Safety Wire

[Pokey Paul]

Howdy,
I'm sure this is a real newbie question, but does anyone have any info on how to correctly install safety wire? (Rules section 3.7.2.2 "-Correctly installed safety wiring")

I understand the basic idea as described in http://www.geocities.com/robm351/pantera/index-24.html but I'm wondering if it's possible to safety wire 1 bolt? My team is planning on using a single bolt and a threaded insert for the rear suspension rocker arm. Since the other allowed locking mechanisms tend to deal with the nut, I assumed that basically my only other option would be to use safety wire. The only problem is that when there is one bolt, there is nothing for it to tighten against.

Thanks for any help,
-Paul Daman

[Pokey Paul]

Well here I am replying to my own post...
Never mind, A couple links down from the pantara diff site on google was:
http://www.ultralightnews.com/pilotslounge/safetywire.htm

I swear I looked about a month ago and couldn't find anything of the sort.

Sorry for the waste of time...

[Buckingham]

Machinery's Handbook (Amazon.com)

[jack]

god damn i hate safety wire http://fsae.com/groupee_common/emoticons/icon_mad.gif

i think "tune to win" has some stuff about safety wire, make sure you get the proper gauge wire, i was going to use .02" wire, but although the FSAE rules dont say anything about it, this size wire is illegal in most racing, .05" is a little big, so find something in between.

[Jonathan D]

if you have something you can "tie off" the safety wire to, then yes, you could probably safety wire one bolt.

the problem with a rocker arm is that you won't really have anything nearby to tie off to, without cross over the rocker.

[Buckingham]

Instead of using safety wire you could try using filler rod. And instead of twisting it you could try melting it between the nut and the bolt. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[jack]

....hahahaha

also, i try to design to have a nut on a bolt if i can, so instead of safety wire, you can just throw a ny-lock on.

[Travis Garrison]

Hey Jack...I just took apart the suspension to shim ____ could you safety wire it back up for me?

-Travis Garrison
UW FSAE
WWU Alum.

[Charlie]

Safety wire is best. However there are nylon-impregnated locking bolts, 'stover' (deformed thread) bolts, and of course loctite for those rare blind holes that must be secured.

[Courtney Waters]

True, true. Though, like Carroll Smith says in just about any of his books, if it's been safety wired that's usually a pretty good indication that someone has properly tightened the faster when they installed it. Other than that, Charlie's listed methods are a lot less frustrating http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Pokey Paul]

Yeah, the problem with this application is that you can't really get at a bolt head, so the lock nut is out. Welding a threaded rod is a no go (safety wise) so it's looking like safety wire.

Thanks for the input.

-Paul

[johnnySV]

when choosing safety wire size i recall three common sizes: 0.02X", 0.035ish", and 0.04X"

i prefer the 0.035"ish. the smaller is a bit too delicate, and the larger is just plain thick.

Pokey, i am having trouble picturing you setup; if u post a pic of what you are trying to constrain, that might spark a solution

[DougMilliken]

Originally posted by Pokey Paul:
http://www.ultralightnews.com/...ounge/safetywire.htm (http://www.ultralightnews.com/pilotslounge/safetywire.htm)


From the link:
"Use the cutters in the jaws to cut the safety wire to the proper length, then bend the end of the wires over so that you don't poke yourself on them the next time you reach into work on something."

Most of the safety wire I saw at Michigan was nicely done, but some had sharp points left exposed. While judging semi-finals I managed to cut a finger on wire next to an upright (it's dark inside the wheel). Nothing serious, but distracting none the less. Pros all take the extra second to bend the sharp ends out of reach.

[Bemo]

Hurting a design judge won't improve your design score http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[Chapo]

Cut away safety wire and just use locking helicoils http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Tech Guy]

Matt,
Locking helicoils don't cut it with the tech inspectors!

[DougMilliken]

Locking helicoils don't cut it with the tech inspectors!
Equally bad idea to cut the tech inspectors<grin>! The safety wire that bit me was (iirc) locking a large diameter nut.

[Chapo]

Ill bite here, why don't locking helicoils cut it with the tech inspectors?

