ring should be here tomorrow. And, you are correct. To remove the capscrew, the drip pan has to be removed anyway.

The Loctite data sheets indicate cleanup with MEK and a wire brush.

http://www.loctiteproducts.com/tds/T_LKR_BLUE_tds.pdf
http://tds.loctite.com/tds5/docs/243%20NEW-EN.PDF

LEAF is Leading Edge Airfoils out of Lyons, WI, one of the major ROTAX USA repair facilities. Ordered the o-ring from them!!

Suggest getting a current catalog from all 3 of the major repair centers. Just ordered and received one from CPS, California Power Systems. A lot of good ROTAX info. The other is Lockwood in Florida.

Thanks for the GOOD feedback from all of you guys. And no matter what, please continue to list any findings here with respect to the RV-12 as all of us continue to learn. Do not allow anyone to suppress your thoughts. If right, GREAT. IF wrong, so be it. BUT, we all learn! (I have to remind myself of the same every so often).

Geico266 12-06-2010 10:28 PM

Final Posting Rant By OP.
 
Well said Gary and Marty.

While we may have been lulled into a false sense of security with the "build it to the plans" mantra, it is clear as experimental aircraft builders we are on our own at times. The "plans" only go so far, this forum goes all the way. This thread / this forum stands as testament to that ideal. Thanks to all who make that possible, DR & the mods you know who you are! ;)

Vans has detailed what needs to be done to modify the cooling shroud and re-torque the 4 engine mount ring bolts. My assumption (along with Pete) is that ends their responsibility. While I hoped it would be more, in retrospect it is enough. They know what they are doing and this is their sandbox. Lets "trust" their judgment, "but verify" from time to time. ;)

My only regret is that I did not sound the alarm 6 months ago when I found the bolts loose. I thought I screwed up and did not tighten them properly to begin with. If someone would have gotten hurt or worse because I did not recognize the problem (see original post, THANK YOU TONY T!) and let everyone know sooner, ....lets just say I'm glad no one got hurt. Lesson learned.

This is why I love experimental aircraft. To build, to fly, to be a member of VAF & EAA. It is the constant learning, understanding the process, materials, engineering, and people involved in experimental aviation, and being humbled by the knowledge of others. :o A finer bunch of men and women there is not.

Thank you one and all who have contributed to this thread and posted the results of my initial inspection request. The inspection results you posted helped sound the alarm and get the word out as fast as possible, and I owe you a cold one. I tip my hat to all of you who lost bolts and were brave enough to post it here (at the risk of ridicule) to help sound the alarm louder and clearer. Thank you!

DonFromTX 12-07-2010 06:51 AM

I would like to echo the thanks, from all of us who have not even started to build, and will have things like this very important problem discovered and solved long before we even see our engine for the first time, by those with the courage to go first. I feel like I have 75 personal test pilots out there working for me.

yankee-flyer 12-07-2010 08:05 AM

Thanks to EVERYBODY
 
I think the value of this forum has been more than amply demonstrated once again. Larry, I think any of us would have made the assumption you did, that the problem was a personal error, not a design issue. In retrospect, it's hard to believe that such critical bolts are not saftied in any way (hindsight is great, but we do have 70 years of aeronautical "good practice" to draw upon), but none of us recognized that as an issue.

I'd really like to know if the red prototype (and Mitch's New Blue) have powdercoated engine mounts??

You guys in warmer climates keep checking those bolts! It's going to take a while to get another 5 hours on 143WM.

Thanks again

Wayne 120241/143WM


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