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Posted: Feb 11, 2019 at 1:53 Quote
latheboy wrote:
SuperstarComponents wrote:
numeros wrote:
Now we are talking mate Smile

Mech. Engineer also here. I would sort out the bolts issue with titanum ones, with extra longer threads to cover the possible thread issues. Ti bolts M4 have better performance than M5 regural bolts, so only point would be how would the thread hold up.

The idea of the stem was just lurking for a long time in my mind, and wanted to design something that I would like to ride.

Only concer was stiffness, and handling. Will it increase or decrease performance.

Also, I have run a shitload of simulation, and I will take them with caution, and wont allow anyone to ride the stem before I run 10 pieces to all test on my test jigs.

But thanks for advices, really apreciatte it mate, and if I sounded harsh, must have been my deffensive mode on. I am sorry about that.

Only 1xD of threads actually does something, so longer threads won’t help. Titanium bolts are not stronger than high grade steel.

I haven’t looked at the design but I’m worried for the engineering methods being used here so far.

At the end of the day it’s a stem. They are massively over engineered so you can get away with stuff till it breaks. So test test test. Good luck any I’m sure you will work it out

1 x D is for steel, you should use 2 x D for Al.

Not that simple. It also depends what material the bolt is made of.
With a 12.9 bolt, in a soft aluminum alloy, it's more that 2X, in a 7075T5 alloy, it's closer to 1.5X.
A Grade 5 titanium bolt in 7075T6, is closer to 1X.
I don't recall the exact numbers by heart, but very rarely does it make sense to go above 1.5X, as common sense would dictate a lower bolt grade to be specified for a thread in a soft material.

While on paper a Grade 5 bolt is a great solution, reality rarely follows suit, due to the bolt being rather elastic, so it's only loading the first 1X proper, which leaves a lot to be wished for.
Correct lubrication of the thread during assembly, can to some extent limit the issue, but to expect any bike mechanic taking such measures, I'd say is pretty naive, as they don't even have the required lubricants available.
All that naturally assumes all bolts are tightened to the correct torque, using proper calibrated torque wrenches, of adequate precision.....like if that ever happened in a bike shop, or even worse when people are mounting stuff themselves Big Grin

So yeah, good luck with specifying ti bolts that are on the low side, for any safty critical application on a bike.

Magura Smile

Posted: Feb 11, 2019 at 13:24 Quote
Mr-Magura wrote:
latheboy wrote:
SuperstarComponents wrote:


Only 1xD of threads actually does something, so longer threads won’t help. Titanium bolts are not stronger than high grade steel.

I haven’t looked at the design but I’m worried for the engineering methods being used here so far.

At the end of the day it’s a stem. They are massively over engineered so you can get away with stuff till it breaks. So test test test. Good luck any I’m sure you will work it out

1 x D is for steel, you should use 2 x D for Al.

Not that simple. It also depends what material the bolt is made of.
With a 12.9 bolt, in a soft aluminum alloy, it's more that 2X, in a 7075T5 alloy, it's closer to 1.5X.
A Grade 5 titanium bolt in 7075T6, is closer to 1X.
I don't recall the exact numbers by heart, but very rarely does it make sense to go above 1.5X, as common sense would dictate a lower bolt grade to be specified for a thread in a soft material.

While on paper a Grade 5 bolt is a great solution, reality rarely follows suit, due to the bolt being rather elastic, so it's only loading the first 1X proper, which leaves a lot to be wished for.
Correct lubrication of the thread during assembly, can to some extent limit the issue, but to expect any bike mechanic taking such measures, I'd say is pretty naive, as they don't even have the required lubricants available.
All that naturally assumes all bolts are tightened to the correct torque, using proper calibrated torque wrenches, of adequate precision.....like if that ever happened in a bike shop, or even worse when people are mounting stuff themselves Big Grin

So yeah, good luck with specifying ti bolts that are on the low side, for any safty critical application on a bike.

