Scored Walls?

[MrGrey]

I recently was drilling in to the 2X2 keel of my gyro and mildly nicked the inside wall of the tubing when a drill bit broke... it is about 1/4 inch in length and barely nicked the inside.... is this something that is going to be of terrible consequence? It seems as though it was very mild in nature but not sure if i should take the whole gyro apart or live with it.... Is it also feasible to maybe strengthen the area by mounting a 1/4" plate clamp to strengthen the area?

[M. Pearce]

MrGrey,
I'm no expert by a long shot but I think someone would have to see this one to give you the Green Light. You know it's one of those things that you and only you can be resonsible for in the end. Get someone to look at it for you in person if possible. Is it too late to get another piece of aluminum and do it over? Is it a double 1"x2" mast? And did you file the edges smoothe?


Mark P.

[Bob]

personally I believe way too much SPOTLIGHT has been put on "scoreing the Walls" of a tube .... if its a minor scoreing Imyself would give it no thought at all. if however you drilled the hole into the wall itself then yah I'ed replace it ...but from what you discribed its a nick..... big deal ! as long as you didn't destroy the metals integrety its still a piece of metal !
... the prefectionest attitude would tell you when in doubt replace it ! .... but I would say What for !
Sure ...metal can fatague at a slight nick and a crack could start and the whole aircraft brake in half ! .... now i ask you ...is that very LIKELY to happen in your lifetime ?
.....
if your worried about a minor scoreing I'ed say step back and look at what your building ... its not a rocket ship for goodness sake .... it doesn't have to be PERFECT ...it just has to work and be safe too....
Gyros are typically too weak to be safe in the first place , in my opinion... so build it STRONG and do away with the worry !
.....
You already Know that a nick in the wall can cause problems
or it may never even bother it .... the choice is yours
I would refrain in adding a plate clamp on the airea for weight purposes... even a little extra added weight will push you over the limit....
....
if it were mine I'ed use it anyway ! but thats me !
My gyro is built alot stronger than most too and it looks like heck to be quite honnest ! ... but I am not afraide to get in my gyro eather... it won't fold up arround me if I make a silly mistake .... you can't say that about most ultralight gyros !
......
what I'm saying is .... its doubtfull you hurt the metals striength by a silly nick in the wall of the tube .... with a nick you have the worry of a crack starting at some later date... MUCH later date .... that will probly never occure in your lifetime ! even with all the vibrations these little things can produce .... just check it from time to time and don't forget !
....
thats my opinion, and I'm no expert..so use your own judgment !

c ya
Bob.....

[banaari]

Umm - a dissenting opinion.

We are not building go-karts here.
Bob, it might not be a rocket ship but it's still an aircraft.
If something breaks, it will probably fall out of the sky. And the pilot dies.

From small nicks, bigger things start. Given the nick is on the inside where you CAN'T inspect it easily, in a structural member... then if it was me, and if I was the slightest bit unsure, and I couldn't get someone (knowlegable and experienced) to look at it, I'd replace it.

regards,
John

[karlbamforth]

Originally Posted by Bob

Gyros are typically too weak to be safe in the first place , in my opinion... so build it STRONG and do away with the worry !
Bob.....

Bob if this is your opinion then why allow further potential weaknesses like nicks ?

The best advice here is exactly what Bob says, do away with the worry, chuck it in the scrap bin.

One of the problems with this type of discussion is the terminology. IE. what is a nick? 1 inch long and a 1/4 deep or 1/4 long and 1 thou deep. One is a lot more important than the other but both could be considered nicks.
Is it possible to accurately measure the offending nick and/or post a picture.

[Papa Smurf]

There is no doubt that nicks usually are a bad thing. How much material was moved, location and shape, are players in the stress concentration game that causes fatigue cracks. If installed would this nick be on the top, bottom, or side of the keel? Is it accessible for buffing? (I doubt it).

If only a few thousands deep and you can get to it to polish it some it's possible the tube could be saved. If polishing the main thing is to remove all corners. An area 1/4 inch long, 10 thou deep, 1/16 wide with 90 degree sides is much worse that an area 5/16 long, 12 thou deep, 1/8 wide that gently transitions. Now these numbers are just for illustration purposes and are not to be considered valid for determining if this particular tube is usable.

[Caribean_gyro]

just put it the garbage and do it again. AS besen stated no scoring. this is where the crack will develop. our macines are bending constanly any fault in the structures is asking for troublem

chuckP

[chuter]

Keep in mind he said this nick is in the keel, not the mast.