In the rules it says that positive locking mechanisms must be used and provides a list of what is included as a positive locking device (it is not exhaustive). Locking helicoils that are made to the appropriate milspec/ISO standard are acceptable in aviation as a positive locking device, they are just as effective as a metal lock nut, and I would even say more effective than a nyloc especially in elevated temperature applications. In light of that I don't see why they wouldn't be considered as an appropriate positive locking device for FSAE.

Thats my interpretation and 2c

[Nihal]

The response I was given when I asked many years ago about using a locking helicoil in a blind hole application was that they could not inspect whether the locking portion of the threads were engaged with the bolt sufficiently.

[Chapo]

I can see the concern, but that same level of unknown can exist with other positive locking mechanisms as well. Say people re-using nylocs, this 100% shouldn't be done, but people will still do it, and they become absolutely useless after a few applications. How do you then police that? There has to be a certain amount of trust between the judges and the teams that things are done correctly.

Also with regards to the locking portion of the threads being engaged, for a 1/4" locking helicoil the locking threads begin literally three threads down (about 1/8"). Regardless of weather a blind hole had a locking helicoil or was just tapped and then safety wired I would expect more than three threads to be engaged in the material. If there were not enough threads used to engage the lock, then that bolt and hole assembly is dangerous (susceptible to pulling out) no matter what is used as a positive lock.

I'm not trying to jump up and down until I get my own way here, I'm just curious to see what other people think.

[moose]

Your point is far, but that line is tough to draw.

Do you say that restrictors shouldn't be tested either? That's just a trust issue, certainly not for safety...right?

I agree that there is trust that teams used nylocks correctly, but I look at those rules in 2 lights.

1. Safety - don't want to see wheels flying off, throttle cables coming loose, etc.
This is why the rules requires that everything on the tech sheet is visible..so that it can be confirmed to be as safe as is required to the best of the inspectors' abilities.


2. Self-preservation - if you design / assemble things so that it might fall apart, guess who feels the most pain? yup..and I'm sure this is why you're comfortable with locking helicoils. If you want the xyz part to stay on, you of course locked the bolt. So this is where the layer of trust comes in with nylocks - yes you used them, "did you use new ones".."of course" -That's all that can be asked as a tech inspector, but you're trusting the team will be smart.

There are plenty of teams that would lie and say "of course it's positively locked" just to get through tech, while there is very little incentive to re-use a nut other than cost/time. It can easily be changed before/during/after tech with no impact on getting through.

Certain dangerous designs are impossible to see, but the idea is to minimize the possibility of them. If teams are incentivized to use nylock nuts with 2 threads showing, it ensures there isn't a 2-thread in a blind hole situation. Sure they could have that with safety wire, but a helicoiled hole could be locked, could be loctited, could have 2 threads engaged.. just too many variables.

that's my 2 cents at least..

[Luniz]

The thing is, those regulations exist for a reason. So if there is a connection which needs a "positive locking mechanism" according to the rules, you actually don't want it to come loose as a Team or driver.
My Team DNFed last year in Hockenheim because the scruitineers didn't spot that our diff wasn't lockwired. After we "got away" with it in scrut, we just couldn't be asked to do it anyway, we've been lazy. Guess which bolts came loose in endurance...

[Fantomas]

Probably I do not get the sarcasm (Why is there no sarcasm smiley?) in your post, but why should the scrutineers be responsible for your DNF? Furthermore the diff is nothing that has to be checked by the scrutineers according to the rules.

Fantomas

[Luniz]

You kind of got me wrong on this, or I got something wrong with my english... I am in no way saying that the scruitineers are to be blamed for our DNF! I just wanted to illustrate that the locking rules are there for a reason and every team should lock all possible bolts in their own interest. Otherwise it can result in a DNF.

I think the connections on the diff and if they have to be secured is kind of debatable, in the rules it says that every "critical bolt" is to be secured. If you consider the diff to be critical is your own decision, or the decision of the scruitineer.

[Fantomas]

I think the connections on the diff and if they have to be secured is kind of debatable, in the rules it says that every "critical bolt" is to be secured. If you consider the diff to be critical is your own decision, or the decision of the scruitineer.

