[Closed] Some engineering help please

photo?

I found hammering in a larger Torx bit gave me enough purchase to turn the thread out. Sadly that wont help you now but for anyone reading with a similar problem try that!!!

How far into the threaded hole did the drill stay central before it shifted off course?

Pics would be good

I took this (not the best pic ever) t.co/NwEbFMI3

could you get a longer bolt and use a nut and washeron the end?

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OMFG! (eek, sorry about the size!)

wow, that drilling really went off didnt it..

If it was mine I would just pop the bolt in and ride it see what happens.

You can fill it for cosmetic reasons if you wanted, not sure how much extra strength it would add though.

You could perhaps get it welded up but it will bugger the threaded hole and by the time you have machined it etc will prob be an expensive fix.

Yup it sure did!!! So called mechanical chaps did it.

Hmmmmmmmm,,,,,

I presume that pic is upside down?

On the one hand the shock is pushing towards the weakend side of the mount, on the other hand circles tend not to crack, so if it lasts the first few rides it's probably OK.

Not sure whether liquid metal would work or not, whatever you used would have to be stiffer than the surrouding aluminium. Tthe porper way to do it would be to thread the new 3mm hole, insert a steel theaded rod in and grind off the ends, then drill out the original eyelet and re thread it. That's going to be hard though as the drills going to want to slide away from the steel rod (and into the aluminium) as it's harder than the aluminium.

An even better way would be to go cap in hand to Giant and ask if they'll sell you a new one from warrenty stock?

Who did the drilling, Stevie Wonder?

I'm not an engineer but by some of the comments preceded by 'I'm an engineer' I've heard and read, that sometimes doesn't mean a lot! )

If the direction of shock force under compression is in line with the hole, as it looks to be, I think it'll crack between the eyelet hole and the drilled hole and open out the eyelet sooner or later. Metal filler may help if prepped properly, I don't know how effective it'll be in supporting the eyelet against opening out - I'd say it's terminal from that pic.

One thing you could try / consider as well as metal filler for the hole is to bond a steel bush inside the hole to reduce the stress on the eyelet next to the hole, and fit a bolt that works with the bush, you may need to step the bolt down in the bushed area but that itself may be a stress point that fails under shear force.

An even better way would be to go cap in hand to Giant and ask if they'll sell you a new one from warrenty stock?

I've already asked them for a new bolt, so I don't want to take the piss.

whatever you used would have to be stiffer than the surrouding aluminium.

I'm don't think this is a good idea, better to put aluminium in the hole. Dissimilar compliance leads to stress concentrations.

If you are going to put steel anywhere then in the eyelet hole would be the place.

If you have access to the tools a good ish idea might be to mill out the eyelet to a much larger dia to include the new hole and then thread, bond a steel insert into the big hole and drill & thread that.

did you pay some one for this? they should probably pay for a new one.

3mm in piece how thick?

3mm to bottom of taper I assume?

Buy a new link. You'll need one once it cracks so why risk face and frame in the meantime?

wow.. good luck with that.

Is that hole right thru? Its a horrid bodge for sure but I would probably ride it.

the only thing that will make a significant difference is to fill it with weld and re drill / tap the hole

If you have access to the tools a good ish idea might be to mill out the eyelet to a much larger dia to include the new hole and then thread, bond a steel insert into the big hole and drill & thread that.

Did the 3mm drill hole go all the way through the arm, or just kiss it, hard to tell from the photograph?

Buying a new arm might be your safest option.

3mm to bottom of taper I assume?

Is it tapered? I hadn't noticed that.

That's a good ides, but I'd ask Giant first if you can just buy one, it'll be a lot cheeper.

Yup I agree, I'm only suggesting bodges in the absence of a replacement... I don't think anything will be as good as a new one..

If it's drilled, there will be a taper on the end of the drill... Drills aren't flat.

doh, yes sorry, I assumed it was a through hole. Unless it was done with an end mill..

thisisnotaspoon - Member

"If you have access to the tools a good ish idea might be to mill out the eyelet to a much larger dia to include the new hole and then thread, bond a steel insert into the big hole and drill & thread that."

That's a good ides, but I'd ask Giant first if you can just buy one, it'll be a lot cheeper.

It won't add a lot of strength back in - just remove stress risers and even out the loads

There is no way the Drill 'Started off straight' and went off at that angle! Thats an impressive **** up! Sorry not helpfull.

