Homemade Parts!

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Homemade Parts!
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Posted: May 20, 2019 at 4:22 Quote
Jurchek wrote:
Hi! This is my highschool graduation project:


*snip*
out of interest, what was your design brief for the project, and what problem did it solve? When I was studying resistant materials in hig school (15 yrs ago...) there had to be a clear issue with existing solutions that justified the design. There appear to be a lot of stems on the market, so...

Posted: May 20, 2019 at 8:09 Quote
Grumposaur: 40 kg sound a bit low, you can stand or hang on handlebars with ease.

Keep in mind that in reality stress is also
applied/spread through the frame, fork, wheelsets etc. You are not just loading your handlebar and stem with (for example) 4000N.

Any opinions on minimum radius or chamfers on the edge of the clamping surfaces of the stem to bar? Any difference for designing for carbon or alu handle bars?

Honestly I have no idea. I have just deburred edges with a file.

Therevfryslim: Out of interest, what was your design brief for the project and what problem did it solve?

Machining and making CNC programs by myself was the point of the project, not so much the design. Design is basic and far from the porn Ktm87 posted few pages back.

Posted: May 21, 2019 at 1:31 Quote
Jurchek wrote:
Grumposaur: 40 kg sound a bit low, you can stand or hang on handlebars with ease.

Keep in mind that in reality stress is also
applied/spread through the frame, fork, wheelsets etc. You are not just loading your handlebar and stem with (for example) 4000N.

Any opinions on minimum radius or chamfers on the edge of the clamping surfaces of the stem to bar? Any difference for designing for carbon or alu handle bars?

Honestly I have no idea. I have just deburred edges with a file.

Therevfryslim: Out of interest, what was your design brief for the project and what problem did it solve?

Machining and making CNC programs by myself was the point of the project, not so much the design. Design is basic and far from the porn Ktm87 posted few pages back.
Say you have a 100 kg rider, lands a bit nose heavy 50% of his weight on the front. That is already 50 kg dead weight, but for sure the deceleration will be multiple g's. The load caused by the rider are applied on handlebars and pedal/cranks, the reaction forces are at the wheel contact points. (Or actually more the loads the rider is experiencing as a reaction due to the ground stopping the vertical motion of the bike and him, are transferred to the cranks and bars to the rider)

Posted: May 21, 2019 at 7:35 Quote
Grumposaur wrote:
Say you have a 100 kg rider, lands a bit nose heavy 50% of his weight on the front. That is already 50 kg dead weight, but for sure the deceleration will be multiple g's.

True, but keep in mind a rider's arms are only so strong; the rider will collapse at a certain point and limit the maximum load.

Easton and Enve (and others, probably) have posted videos of handlebar testing procedures. Rather than trying to invent a test procedure without any experimental data, just copy what the veterans have learned and get a twenty year head start on your test design!

Posted: May 21, 2019 at 8:31 Quote
highsider, great video.

Another (and I'm sure there are others):

Posted: May 21, 2019 at 8:43 Quote
R-M-R wrote:
Grumposaur wrote:
Say you have a 100 kg rider, lands a bit nose heavy 50% of his weight on the front. That is already 50 kg dead weight, but for sure the deceleration will be multiple g's.

True, but keep in mind a rider's arms are only so strong; the rider will collapse at a certain point and limit the maximum load.

Easton and Enve (and others, probably) have posted videos of handlebar testing procedures. Rather than trying to invent a test procedure without any experimental data, just copy what the veterans have learned and get a twenty year head start on your test design!
Agree, but if static load can already be 50kg, testing should be higher than 40kg/400N.

In the video from highsider it is a cycle of:

1200N push, 250N pull, offset impact
450N push, 250 N pull, climbing
700N push, 250Npull , XC
400N push, 500N pull, hard climbing
1150N push, 450N pull, DH
1700N push 900N pull, jump impact.

So in comparison I would say 400N is on the lower side.

Posted: May 21, 2019 at 8:49 Quote
That ENVE video is also nice, but I prefer the way of testing from that syntace video. Once you got that machine set up you can do many test until failure. The ENVY guys have a labor intensive test and after 150 drops called it a day.

Posted: May 21, 2019 at 8:55 Quote
Grumposaur wrote:
That ENVE video is also nice, but I prefer the way of testing from that syntace video. Once you got that machine set up you can do many test until failure. The ENVY guys have a labor intensive test and after 150 drops called it a day.

Agree, but the Enve test may be easier for a high school student to incorporate into his design project!

Posted: May 21, 2019 at 10:30 Quote
R-M-R wrote:
Grumposaur wrote:
That ENVE video is also nice, but I prefer the way of testing from that syntace video. Once you got that machine set up you can do many test until failure. The ENVY guys have a labor intensive test and after 150 drops called it a day.

Agree, but the Enve test may be easier for a high school student to incorporate into his design project!

Making a similar set-up is easier indeed. But you would still need to do some calculations, and have to know the springconstant (or measure it) of the bottom bumper to related the height, together with the handlebar weights to a the load the bar is experiencing.

Anyway those loads of syntace are very interesting Smile

This one also has some good values in there:

Posted: May 21, 2019 at 10:38 Quote
Grumposaur wrote:
Making a similar set-up is easier indeed. But you would still need to do some calculations, and have to know the springconstant (or measure it) of the bottom bumper to related the height, together with the handlebar weights to a the load the bar is experiencing.

Again, I agree, but for a high school project, I would be satisfied if the student simply calculated the energy from the ENVE (or similar) test and used that as an input.

Posted: May 21, 2019 at 15:16 Quote
I agree and I am not trying to downtalk Jurchek's design or project. It was just the trigger to think about design a bit more and the associated loads; currently I have some time off to thing about some designing myself again. I became more a big structural steel guy and thinking of going back to more refined design work.

Posted: May 21, 2019 at 16:03 Quote
Grumposaur wrote:
I agree and I am not trying to downtalk Jurchek's design or project. It was just the trigger to think about design a bit more and the associated loads; currently I have some time off to thing about some designing myself again. I became more a big structural steel guy and thinking of going back to more refined design work.

That's reasonable.

Speaking of future projects and uncertain stresses, maybe a good project would be to create a library of stress data. Recreation riders, pro riders, heavy riders, light riders, male, female ... Strain gauges are cheap and there must exist some tiny receiver that could receive the signals and transmit it to a phone.

Posted: May 21, 2019 at 16:09 Quote
I have a piece of plexiglass about 1 foot by 1 1/2 feet and the tools to cut it, and wanted some ideas of what I could use it for.

I already have a chainguide on my bike so even though that would be one of the easiest projects to do, I'm not about to throw away my $150 one for a homemade part (even though it would be a cool conversation starter). I have a full suspension trail bike as well as a fully rigid gravel bike if you can think of anything I can make for them.

I've never made anything custom for any of my bikes so I thought I'd start small with a non-essential piece (I don't want to start off making a part that could end my ride if it fails)

Posted: May 26, 2019 at 12:23 Quote
Hello, today i made stress simulation with 500 Nforce (1000N combined). In real life I must say that after a few rides the stem does its job.

EDIT: I messed up simulation. Here are results for load with about 14000N on every side



 
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