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SunSurfer

TD3 binding plate metal fatigue

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Bomber TD3s are built pretty solidly, "bombproof" construction, the website says.

Yet I've just discovered that my riding style produces significant bending forces on the rear of my rear binding, and over thousands of turns over 4 years metal fatigue and failure finally occurred at the points where the mounting screws go through the baseplate to the cant disk. On my last day in Snowmass after ATC I thought I wasn't riding as well as usual and then I felt an odd "crack" under my rear boot. When I finished riding and the snow melted I found what you can see in the photos.

I've e-mailed Jim Callen and he replied "I see it a couple times a year. It's usually from bigger riders who ride hard, after a couple years of riding them." I'm 182cm and 82 Kg (6 feet, 180lbs approx.)

In a while I'll order a new base plate. The failure is clearly wear and tear. I'd never seen anything on the Bomber Forum about this kind of problem.

So, periodically check your TD3 binding plates for cracks, because, strong as they are, they are not indestructible.

TD3 metal fatigue fracture 01.jpg

TD3 metal fatigue fracture 02.jpg

Edited by SunSurfer
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Interesting, thanks for sharing! Right where the screws hold the plate on both sides. 

I'd say that's something to be proud of as these things don't fail often. :) 

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Disaster barely avoided it looks like. I will check my TD3 step ins regularly now. Thanks for the heads up.

Edited by boardguru

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I have Td2's (3 sets) and ride them hard and it's been more than 10 years on them and no sign of failure.  I'm nut sure if the full inside disc makes a difference on how stiff  they are. 

Glad you are ok and no injuries happened. 

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1. Good that it failed in such a way that you found the problem without injury.

2. The very handy center hole could be smaller and still provide easy access to the center fasteners. 

3. Would be nice to have the option of that same part made of thicker stock. 'Bombproof' is the 3/8 plate I use on my TD1/TD2 hybrids, but 5/16 would suffice.

Edited by Beckmann AG

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I suggested the idea of using more screws to Jim C when I first discovered the problem, in particular a centre screw at the rear of the ring. Jim didn't think it necessary, but I'm weighing up a range of reinforcement options for my replacement base plate.

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Not an engineer but: the strength/type of forces exercised on the plate will depend upon your binding angle it seems. Any binding angle that maximizes the distance between either of the intec heel receiver screws and the plate mounting screws will also maximize leverage acting upon the plate at those screws. Your angles seem to maximize this effect. The angle of the plate cracks seem to run (nearly) perpendicular from the forces exerted by pulling on that side of the intec heel.

You are regular-footed yes? And tall (making your leg a more substantial lever)? So the intec heel mounting screw that is furthest from the cracks is on the lateral side of your rear foot? perhaps caused by driving the rear knee forward during heelside turns and thus pulling on this side of the binding? Internet physics armchair guess ...

 

 

58a807cd6cdfb_TD3metalfatiguefracture02.thumb.jpg.1585f7abbdf79c9f7a599b1a9c450cf1.jpg

Edited by queequeg

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Regular, 60 degrees rear foot, mondo 29 UPZs. Drive both knees, especially the knee on the outside of the turn ( Left knee toeside, Right knee heelside) down towards the carving edge, both toe and heelside. 

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There is a clue wrapped around the front bail. The resilient tape allows the front of the boot to rise off the binding and the back of the boot to rotate down around the two rear screws.  Forget the slot bevels and use a pan head bolt in order to increase the section modulus. May have to offset the heel clip to accommodate the bolt but there definitely needs to be additional material to carry the load. 

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Ran this by some of my friends at work (enginerds)

It's totally possible that repeated bends will cause microfractures in the plate.  Eventually this will lead to catastrophic failure.  

We came up with a couple of solutions:

  1. Make the plate thicker
  2. Use more screws
  3. My personal favorite: Make the plate out of steel (316 stainless feels right)

 

Probably not super helpful but if it happened once it will happen again.   Just out of curiosity I'm running some simulations to see what you can expect for lifetime.   As an engineer I wouldn't ignore something like this.  This time the binding failed safe, next time it could fail catastrophically. 

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Consider failure rates before doing a complete redesign on behalf of Bomber.  If loaded frequently, everything eventually breaks.  It may not be in your lifetime, or it may be tomorrow.  FMEA (google that if you're having trouble sleeping!) can help guide how critical this failure is:

- It's easy to detect a partial failure before anything catastrophic.

- Even after one side breaks, the parts are still held together enough to keep your feet on the board.

- The failure rate is low.  Maybe not by automotive standards (1:1,000,000), but it's reasonable for a low-production snowboard binding.  