Possible to have someone fill it via Ali welding? I.E just pool a load of ali weld in there. Then re thread?

Honestly buy another. Like someone said if it would withstand forces as it is. The manufacturers would drill holes like that to save weight. As they don't and they haven't i would assume it's unsafe.

If it was a friend who did it for you, slap him and tell him to buy you some beers! Lots of it!

If it wasn't a friend get them to buy a new one for cocking up.

Woah lots of responses!!! I have rang Giant to tug on their heart strings and they are being very helpful. I am waiting out to see if I need to buy a new one or not.

[url= http://www.toolstation.com/shop/Power+Tool+Accessories/Speciality+Drills+Chucks/Screw+and+Bolt+Extractor+Set+5+Piece/d80/sd1400/p51010 ]Bolt Extractor[/url]

PS, for future Bolt Extractors are good.
Drill a small hole slightly down the centre, Extractor has a course thread that grips and remove that way 😀

Teej what how are you defining strength?

I just dun a friday afternoon spesh as I thought this was interesting, unit load in the y direction, from bottom to top, no fill, alu filler, steel filler, and finally steel big insert. I have hidden the filler in the 2nd and third models to show the diff between the strains around the two holes.

Its a bit bollocks as they are bonded together so the alu fill model might as well just be the original unadulterated item. There are a few other holes in this model too but its just to illustrate.

Results are strain.
Worst is no fill, best is big steel insert. Although this does not account for the fact that the bonded interface between the inserts and the parent part will likely be the failure . I have to actually get back to work now.

Edit last pic show the holes filled ina nd you can see the diff between the steel fill (top) and the alu fill (middle)

[IMG] [/IMG]
[IMG] [/IMG]
[IMG] [/IMG]

Bolt Extractor

PS, for future Bolt Extractors are good.
Drill a small hole slightly down the centre, Extractor has a course thread that grips and remove that way

That's what I though they were doing!! Clearly not!!
Will buy some for myself.

The problem with bolt extractors is they're had as f***, and consequently brittle, get it ever so slightly wrong and you end up with an aluminum part, with a steel bolt in it, with a hardened steel extractor in that, good luck drilling that mess out afterwards!

thisisnotaspoon - I fully agree! In this situation the Bolt i belive was not stuck but just rounded. but in any case with an exctractor i would get some WD or similar down the thread incase it has seized at all.

But yeah i agree, there not Great, but there good enough if your gentle with them.

WOW!!!! Giant strike again!! They are sending me a set of rocker plates that they had kicking about there warehouse. Ok they may be white (mine are black and my bike is silver) but at least I have them.
What a company!

Awesome!

Result!

Hole doesn't go through? Less of an issue then. Even less if you got a new part )

I think you should make whowever drilled the old one wear it on a string around his neck as a mark of shame.

Toys - my thought was as you would be reducing the amount of alloy in the piece then it would be weaker - does your analysis consider it as one piece not two stuck together?

My thought would be the alloy would deform around the steel bush as there would not be much of it

best is big steel insert. Although this does not account for the fact that the bonded interface between the inserts and the parent part will likely be the failure . I have to actually get back to work now.

Indeed - the alloy could deform and the bond fail

tbh I would have thought the part would have been fine just left. Not messed with any more with fillers or inserts or anything.

I am guessing the bolt tightens up into that part clamping the inner part of the bush between 2 of those plates?

If so the load should be carried from the friction on the faces not the threaded part.

Andyl that would be correct if the bolt had a head on one end and a nut on the other, but on the trances I have seen it threads directly into one side (and I have assumed its the side we are lookign at, in which case the load is shared between the threaded area of the flange and the inner face in contact with the bush. But given that the dia of the bush face will fall inside/onto the "extra hole", when the load is transferred to the flange the extra hole will make a difference. Might need to draw this...

man i miss solidworks 🙁

If you did have to try and bodge it, which you dont have to now. I would of got a metal rod cut to the right depth for the hole but slightly larger OD and hammered it into the hole and then ridden it! Saves having to use liquid metal that wont set in the same way.

Plus, thats why I ride Giant!

I can honestly say I am gob smacked at how Giant have helped me out. I own a Defy road bike as well and.... I will be buying Giant again should I need a new bike. I am sending the warranty guy (think it was John, I am hopeless with names) some stuff as a thank you (he doesn't do booze).

'kin hell!!! It arrived today!!! 😯 How's that for service 8)