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Old 12-30-2018, 07:47 PM   #1
dmurphy
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Default Help! Lug bolts just snapped!

Holy cow ... This is awful, just awful.

I just put new tires on my i2 SE, and after torquing on the wheel to 25ft-lbs (at least according to my torque wrench) - just testing it out in the garage, the right wheel just snapped right off! All 3 lug bolts just completely snapped. Simply unbelievable.

Could you imagine if this had happened out at speed? I'd be in a world of trouble.

So a couple of things ...

#1 - any suggestions on how to replace the lugs? It seems they're press-fit into the triangle plate. Anyone been able to replace them successfully, whether by heating the plate or ...?

#2 - Now I can't trust the left side either!

I checked the manual and torqued to 25ft-lb of torque - see the wrench.

http://www.segway.com/media/1603/i2_..._and_wheel.pdf

How could I have possibly snapped these bolts? And more importantly, how do I fix them? Anyone have a suggestion on someone who's experienced in such things? I really don't want to drop $1000 on two new transmissions - I may as well scrap this thing instead. Seriously, what a disappointment.





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Old 12-30-2018, 08:51 PM   #2
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Hate replying to myself, but ...

Removed the left side and the bolts there are compromised as well! How could this have happened? I had the torque wrench set to 25ft-lbs. Did I really over torque it to the point of snapping 6 bolts? How can that be?

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Old 12-31-2018, 12:30 AM   #3
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Did you have a tough time getting the nuts off the first time that maybe the studs fractured on removal then fractured even more on installation?
I'm sure those studs can be replaced but there might be a lot of disassembly required.
Give a good repair shop a call and bang their ear a little. Maybe you can do the bull work and let them replace the studs in the hubs. Maybe these guys? http://segwayofannapolis.com/
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Old 12-31-2018, 09:13 AM   #4
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Quote:
Originally Posted by truck View Post
Did you have a tough time getting the nuts off the first time that maybe the studs fractured on removal then fractured even more on installation?
I'm sure those studs can be replaced but there might be a lot of disassembly required.
Give a good repair shop a call and bang their ear a little. Maybe you can do the bull work and let them replace the studs in the hubs. Maybe these guys? http://segwayofannapolis.com/
That is whatís so dang bizarre. I had no trouble getting the nuts on or off. Smooth as silk. And in fact, when I took the left wheel off (the one that remained attached) - the nuts came off easy as pie, exactly as I wouldíve expected in a normal situation. Very bizarre. I might have to call Tony Stark and apply for a job with the X-Men or something - maybe I have superhuman strength and just donít know it.

I found a used pair of gearboxes on eBay for a reasonable(ish) price so Iím going to change them out. Weíll see what kind of condition the couplers are in but Iím thinking a full gearbox replacement is the only safe way to do this .... unreal.
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Old 12-31-2018, 09:59 AM   #5
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I likely have that torque wrench. 10-75 ft/lbs clicker type.

Those bolts do look stretched. Could someone else have over torqued them during servicing? Hitting it with an air impact wrench? Could they have stretched when the wheel was loosely tightened down and still ridden?

A precision measurement equipment lab I used to work with would often throw out torque wrenches for being out of tolerance and not being economical to fix. Out of tolerance torque wrenches are common. Could yours be rusty or binding inside the torque wrench?

But, I figure you would have noticed the over torque you applied when it started hurting your hand more than usual.

I am betting that someone else over torqued it during previous servicing. Maybe tightening it down again and again as the nuts came loose during test driving.

Note, you have to clean off the rust on the mating surfaces to get an accurate torque. You have to take a wire brush to it. Otherwise, the rust binds it up early when torquing and then grinds down during use, thereby leaving the fasteners loose. I lost a wheel off my rusty car this way when I was young.

Repair is just getting a machine shop to press in new studs. Or a car shop. hub might need to be removed from the gear box.
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Old 01-01-2019, 12:05 PM   #6
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Iím not a metallurgist, but I donít see evidence of internal failure. That is, donít see any evidence of cracks, internal rust, etc. Havenít seen any other reports of this failure, and Iíve been following SC since 2006.

Given that all six bolts failed, it would seem that the issue is specific to the individual machine. It is possible that some unusual process, such as hydrogen embrittlement or galvanic corrosion could be a factor. The hubs look corroded, but there is a lot of clean grey steel showing in the bolts, and 25 lb-ft isnít that much torque. Occamís Razor points to overtorque.

