How many engineering students does it take to change a cassette?
 

Just one, but expect him to take a looooooong time..

I had just gotten out of a final exam this morning and I thought to myself this would be a good time to install my new cassette. I had all the necessary tools for the job, so I got to it. Unfortunately, the last time I installed my cassette, I tightened it probably a bit too much so I was struggling to get the darn thing off. During this process, I ended up breaking my chain whip..it took me a a few more minutes to jimmy the thing back together with a chain tool and I finally got the cassette off.

"Hard part's over with" I thought to myself...but this was just the beginning. I slid the old cassette off and put the new one on, tightened everything and put it back on the bike. I immediately noticed some weird shifting going on; it wouldn't shift to the smallest cog. Strange...very strange I thought. I had never adjusted the limit screws before, so this was a first for me. After a few more minutes of looking up which one was the high and low limit screws, and messing with the cable tension a bit, I finally got the bike to shift fine. PHEW. That's done with, or so I thought...

As I was putting away my tools and the old cassette, I noticed that the old cassette was missing a spacer behind the largest cog...uh-oh...a light bulb went off in my head and I took off the cassette I had just installed and sure enough, there was an extra spacer in the back....crap...So I removed that spacer, installed the cassette AGAIN, and then had to mess with the limit screws once more to undo what I just did...

All in all, it took me about well over an hour just to swap out one cassette, but I learned a ton and honestly, although it was frustrating that it took so long, I still loved every minute of it.

haha, that sounds almost exactly like my first time changing a cassette, except I didn't have a chain whip and I tried to rig up my own with an old chain. I missed the spacer and went through exactly the same routine. They seem to naturally tighten on their own.

What kind of cassette did you replace and what did you replace with?

Congratulations, you have just learned the difference between an engineer and a mechanic!

:thumb:

Erm...I'm a machinist and I did that one time too.

So don't feel bad.

LOL! So true.

The good news is it will probably be so long till you replace the cassette again you'll have to relearn some of the same things. :D

This is what bike shops are for. You said you enjoyed every minute of it, though, so maybe not.

replaced a 11-23 with a 12-25. I just wanted that extra gear for some climbing.

I just did my first cassette swap ever last night and get this: I didn’t even know it would require special tools! I thought you could just take off the wheel and the cassette would slide ride off. (Believe it or not, this IS the case with the rear cog on my motorcycle.) So I went to the Park Tools site and the LBS four blocks away had what I needed. They were still open for another 20 minutes.

PS – chain whip is THE coolest tool name in history. I was happy to buy one just for that.

Also – now you guys have me paranoid that I missed a spacer! Gears ran fine this morning though…

Cheers to having our first cassette jobs behind us.

You know, this is soooo true about mechanics in general, certainly in my case.

I collect spores, molds and fungus in my refrigerator and I have never done this to a cassette.

I have re-cabled my bike though, and forgot to wrap the brake housing under the tape. Two layers of tape.

*applause*

.

FTFY. Proper tightening of a lockring is a minimum of 40nm. Basically you want to tighten it, till it stutters a bit. A tight lockring is much better than a loose lockring.

Uhm, are you sure that "extra spacer" wasn't the spacer that goes behind a 10 speed cassette, on an 8,9,10 speed wheel.

That's supposed to be there, and the reason thing weren't shifting right could be that you didn't tghten the lockring down as far it's supposed to go, not that there was an extra spacer.

If you actually had an extra spacer on, it's unlikely you could have even gotten the lockring down far enough to start threading it.

So the jury is still out on whether one engineer is sufficent to change a cassette.

Sounds about like my experience anytime I do something new on the bike (or home, for that matter). After a few times though you learn some of the gotchas and become more efficient.

Engineering student roster:
1. Requirements Analysis - need to develop fixture and other tooling requirements
2. Mechanical Design - design necessary fixtures and tooling
3. Mechanical Analysis - perform necessary finite element analyses to ensure structural integrity
4. Test Engineering - develop acceptance test specifications and procedures
5. Test Equipment Engineering - develop host HW and SW for the acceptance test
6. Manufacturing Engineering
7. Engineering Management

Or, 1 mechanic

You did say this was a production operation

Let me know what company you end up working for...

Jiggle the largest cog of the cassette after installing it to make sure it's tight lol, don't just assume

Wisdom cannot be taught, it must be experienced.

First time designing a race car part and revelling in the glory that is SolidWorks. No right angles on the part - those are stress raisers. Maximum sized radii on all corners. Everything profiled and smooth. The final drawing is a work of art.

Delivered to the machinist for CNC, and he comes back "I can't make this".

Huh? It's CNC and MasterCAM converts SolidWorks models directly. What's the issue?

Well, for instance, this radius that you called out at .471 - it's a 3-axis machine. The only way to cut that radius is to rough it out and then come back with a round nose cutter and take like a thousand paths which will tie up the machine for hours. Or you can change it to a .25 radius, we'll use a 1/4 round nose, and cut it in one pass. Etc etc. Tons of other examples.

Revolutionized how I thought about part design - it's not just what it does that drives the design, but also how you make the damn thing.

DG

This is why I asked the OP what kind of cassettes he is working with.

OP: I was looking for the brand and speeds, not the size.

what exam did you just finish?

Shimano 105, 10 speed. I'm 100% certain that I had the extra spacer on because when I initially tried to screw on the lockring, it didn't go on smoothly, but still kind of went on. Also, before installing the cassette, I looked over the Shimano tech-docs to make sure my new cassette had all the necessary spacers.

and dleccord, I had just finished an exam in strength of materials.

don't feel bad... I have [somehow] had multiple shops and multiple mechanics do the SAME thing on my mavics. Sad but true... and I always pick the wheel up and shake the cassette... and then they look at me with sudden nervousness and take the wheel back and add the necessary spacer.