Magura Smile

Yep you are correct, but to be realistic for a through hole for a M4 SHCS are you going to specify a tread depth of 6mm (1.5 x D) and then try and find a SHCS that is the perfect length?
Or would you source the most cost effective length suitable and then spec the thread depth to suit?
Or even through tap the holes and then source fasteners that might be 1.7 or 2.3 x D ?

Posted: Feb 11, 2019 at 13:39 Quote
Don't mind me, this is a bit close to home at the moment.

I have been dealing with an "engineer" lately who has spec a M8 SHCS grade 8.8 at 32mm long.
The guy is an idiot, I ask why we can't use a 35mm long SHCS (standard length) and tap the through hole a bit deeper and he just starts with the BS about calculations and stuff.
It's not even a weight issue.

So now I have to machine the length down on a 35mm to 32mm on a 100 of the bloody things.
Or not tell him and just use 35mm's and tap the hole deeper Smile

I'm sure there are good engineers but I meet a lot who have no idea about the real world.

Posted: Feb 11, 2019 at 14:31 Quote
I feel your pain. Non-standard bolt lengths are a blight.

Posted: Feb 11, 2019 at 14:37 Quote
latheboy wrote:
Don't mind me, this is a bit close to home at the moment.

I have been dealing with an "engineer" lately who has spec a M8 SHCS grade 8.8 at 32mm long.
The guy is an idiot, I ask why we can't use a 35mm long SHCS (standard length) and tap the through hole a bit deeper and he just starts with the BS about calculations and stuff.
It's not even a weight issue.

So now I have to machine the length down on a 35mm to 32mm on a 100 of the bloody things.
Or not tell him and just use 35mm's and tap the hole deeper Smile

I'm sure there are good engineers but I meet a lot who have no idea about the real world.

Don't get me wrong.
I wasn't debating the lenght to specify for the bolt, but rather the minimum bolt length, that will give the maximum strenght, in different material configurations.

Or in short, the point is that the guy above thought he could increase the safety factor by speccing longer Grade 5 bolts in high alloy aluminum, and that I see we both agree is simply wrong.
I just tried to give the guy a chance to figure why....


Magura Smile

Posted: Feb 11, 2019 at 14:46 Quote
secondtimeuser wrote:
I feel your pain. Non-standard bolt lengths are a blight.

Or a weapon against after market parts.
.....but mostly just the work of a daft engineer.

They are in the same class of engineers, that puts a very fine tolerance, as the standard for the entire part, because he's too retarded to figure that it increases the manufacturing cost by an order of magnitude in most cases.

A pretty good argument for birth control!

Magura Smile

Posted: Feb 11, 2019 at 18:17 Quote
That's maybe a bit far, it can be quite useful to be able to walk in to a new job and be able to say "I can cut production costs by 20%" because all you need to do is take some 0s off the drawing!

Posted: Feb 13, 2019 at 3:38 Quote
secondtimeuser wrote:
That's maybe a bit far, it can be quite useful to be able to walk in to a new job and be able to say "I can cut production costs by 20%" because all you need to do is take some 0s off the drawing!

Use for the engineer, not for product, consumer or company, especially if specing longer and larger bolts and the appropriate increase in machining only costs a fraction more.

Thomson may have saved a few pence and a few grams on their stem, but have lost what was once a devoted following for stems and posts, which is now just the few mtbers that ride a fixed post and want to spend more than a dropper...

Posted: Feb 13, 2019 at 9:55 Quote
working on some crowns that allow you to adjust the offset by +/- 10mm

these are the first prototype, next one is gonna have alot of changes. i like these but not very happy with them

Offset adjustable crowns for Dorados I m working on. Boxxers coming next.

Offset adjustable crowns for Dorados I m working on. Boxxers coming next.

Posted: Feb 13, 2019 at 10:38 Quote
Raw machined aluminium is porn.


Just sayin'.