Maybe contact Segway about this. If I were Segway, Iíd want to take a close look at those bolts, in case something is occurring over time in the field. If so, maybe theyíll send you some new hubs in exchange for your failed parts.


Questions: 1. How old is the machine? 2. Why are the hubs so dirty/corroded? 3. After snapping off one or two bolts, why did you proceed with the rest of them?
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Old 01-01-2019, 02:29 PM   #7
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To question three: His post indicates that he installed the wheel after changing a tire. The nuts were tightened and everything seemed okay to take a test ride. During the test ride, the lugs snapped and the wheel came off.

I would take his torque wrench to the same machine or auto shop he is getting to press in his new bolts. Get them to compare how the position of a tightened 25ft/lbs nut with their torque wrench to what position his torque wrench puts it.
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Old 01-01-2019, 06:20 PM   #8
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Quote:
Originally Posted by Civicsman View Post
Iím not a metallurgist, but I donít see evidence of internal failure. That is, donít see any evidence of cracks, internal rust, etc. Havenít seen any other reports of this failure, and Iíve been following SC since 2006.

Given that all six bolts failed, it would seem that the issue is specific to the individual machine. It is possible that some unusual process, such as hydrogen embrittlement or galvanic corrosion could be a factor. The hubs look corroded, but there is a lot of clean grey steel showing in the bolts, and 25 lb-ft isnít that much torque. Occamís Razor points to overtorque.

Maybe contact Segway about this. If I were Segway, Iíd want to take a close look at those bolts, in case something is occurring over time in the field. If so, maybe theyíll send you some new hubs in exchange for your failed parts.


Questions: 1. How old is the machine? 2. Why are the hubs so dirty/corroded? 3. After snapping off one or two bolts, why did you proceed with the rest of them?
The machine is, I believe, 5 years old. I did buy it second hand, but itís an SE model. Thatís where the corrosion is from as well - itís all surface rust. I believe (but could be wrong) this was a tour machine used in Greece. Thatíd explain some of the salt air surface stuff going on. Nothing thatíd concern me about integrity, all just surface stuff.

The bolts snapped when I was taking it for a test ride after changing the tire. If it had happened when attaching, Iíd absolutely have stopped.

I think Iíll reach out to Segway corporate since this seems so unusual. Consensus seems to be a complete gearbox replacement is necessary - even a machine shop wouldnít be able to help - thereís not enough clearance behind the backer plate to install new studs without removing it from the gearbox itself. Just not enough depth.

I have a pair of used gearboxes on their way - hopefully theyíre in good shape. Weíll find out the hard way. :-)
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Old 01-06-2019, 12:32 AM   #9
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Well, here's the update ...

Received the used gearboxes yesterday ($290 for the pair on eBay), and got a little time tonight to install them.

Lookin' good! We are back in business. The replacement gearboxes are doing wonderfully; they were in perfect condition and actually seem a little "tighter" than the originals. Rocking forward/backward, I hear a little less gear lashing; they just seem like a little bit of an upgrade.

One thing I did notice is that I'm going to need elastomers at some point. The existing ones are still OK but not perfect - one in particular is starting to get slightly sticky and has a little bit of small shaved bits. But that's a project for another time. I'm sure I can do a teardown/gearbox replacement much quicker next time now that I've been through it.



Now, to analyze what happened .... I borrowed a buddy's torque wrench and mine is definitely defective. So I'm sure I overtorqued the bolts - I definitely muscled it trying to get the torque wrench to release. When I used my buddy's, it did so with very light pressure. I didn't realize how little pressure 22 ft-lbs takes.

So yup, I over torqued with my defective wrench.

Anyway - here's two photos of the left and right gearboxes. You can see one still has intact but compromised studs. The other one is the one that sheared off while testing the unit after replacing the tires last week.

Now, the bigger problem is that I can't just replace the studs without disassembling the entire gearbox. As you can see, there's not enough clearance to press the lugs out of the rear of the carrier plate - it'll hit the transmission housing. So even if I took it to a machine shop, there's nothing we can do without opening the gearbox, which is a task I really don't want to do.



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Old 01-06-2019, 02:17 PM   #10
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Beautiful machine and many thanks for giving us closure on the story of the snapped bolts. I'm glad you were able to get a set of clean and tight used gearboxes from eBay.
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