Homemade Parts!

PB Forum :: Mechanics' Lounge
Homemade Parts!
Author Message
flag Will1848
Posted: Feb 2, 2019 at 11:18 Quote
FYI, throw the seals in the freezer beforehand and they go in much easier. I’m able to do my Pike with just my fingers.
flag teedubya
Posted: Feb 2, 2019 at 12:29 Quote
Also works a treat on bearings, headset cups etc.
flag SuperstarComponents
Posted: Feb 10, 2019 at 8:33 Quote
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
flag Davec85
Posted: Feb 10, 2019 at 8:50 Quote
Will1848 wrote:
FYI, throw the seals in the freezer beforehand and they go in much easier. I’m able to do my Pike with just my fingers.

I will be doing this next time, never thought of doing that. Had a nightmare trying to get them in last time.
flag ktm87
O+
Posted: Feb 10, 2019 at 11:23 Quote
stem im working on. its a work in progress
photo
photo
flag RunsWithScissors
Posted: Feb 10, 2019 at 12:01 Quote
ktm87 wrote:
stem im working on. its a work in progress
photo
photo


Beautiful workmanship. I like it. Thanks for posting!
flag ktm87
O+
Posted: Feb 10, 2019 at 12:08 Quote
thanks appreciate it! making a small batch for some friends. I wanna make some in titanium too. Friends are trying to convince me to sell them but i don't know. I feel like the market is already so full of stems and this isn't anything special.
flag RunsWithScissors
Posted: Feb 10, 2019 at 13:15 Quote
ktm87 wrote:
thanks appreciate it! making a small batch for some friends. I wanna make some in titanium too. Friends are trying to convince me to sell them but i don't know. I feel like the market is already so full of stems and this isn't anything special.

I think you've got the right idea. It can be the best stem ever, but still there's a shit ton of stems out there already that work. Without a full product line it's real hard to make money on components...
flag inked-up-metalhead
Posted: Feb 10, 2019 at 13:25 Quote
Stems should fall into two camps if you ask me. Cheap, strong and a bit overweight (truvative hussefelt style) or blingy as shit. Other than matching your bars or colour scheme, what can you actually ask from a stem other than not breaking? It's not a subjective part like most stuff on a mtb, there's no real benefits of one over another providing the geometry is the same, it's purely aesthetics and or wanting bling. Ive had hopes, race faces, a spank, few other higher end stems along with a hussefelt (which is still going strong at 12 years old, its the only surviving part of my original mtb) and my current Titus 45 quid special. I've never noticed any difference (ignoring length) between them.
flag latheboy
O+
Posted: Feb 10, 2019 at 20:57 Quote
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.
flag Mr-Magura
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
flag latheboy
O+
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 ?
flag latheboy
O+
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.
flag secondtimeuser
O+
Posted: Feb 11, 2019 at 14:31 Quote
I feel your pain. Non-standard bolt lengths are a blight.
flag Mr-Magura
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

 


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