Posted: Feb 13, 2019 at 10:44 Quote
ktm87 wrote:
working on some crowns that allow you to adjust the offset by +/- 10mm

these are the first prototype, next one is gonna have alot of changes. i like these but not very happy with them
Given the forces that are in line with that slot or act about one of those interfaces I would be surprised if it didn't slip eventually if you are clamping the steer tube in there. If you are putting something similar to a flip chip in I suppose it could work out, but the slight bit of play would weird me out. Anyway around you're going to lose a fair bit of stiffness. Also no pinch clamp for the sanchions? I'll be honest the adjustability at that interface sketches me out. Making four different versions with four different offsets seems like it would be the way to go.

Posted: Feb 13, 2019 at 10:52 Quote
taquitos wrote:
ktm87 wrote:
working on some crowns that allow you to adjust the offset by +/- 10mm

these are the first prototype, next one is gonna have alot of changes. i like these but not very happy with them
Given the forces that are in line with that slot or act about one of those interfaces I would be surprised if it didn't slip eventually if you are clamping the steer tube in there. If you are putting something similar to a flip chip in I suppose it could work out, but the slight bit of play would weird me out. Anyway around you're going to lose a fair bit of stiffness. Also no pinch clamp for the sanchions? I'll be honest the adjustability at that interface sketches me out. Making four different versions with four different offsets seems like it would be the way to go.

theres a chip in the center. it wont have full length steerer tube rather the chips will have a nub to fit into the headset similar to the way intend does it on there infinity fork. there is clamps on the stanchions, the slots just arent machined yet in the pics.

Posted: Feb 13, 2019 at 11:30 Quote
ktm87 wrote:
taquitos wrote:
ktm87 wrote:
working on some crowns that allow you to adjust the offset by +/- 10mm

these are the first prototype, next one is gonna have alot of changes. i like these but not very happy with them
Given the forces that are in line with that slot or act about one of those interfaces I would be surprised if it didn't slip eventually if you are clamping the steer tube in there. If you are putting something similar to a flip chip in I suppose it could work out, but the slight bit of play would weird me out. Anyway around you're going to lose a fair bit of stiffness. Also no pinch clamp for the sanchions? I'll be honest the adjustability at that interface sketches me out. Making four different versions with four different offsets seems like it would be the way to go.

theres a chip in the center. it wont have full length steerer tube rather the chips will have a nub to fit into the headset similar to the way intend does it on there infinity fork. there is clamps on the stanchions, the slots just arent machined yet in the pics.
Hmm I still think stiffness will be low compared to a standard crown. Especially if you have a through bolt from one chip to the other like the intend. If you were to bolt the chip straight to the crown with four bolts it would be more rigid.

Posted: Feb 13, 2019 at 11:42 Quote
taquitos wrote:
ktm87 wrote:
taquitos wrote:

Given the forces that are in line with that slot or act about one of those interfaces I would be surprised if it didn't slip eventually if you are clamping the steer tube in there. If you are putting something similar to a flip chip in I suppose it could work out, but the slight bit of play would weird me out. Anyway around you're going to lose a fair bit of stiffness. Also no pinch clamp for the sanchions? I'll be honest the adjustability at that interface sketches me out. Making four different versions with four different offsets seems like it would be the way to go.

theres a chip in the center. it wont have full length steerer tube rather the chips will have a nub to fit into the headset similar to the way intend does it on there infinity fork. there is clamps on the stanchions, the slots just arent machined yet in the pics.
Hmm I still think stiffness will be low compared to a standard crown. Especially if you have a through bolt from one chip to the other like the intend. If you were to bolt the chip straight to the crown with four bolts it would be more rigid.

i agree with you, this is just the first prototype and i already have quite a bit of changes for the next set. adding bolts for the chip is on the list

Posted: Feb 13, 2019 at 13:36 Quote
ktm87 wrote:
i agree with you, this is just the first prototype and i already have quite a bit of changes for the next set. adding bolts for the chip is on the list
Make sure you put lots of work into determining proper thread engagement or these people will eat you alive haha

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