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KS 16S Pedal arm bolt snapped already!


mrelwood
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6 minutes ago, mrelwood said:

I replaced all 4 bolts with good quality stainless steel ones. The M8x35 is not a standard size, so I did have to cut them from slightly longer ones.

Smart idea! Did the remnants of the sheared bolt extract easily?

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Just now, Rehab1 said:

Smart idea! Did the remnants of the sheared bolt extract easily?

Surprisingly easily. I was able to rotate and screw it out just by prying with a flathead screwdriver. Could've been a tough job.

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23 minutes ago, mrelwood said:

Surprisingly easily. I was able to rotate and screw it out just by prying with a flathead screwdriver. Could've been a tough job.

Wow you’re lucky. I envisioned you using an easy out extractor.

Edited by Rehab1
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The design could be better.  It needs alignment pins or shoulder bolts. The threads pass from on piece to the other. This allows movement.  A shoulder bolt with the shoulder passing from the cap into the arm and then changing to thred would reduce movement.  Alignment pins would be even better. 

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Glad you did not take a dive and hurt yourself, have got no idea bout measurements but curious if there may be enough thickness to drill out and re tap for M10? Mostly curiosity but high quality M8's should be more than enough. I made a spiral stair case at work today and all bolts except for those connecting the stairs to the center pole is stainless M8's in different lengths, alloys, models,  center pole connections a single M10 for each step and designed for a lot more weight, force than a wheel will ever see no matter how it's ridden. So while should not be a problem perhaps peace of mine is a good thing to, I suppose if wanting to take it further one could machine new pedal arms from a high tensile strength Titanium alloy block and bolts but not everyone have got access to that through work and quite costly to order such a job if paying for it yourself so must do the best of a given situation.

I am curious though, is the pedal arm design of all King Song wheels?

Should anyone have this happen to them and bolt cannot be extracted with easy just Google screw/bold extractor, avoid the cheap china copies go for the real deal and remember that drilling speed formula is different for stainless vs for example carbon steels, lower rpm and preferably quality HSS Co bits + punch a center to start in to avoid drill slippage and "eating" into to the Aluminum alloy as well as avoid going hard with worn low quality bits in stainless or will just heat it up getting tougher and tougher to get through.

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11 hours ago, mrelwood said:

There is some space, but I wouldn’t take anything away from the aluminium. As you said, proper quality M8 ss bolts have no problem carrying the rider’s weight. It’s the quality of the original bolts that I blame, I wouldn’t weaken the current design.

The first ride with the new bolts and I did crash though! Not because of the bolts but wet gravel trying to swallow my wheel. Thank goodness for protection, I’d be pretty torn without. And last night when going for a ride, the tire was flat from the crash! Fixing it today. Murphy has a focus on my EUC riding all of a sudden.

Got it and yes agree, good thinking to get them yourself instead of ordering KS own bolts in your case having broken once and probably more convenient too so win/win.

Ouch, glad your ok and again fully agree, I leaned the hard way to not be stupid and ride without my wrist protection and took me away from my job for 3 months.

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Makes me wonder if I should replace the bolts on my KS's, but then I'm lightweight, and this is the first time I've heard of such incident... Some earlier KS's did suffer from poor quality pedals, but there the pedal itself developed cracks, instead of the pedal hanger/frame/whatsitcalled. 

The hanger pieces themselves aren't really complicated parts, wonder if anyone has a "real" CNC that could machine those out from some sturdier material? ;) Start a small side business making spare mechanical parts for wheels... :P 

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My first though was that I must alert every possible 16S owner and strongly encourage them to replace the bolts... But as you said, this is an extremely rare issue, with several circumstances that must have aided the bolt to snap.

But then again... the bolts cost me 4€, and the quality, heft and authority of the new bolts really is at a very different level.

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Yes, some work and a low cost, even if not even necessary see it as a cheaper semi insurance of sort, at least potential part insurance

 

Absolutely Esaj, casting is not the right way to go, machining out of a block for sure the way to go, anyone happen to have got some decent 3D print equipment at home with 3D scanner, alternatively a stand alone scanner and of course a pedal arm to scan?

Ti 6AL-4V ELI and start chipping off? ?