This is one plate out of many hundreds, that broke in a nice progressive fashion, after a long service life.  The crack would be visible to the naked eye.  

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Tape around front bail is over 1mm thick PVC tubing. The toe shape of my UPZs contacts a naked TD3 toe bail at just 2 small points. The tape/tube is significantly more worn at those 2 points but the effect overall is to spread the toe loading over a larger area.

The toe bail of my F2 Intecs fits UPZ boots like a glove!

When I order a new base plate I will be ordering extra screws for attaching my base plates to the cant discs. 

Edited by SunSurfer
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Ultimately this is Jim and Angie's call.  I'm not going to redesign anything unless they actually ask me to. (I would be glad to help though)

 

Problem is that they know about failures like this.  To quote from the first post: "I see it a couple times a year. It's usually from bigger riders who ride hard, after a couple years of riding them.".   God forbid somebody gets hurt they might be held culpable (it's not like people like to sue for things around here right?).  While I agree that FMEA is a good tool for making design decisions it will be hard to use it as a defense against a lawsuit. Granted this isn't a medical device but it might be worthwhile to consider a fix as due diligence.     

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On 2/18/2017 at 3:44 AM, SunSurfer said:

I've e-mailed Jim Callen and he replied "I see it a couple times a year. It's usually from bigger riders who ride hard, after a couple years of riding them." I'm 182cm and 82 Kg (6 feet, 180lbs approx.)

I'm only reacting to the picture and the quote.  To fix the problem either reduce the inputs OR become robust to them.

A couple times a year over a low volume indicates a higher than (1:1,000,000) failure rate.

 

stress-strain.jpg

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2 hours ago, erazz said:

 

  1. Make the plate thicker

 

56 minutes ago, SunSurfer said:

...extra screws for attaching my base plates to the cant discs.

BTDT, works great. 

td3.JPG

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I should add that you shouldn't be afraid to ride TD2s or TD3s.   In my opinion they really are "Bomb proof".   They are solid and well constructed.

My concern is more towards Bomber themselves.  Since this has been brought up so publicly they should not ignore it as it opens them up to any greedy lawyer.   

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I had a similar break a few year ago, but in my case one of the screws was obviously loose. I figure the break was just a side-effect of the flex that the loose screw made possible, so I just check those screws more often now.

SunSurfer, where were the screws installed when the break happened? I'm guessing they were right where the cracks formed, but that's just a guess...

I've always wondered whether it's better to try to put one screw right at the heel piece (as close as possible), or have it supported by one screw on either side (twice as many!). 

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Nate, they were right where the cracks occurred. I had almost always ridden that binding at 60 degrees,  regular stance, cant disk and binding plate axis aligned (no cant). The screws were always tight, never found them loose after riding. 

Our collective impression that TDs were unbreakable gave us a false sense of security. This event should reset that. I don't blame Bomber for this, but I am of the belief I have a personal responsibility to keep an eye on my equipment. That may reflect my Kiwi mindset and a completely different tort law environment in NZ.

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(Disclaimer: I'm not a Bomber employee, but I do own and like a lot of their products.)

If anyone wants a binding that will have zero field failures, it's very possible. But it'll be heavy and expensive. Some already think the TD3 is too far towards the durable/heavy side of the equation. 

You could go to the other extreme and buy some other brands that are known to break under larger riders. 

I inspect my stuff fairly regularly and accept the low level of compromises present in the TD3s.  

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TD3 heavy metal.1493367003595-1747790277.jpg

Base plate might just be indestructible now.

Edited by SunSurfer

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I've experience a similar baseplate failure before. Mine sheared near the heel like your's did. 

FYI, I only use the long baseplates now. They are beefier around the toe and heel due to being longer overall and wider in the toe and heel areas. 

The long baseplates are somewhat of a secret item. They were never available on the website store. Only available by request. I don't know if they have any in stock or are still making them at this point.

+1 for long baseplates! Jim, please keep making them for us big guys!!!

Edited by heroshmero
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Generally speaking, slot-head machine screws are for low-torque applications, (and the toe pad sandwich looks a little prone to going walkabout),  so keep an eye on them for stretch.

I'd send you a thicker plate, but alas,they're all drilled to the TD1 standard.

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Toe pad spacer is also made from the broken TD3 baseplate. The threaded holes in it have been drilled to 6mm so that the screws go directly into the baseplate. Unless the screws loosen I don't think it's going to wander. Thanks for the heads up on the slot head screws, will source hex head countersunk screws of the appropriate length for heel & toe.

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