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Mechanical Engineering Design student - help me on my mountain bike shock project!

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Mechanical Engineering Design student - help me on my mountain bike shock project!

Old 04-13-09, 11:08 AM
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TTM
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Mechanical Engineering Design student - help me on my mountain bike shock project!

Hi guys/girls,
For my mechanical engineering junior design project we were assigned to create a mountain bike shock. Our team chose to design a single arm coilover system (similar to the cannondale lefty, but much more simple.) The design has essentially been completed, all technical analysis completed, the details of the shock and damper finished.

I am asking you guys to help us decide which paint scheme to go with. It would add a good deal of credibility to our final report to get your input.


1. White n teal


2. Black n chrome


3. Blue green yellow


4. Orange and Black


5. Tan n White


6. Teal n Copper


If you could just rate 1-6 on a scale of one to ten, one being very ugly, 10 being very attractive.
This is what we are looking for:

1. 4
2. 6
3. 1
4. 9
5. 10
6. 2
If you want to comment on how you feel about particular color schemes or our design feel free.
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Old 04-13-09, 11:28 AM
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Blue green yellow FTW
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Old 04-13-09, 12:06 PM
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Is there any reinforcement between the bottom of the coil and the top of the coil? From what you have pictured, it seems like the piston is all that's there, and that it would bend/break pretty easily. Needs a BEEFY slider to maintain rigidity IMO.
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Old 04-13-09, 12:58 PM
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Originally Posted by frankenmike View Post
Is there any reinforcement between the bottom of the coil and the top of the coil? From what you have pictured, it seems like the piston is all that's there, and that it would bend/break pretty easily. Needs a BEEFY slider to maintain rigidity IMO.
I agree with this poster.

But if you don't care and just want to hear a color scheme, I'd say Black & Chrome.
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Old 04-13-09, 12:59 PM
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1. 9
4. 8

others i dislike.
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Old 04-13-09, 01:05 PM
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4. 8
6. 9
others: 5
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Old 04-13-09, 01:15 PM
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5 4 1 and 2 aren't bad, 6 and 3 really don't do much for me.

Is a bit of an silly question in some ways though, I mean just look at the range in the bike pic thread. Green seems to be rather in fashion on frames atm though, and white seems to be liked by lots for forks, bash guards etc.

A poll of "pick your fav main colour for a bike fork" would have possibly been better, then once there is a clearish winner do a set of pics with different accents for people to choose from.
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Old 04-13-09, 01:30 PM
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You should really think about anodizing instead of paint. Looks much cooler on the small pieces.
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Old 04-13-09, 02:04 PM
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I really think 'bent-and-no-longer-functioning' will be less conspicuous in black.
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Old 04-13-09, 02:14 PM
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All Flaming aside...
I would go with a Burnt Orange and Black.
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Old 04-13-09, 02:36 PM
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Originally Posted by frankenmike View Post
Is there any reinforcement between the bottom of the coil and the top of the coil? From what you have pictured, it seems like the piston is all that's there, and that it would bend/break pretty easily. Needs a BEEFY slider to maintain rigidity IMO.
+1

Rear coil over shock units only handle compression and tension loads (the rest are handled by the suspension linkages). However, when that design is transposed into a front fork unit, it will have to handle bending and torsional forces as well... plus being a "lefty" (in your case a "righty" ) also something strong enough to keep your axle from swiveling when the handlebar isn't being steered.

Hollow 20mm thru axles are currently being employed in two legged forks, so an axle being supported by one leg from only one side would have to be larger still I would imagine.


Otherwise, if it's a rendering exercise, 5 looks cool to me, and then 2 is my second pick out of your choice of options.


All the best to your project.

.
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Old 04-13-09, 03:10 PM
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Orange and Black or Black and Chrome


I would stay away from 3 and 4 color designs because it makes it much harder to match with things.... a little bit of color can be good, but when you've got that another color working against it can detract from things.


Unless, of course, you want a rainbow bike.
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Old 04-13-09, 06:12 PM
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Black and brushed aluminum would be my choice but that is not a choice you have so black and orange.
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Old 04-13-09, 06:29 PM
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YETI teal and white, of course.
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Old 04-13-09, 08:52 PM
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I do see where you guys are coming from, in these pictures the piston rod is very flimsy looking - this has since been changed (we are just looking for paint scheme input ATM.) We have crunched the numbers and the rod has enough inertia and tensile strength to handle a quick head on collision.

There are a whole variety of problems when symmetry is taken out of the equation on these righty/lefty systems. Our team didn't want to *****foot into this assignment so hopefully we get brownie points for picking an inherently difficult design.
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Old 04-13-09, 09:32 PM
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What are your school colors? Paint the shock in those colors.
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Old 04-16-09, 07:30 AM
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Originally Posted by laura* View Post
What are your school colors? Paint the shock in those colors.
+1

the teacher/principal would love it and be biased...
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Old 04-17-09, 11:56 PM
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so with the spring and damper in a line, we're talking ux = bx dot + kx ? Find zeta/ omega natural and omega damped. HA
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Old 04-18-09, 12:28 AM
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black/chrome.

and not sure how you've changed the design since, but what you've got posted here in practice looks to be in line to become very non-functional very quickly with real world use.

if that is anything resembling "to scale" it looks as if it'll be flexy as hell besides.
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Old 04-18-09, 08:52 AM
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Lefty DH is like communism really.

70% less moustache however.
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Old 04-24-09, 12:49 PM
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You guys provided some valuable input. We beefed up the titanium piston tube. It CAN withstand a 20 mph head on collision with lockout enabled. 5 inches total travel. Its on the heavy side around 7 or 8 lbs.
This is the final design.

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Old 04-24-09, 12:51 PM
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Originally Posted by 4zn_balla View Post
so with the spring and damper in a line, we're talking ux = bx dot + kx ? Find zeta/ omega natural and omega damped. HA
We aimed for critical damping in a washboard situation. (using the standard second order spring-mass-damper system equation)
gobak2skool
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Old 04-24-09, 02:00 PM
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Here's a diagram of Cannondale's Lefty Jake fork:



Notice the... beefy inner tube. It's a major structural component of the system fork, and also encloses the compression and rebound damper pistons, which are there only for damping and are not structural. In your case, you seem to be relying on the shock pistons for structural support, and that seems dodgy.
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