 

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20 hours ago, Electroman said:

Yes, some work and a low cost, even if not even necessary see it as a cheaper semi insurance of sort, at least potential part insurance

Will have to see, I do have some M8's laying around, but not sure of their quality and don't remember if they had hex sockets... could still be better than the originals, though  ;)   No go, they're hex-bolts (not hex-socketed) with large heads and only 20mm. Have to pick up some longer ones some day. If anyone wants to go overboard, there's stuff like these: https://racetechtitanium.com/index.php?main_page=product_info&cPath=33_34_37_45_81&products_id=3749&zenid=acf224072eb34f807df95df9ce6d959d  (M8x35 Titanium Bolt (DLC Coated) - Aerospace Grade Titanium - CNC Machined - Heat Treated - Rolled Threads), only $4.99 per piece :D 

Quote

Absolutely Esaj, casting is not the right way to go, machining out of a block for sure the way to go, anyone happen to have got some decent 3D print equipment at home with 3D scanner, alternatively a stand alone scanner and of course a pedal arm to scan?

Ti 6AL-4V ELI and start chipping off? ?

Yeah, it's overkill, but then again, people are more likely to have a CNC than metal casting equipment in their home  ;)  Although, real CNCs (that can machine larger metal parts) are very expensive, so that kind of people are few and far apart, and likely the part cost would be pretty high  :P 1RadWerkstatt sold custom pedals at one points to some wheels, I believe those were machined from solid aluminum blocks, but they cost something like way over 100€ per pair.

Edited by esaj
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1 hour ago, esaj said:

Will have to see, I do have some M8's laying around, but not sure of their quality and don't remember if they had hex sockets... could still be better than the originals, though  ;)   No go, they're hex-bolts (not hex-socketed) with large heads and only 20mm. Have to pick up some longer ones some day. If anyone wants to go overboard, there's stuff like these: https://racetechtitanium.com/index.php?main_page=product_info&cPath=33_34_37_45_81&products_id=3749&zenid=acf224072eb34f807df95df9ce6d959d  (M8x35 Titanium Bolt (DLC Coated) - Aerospace Grade Titanium - CNC Machined - Heat Treated - Rolled Threads), only $4.99 per piece :D 

Yeah, it's overkill, but then again, people are more likely to have a CNC than metal casting equipment in their home  ;)  Although, real CNCs (that can machine larger metal parts) are very expensive, so that kind of people are few and far apart, and likely the part cost would be pretty high  :P 1RadWerkstatt sold custom pedals at one points to some wheels, I believe those were machined from solid aluminum blocks, but they cost something like way over 100€ per pair.

Yeah this is true and good point, casting's more on the larger, cheaper fabrication side. Even if not even having access to the full automated CNC there always alternative like semi manual methods like basic cut out using water jet, plasma and heck even machine cutting, milling etc only imagination put the limits on. Not something we have laying around at the company I work for but if doing a job with correct sized left over pieces that could be a fun little project, ok good information I had no idea but like you hint at in regards to custom pedals 1radwerkstatt sold, the cost...

I don't think I would buy the Alu block either to start machine my own, even if cost was only my own  time, quite costly considering the size of the blocks but well worth it if getting them free of charge as well as free access to the machine park, even though the company have got no CNC atm, sister company have got one I think but so long ago I don't even remember AutoCad? ?

 

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  • 2 months later...

Parking stuff in TME for next order, I remembered to check for these bolts, if anyone's looking for them:

https://www.tme.eu/gb/details/m8x35_d912-a2/bolts/kraftberg/

Screw; M8x35; DIN:912; Head: cheese head; imbus; HEX 6 mm A2-stainless steel

Was thinking I could order some myself just in case, the minimum order quantity is 100 pieces @ 0.1544€/piece (with Finnish 24% VAT), totaling 15.44€, so not that bad, but... what the hell am I going to do with 96 more M8-bolts? :P 

There's also acid resistant A4 -ones at 0.2181€/piece, but again minimum of 100 pieces:

https://www.tme.eu/gb/details/m8x35_d912-a4/bolts/kraftberg/

 

EDIT: Probably better to order zinc-plated bolts, see the post below

Edited by esaj
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20 hours ago, esaj said:

Parking stuff in TME for next order, I remembered to check for these bolts, if anyone's looking for them:

https://www.tme.eu/gb/details/m8x35_d912-a2/bolts/kraftberg/

Screw; M8x35; DIN:912; Head: cheese head; imbus; HEX 6 mm A2-stainless steel

Was thinking I could order some myself just in case, the minimum order quantity is 100 pieces @ 0.1544€/piece (with Finnish 24% VAT), totaling 15.44€, so not that bad, but... what the hell am I going to do with 96 more M8-bolts? :P 

There's also acid resistant A4 -ones at 0.2181€/piece, but again minimum of 100 pieces:

https://www.tme.eu/gb/details/m8x35_d912-a4/bolts/kraftberg/

316, or A4 as it is referred to here have got a few % Molybdenum in it and just slight different mix of Chromium and Nickel, for that alone I'll go with the 1/4 extra in price and you can say: I have got Molybdenum in my darn pedal thingys!  :lol:

..on a serious note, tensile strength is serious business for both, pick any one and be real happy Esa.