Critical is related to safety in the rules not to reliability in my opinion, otherwise every screw would need a safety wire...more or less http://fsae.com/groupee_common/emoticons/icon_smile.gif

Fantomas

[Chapo]

@Moose
Don't get me wrong I wasn't suggesting that the scruitneering should be based on a trust system. All I was saying was that there is some implicit trust involved in the process with things like locknuts.

I also think that if locking helicoils are used proof of purchase should be provided, much in the same way that it is required for composites in the chassis.

The point that I was making with regards to the safety wire is that if a bolt is installed in a blind hole and there are not enough threads to engage the locking section of the helicoil then there isn't enough threads engaged for the bolt to be safe even with a normally tapped hole that is lockwired. Any fastner that only engages two threads in prone to be ripped out.

The only variable here is whether or not the hole has a locking helicoil in it, which can then be satisfied with the team providing proof that they have purchased sufficient quantities of helicoils, or undoing the bolt to show the colour of the helicoil (pink is reserved for locking coils for ease of identification) and then re installing the bolt.

They just make design so much easier.

Regards

[moose]

As a piece of design, simplicity, keeping it clean, etc. I'm with you. And yes, having no threads engaged is impossible to see from the outside and a disaster waiting to happen.

I just think for the path we're all on and the purpose things serve, it's a situation where things would be hard to change. I just felt the need for someone to play devils advocate more than anything (beyond quoting the rules).

[Michael Royce]

If you look under the Frequently Asked Questions (FAQs) on the official FSAE web site at:
http://forums.sae.org/access/d...f/folderFrame/100090 (http://forums.sae.org/access/dispatch.cgi/fsae_pf/folderFrame/100090)

you will find # 83 at:
http://forums.sae.org/access/d...Securing%20Fasteners (http://forums.sae.org/access/dispatch.cgi/fsae_pf/docProfile/100176/d20081029212535/No/B.14.2.1%20Securing%20Fasteners)

which says:
“B.14.2.1 Securing Fasteners
Based on a couple of recent questions, the Rules Committee has decided that in order to be consistent, we need a clearer definition of what constitutes a “positive locking mechanism” as required by Rule B.14.2.1.
The definition we will apply is as follows:
1. The Tech Inspectors (and the team members) must be able to see that the device/system is in place, i.e. it is visible.
2. The “positive locking mechanism” does not rely on the clamping force to apply the “locking” or anti-vibration feature. In other words, if it loosens a bit, it still prevents the nut or bolt coming completely loose.

Also, “prevailing torque lock nuts” fabricated by a team will not be acceptable. We have no certainty that they will have the quality control to work all the time.”

This was first posted in December 2006.

Finding the FAQ’s on the official SAE web site has become rather tortuous, so I suggest you all bookmark it! They are at:
http://forums.sae.org/access/d...f/folderFrame/100090 (http://forums.sae.org/access/dispatch.cgi/fsae_pf/folderFrame/100090)

To get there from official FSAE web site at:
http://students.sae.org/competitions/formulaseries/
go to:
“Forum” in the top left hand box,
then to:
“Rules Discussion” on the left hand side just under “Formula SAE Public Forum”,
then to:
“Frequently Asked Questions” which is at:
http://forums.sae.org/access/d...folderFrame/100090/0 (http://forums.sae.org/access/dispatch.cgi/fsae_pf/folderFrame/100090/0)

In fact it is easier from the Formula Student web site, where if you look under “Rules” at:
http://www.formulastudent.com/...ts/FS2011/Rules.aspx (http://www.formulastudent.com/events/FS2011/Rules.aspx)
and click on “FAQs” gets you to:
http://forums.sae.org/access/d...f/folderFrame/100090 (http://forums.sae.org/access/dispatch.cgi/fsae_pf/folderFrame/100090)

The Rules only require positive locking on the critical fasteners on the steering, brakes, suspension and driver’s harness. If fasteners on the diff or driveshafts come loose, the tech inspectors don’t really care, you just come to a halt! However, smart teams will put locking fasteners on them too.

In the past, FSG has banned the use of Nyloc nuts on brake calipers. I have not seen a problem with this usage in the past, and I notice that they have deleted that ban for 2011.

[Chapo]

Cheers Michael,

I didn't even know that those forums existed.