I would say it just depends on where it is in relation to everything else.

Is it where the keel gets a lot of stress during landing? Or is it in a place that has a lot of other support and not much bending load?

(shade tree engineer talkin' here, so don't put a lot of weight on this opinion)

[MrGrey]

thanks chuter for reminding that this nick is in the keel and not the mast.......if it were the mast I surely would not think twice and re drill it..... to be honest I feel that under my circumstances with a 275 lb gyro and me weighing 160lbs i can afford to add a few ounces of 1/8" plate to clamp the area and strengthen the 2x2

[mceagle]

Originally Posted by MrGrey

it is about 1/4 inch in length and barely nicked the inside....

MrGrey, Just to go against everybody else, I would suggest that if the small nick is as small as you say it is then it should be OK, especially as it is in the Keel and not the mast. I would glue a small bit of wet and dry to a stick and polish it out.

[Mike Schallmann]

I may not have been flying these thing s very long (10 yrs) but I have NEVER seen a 2x2 tube failure that WASNT the result of a CRASH. Take a good look at most gyros if you look closely you WILL find numerous small nicks and scratches -- its a fact of life --now a gouge is another thing --

[Bob]

EXACTLY Mike ! Cheers !

if I believed my gyro would fall appart now or in the future because of a small nick I'ed never get in it !
now granted Prefectionisum has its place but don't take it to the point of being rediculas ! use REASON ! all to often I see posts that urge others to replace a piece of metal because of a nick or burr.... because its in an aircraft ! thats no reason ! it is only a REASON if it weakens the structure of the thing.... and as was pointed out cracks can start where you cannot inspect them... this is very true.... but very very unlikely ! as Mike said and I agree, the only failure of any 2"x 2" alum I have seen has been from crashes.... not every day useage. does that mean anything will pass , of corse not ! you got a head on your shoulders , use it !
... when in doubt Don't ! is a good policy to use in a gyro ! if you doubt any part of your contraption you better fix it !
.... thats the idea I go with on my gyro and so far it has served me well !
I have no doubt that some of you would take one look at my machine and would not attempt to fly it .... its not "Perfect Enough"
Thats fine ! for me it doesn't have to be "Perfect"... I trust it all the same , its got it where it counts !
So what we have is a wide varity of opinions on the subject What is flyable and what is not ! what constitutes a dangerous Nick and what doesn't enters the same way, .....
so it all boils down to your desigon in the end , its your life... will you trust that piece of metal with it ? if not replace it !
Maybe I've worked too long with metal and have gotten used to nicks burrs and cracks ... hard to say !

c ya !

Bob.....

[Doug Riley]

The location of the nick makes a difference. All three of the main tubes on a Bensen-style gyro are cantilever beams. The fulcrum of the beam in the case of the mast is near the seat back. In the case of a rigid axle, it's near the center, and ditto for the keel.

The fulcrum is the point of highest bending stress. Out near the ends, there's far less bending stress. Straight tensile stress is negligible on the keel and axle, and obviously equals a few hundred pounds on the mast. Bending will get you long before tensile failure on any of the three tubes.

As a result, I wouldn't tolerate any scratching or nicking near the center of the spans of the tubes. Near the ends, it's far less critical.

Scored masts have broken; some in flight and some upon landing, during a vigorous flare. Scores on the outside are worse than scores on the inside, but neither should be tolerated at all in a fulcrum area. It's desirable to use clamp-on fittings in these areas , eliminating the holes.

[Brian Jackson]

Doug,
Thanks for that info. I was envisioning the stresses last night after reading this thread. I was thinking to myself that a keel scored at the nosewheel would have lesser impact than if scored at the cluster plates because of the leverage of force imposed. One of the reasons I've been so "anal" about my build is to eliminate guestimating and judgement calls. I have no gyro piloting experience yet and thus am in no position to make a judgement call on building practices. I trust your judgement however and learn from it.

I liked an earlier post of yours regarding overhead sticks where you suggested (and I'm paraphrasing) leaving "feelings" to the poets. My wife wondered what I was laughing so hard about! Nonetheless, on this topic I've heard people say that you'll likely never see a crack from a scored wall in your lifetime. My only response to that is that's very true. Since the length of a lifetime is subject to change without notice, the vast majority of pilots that experience sudden catastrophic failure will probably never notice that fatigue crack.

[robertstodaro]

I dropped my VW Bensen in up to 2 ft. a few times, never touched the keel.

Broke seat support, bent an axle tube, but the keel takes almost no stress.

I would suggest using steel for the supports of the seat, axle and mast though.