 

 

 

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26 minutes ago, Electroman said:

316, or A4 as it is referred to here have got a few % Molybdenum in it and just slight different mix of Chromium and Nickel, for that alone I'll go with the 1/4 extra in price and you can say: I have got Molybdenum in my darn pedal thingys!  :lol:

..on a serious note, tensile strength is serious business for both, pick any one and be real happy Esa.

I was thinking more about what mrelwood said above about the galvanic corrosion, rather than pure tensile strength, but in the end post-poned the decision further and didn't order either ;) Also because I was in a hurry to pick my components, because my friend was doing an "emergency" order for some more components after running out, and "piggy-backing" on the order I could save on shipping costs ;) So I spent a few feverish (literally; I've been having a flu since last Friday with my fever going up and down each day) hours to think of everything I might need  :P

Never paid much thought to galvanic corrosion before, but yeah, put a galvanic pair + electrolyte (water) together, and you have a small "battery":

EdNdX.gif

Looking at that, using any type of (unplated) stainless steel bolts with (unknown type of) aluminum alloy might not be that good an idea ... Zinc-plated looks like it would be best (unless you can get beryllium bolts? ;))

Edited by esaj
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19 hours ago, esaj said:

I was thinking more about what mrelwood said above about the galvanic corrosion, rather than pure tensile strength, but in the end post-poned the decision further and didn't order either ;) Also because I was in a hurry to pick my components, because my friend was doing an "emergency" order for some more components after running out, and "piggy-backing" on the order I could save on shipping costs ;) So I spent a few feverish (literally; I've been having a flu since last Friday with my fever going up and down each day) hours to think of everything I might need  :P

Never paid much thought to galvanic corrosion before, but yeah, put a galvanic pair + electrolyte (water) together, and you have a small "battery":

EdNdX.gif

Looking at that, using any type of (unplated) stainless steel bolts with (unknown type of) aluminum alloy might not be that good an idea ... Zinc-plated looks like it would be best (unless you can get beryllium bolts? ;))

Sorry to hear that, hope you beat the flu soon and get better.

This is true indeed, good point and especially Aluminum can be specifically tricky in that regard, but since Aluminum we see is always as alloys it's also about what that alloy consist of outside the Alu base, but yeah ground rules do exist for sure, DIY water cooling computers we all know we should not mix those Copper and Aluminum blocks for that very reason. I have good experience with Stainless and Aluminum at least in some regards though, basically each time we cover emergency stairs on the outside of a building (should not see through more than 3 floors) we put down Stainless screws to fasten the Aluminum tread plate , standard 5 bar sheets in 3/5 thickness and AW5745 114 quality we cover with, but yeah that one have got pretty good corrosion resistance to begin with and I do not know what quality the pedals are made from, or what alloys these China manufacturers use where even the naked eye can pick up on lots of impurities and this cloudy or rough look they have got.

Anyway I can confirm this type of Aluminum alloy do indeed work pretty well with 304, , if you go zink treated I would suggest the hot dip galvanized variant, the electroplated variant (although different methods exist) is used even by some car manufacturer etc but in our standards we are not to use it in outside environments and any other steel treated or not could have for ex 1 year warranty, hot galv 5 years, the stainless 20. Just for reference, especially if demands say C3 rating corrosive, coating or higher we must really follow everything to a te but if not and small jobs for private folk or whatever honestly one does not have to go overboard. Besides for these wheels ow many of us go over say 4-5 years with a wheel? Even if one do just do a visual check up now and then and be happy with stainless is my advice. I have on occasion been told on places like for ex  Sweclkockers (computer nerd forum) about how to do my job and what work every now and then cause someone read some theory but just extracted worst case scenario out of it,  but would not worry too much about corrosion unless planning to constantly be in water + some oversight every now and then can be good.

No promises but I could have look what we have in the workshop if you want, if finding some I can send them no problem, I just don't want to promise in case I cannot deliver but I sure can have a look.

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1 hour ago, Electroman said:

No promises but I could have look what we have in the workshop if you want, if finding some I can send them no problem, I just don't want to promise in case I cannot deliver but I sure can have a look.

No need, I'm not overly concerned of snapping the bolts, as I'm lightweight, and to my knowledge, @mrelwood does a lot of off-road riding, unlike me. Thanks for the offer, though  :)  

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Just now, esaj said:

No need, I'm not overly concerned of snapping the bolts, as I'm lightweight, and to my knowledge, @mrelwood does a lot of off-road riding, unlike me. Thanks for the offer, though  :)  

No problem, if you change your mind just holla at me and I'll have a look for sure.

 

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21 hours ago, esaj said:

No need, I'm not overly concerned of snapping the bolts, as I'm lightweight, and to my knowledge, @mrelwood does a lot of off-road riding, unlike me. Thanks for the offer, though  :)  

Whike the pedal /axle mechanism with clamping the wheel is a lot better than on other brands...it still has a small weakness.

And thats that the bolts should be a bit bigger...Because of the -relative- weak aluminium pedal arms, over a long time, 8000km here, the bolts might have got some movement and break in the end.

WHEN something happens over such a usage time, from expeience, its that the bolt is -again- over long time making the pedal arm aluminum even a bit weaker, and getting drawn out of the arm.

But we are talking here about 8000km....i have done 800km on one of my other wheels...and just recently it has to be repaired as the pedal arm/ axle construction got totally bonded inside...new shims now-again...and i doubt this will hold longer than for the next 500-800km.

My point is: the perfect pedal arm construction has still to be found...

Edited by US69
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Hmm, extrapolated I'm doing 4500 km per year on my 16S. 

So I'll reach that 8000 km threshold at least in october 2019. Do I have to worry about my pedals and/or bolts, axles and so on?  :unsure:

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6 minutes ago, Borg666 said:

Hmm, extrapolated I'm doing 4500 km per year on my 16S. 

So I'll reach that 8000 km threshold at least in october 2019. Do I have to worry about my pedals and/or bolts, axles and so on?  :unsure:

Naaah, not in General. What definitly will help from time to time is to maintenance a Wheel...check the axle bolts etc etc

My Point was just that even this -allready very good construction- still has a bit of a weak Point...

That all has also to be seen not only in Kilometer. Depends on riding style, weight, tire pressure and maintenance, too!

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The fatigue limit can also be hard to calculate when the load is neither constant or at the same level at all times + the metal also behave differently depending on what climate we ride in so I suppose become more of a guessing game for us mortal men?

I ride Gotway so not the same but those pins holding the pedal enter my mind every time I go up/down a curb or unexpectedly hit some uneven surface in the road a bit too fast, it's true I carry a bit of weight and a 60 kilo rider have less to this about. At least his fatigue limit would be set much further into the future, then again I would never keep riding for years and years without replacing them no matter what weight and how I ride my wheels, it's just common sense they must be replaced at times if keep ticking up kilometers/miles and better to replace them too often than the other way around.

It's so easy to stand on the wheel though and think, ok I just applied a bit of pressure on the pins, but if realizing the speed I kept and my weight and start thinking about the forces at play me too start to think about different solutions, or force these thoughts away from my head and try to think about chocolate cake or something to take my mind of it.

Agreed US69, I take it further and claim the perfect solution will never even enter the market or even be thought up, besides it will also always be a compromise but hope to see someone really clever just get one of these flash ideas and just see the simple, sturdy yet lightweight and cheap solution in front of him/her and make it happen? Multiple solutions superior to any brand out there can be thought up I have 0 doubt.

Just curios, where does that 8000km limit come from, did someone calculate a a number from a heavy guy riding in a abusive way in some aggressive environment and then just apply it over the board (which would mean a light guy riding soft in a temperate environment would make it much further), does the manufacturer recommend or what? Would love to try to talk some of the software guys at work, one of the designers keyboard in a set of parameters into the program and let it start a calculation, just for general idea even though it would never hit some exact magical number for every man out there but still it would be a number and, after all it's good for load carrying structures where people lives are at stake but so again those always exaggerate something crazy and cannot add so much extra materials to these pedal arms without bulk and weight, materials though..

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