Messages

46

The Bike Shop / Re: Pre-Order your Barcodes

« on: February 24, 2015, 06:04:48 AM »

I don't see all the fuss about mid vs. spanish.  If mid gets me a little more brake clearance, cool, otherwise, I can't seem to find any fucks to give either way.

47

The Lounge / Re: Frame Features /Strength

« on: February 24, 2015, 06:02:50 AM »

I've been thinking about this, and intuitively, I think wishbones should be more rigid up and down (I.e., about and axis through the bb), and side to side (axis normal to the ground), but less rigid in twisting.

I could probably work out how to prove it, but my structures fu is not strong.

If you can prove that then you should move on to prove that up is down and black is white. One big one will always beat two small ones...


G.

First and foremost, It's been a long time since I've done any work like this, so I would certainly defer to your expertise.

However, what I was thinking is that trying to twist the rear wheel, (like imagine putting a bar through the dropouts and standing on one side), the lower wishbone would be in pure torsion, and there would be a bending moment at the top wishbone, with a moment arm length of something like standover height - BB rise.

On a standard rear triangle, the single bending moment would be replaced by two bending moments, one at each seat stay, and the moment arm would be marginally longer (the hypotenuse of a triangle with vertices at the center of the axle, the dropout and the center of each seat stay).  Additionally you would replace the torsion about the lower wishbone with two bending moments, but I can't remember if that's a good thing or not, especially considering that lower wishbones are rarely circular.

So that’s where I stopped, because even if this line of though was accurate (I’m not sure it is), I’m pretty sure that if you held mass constant, you could plug in all the material properties and over some range of section dimensions, one would be better than the other, and over another range of section dimensions, the other might be better, and there is absolutely no guarantee that you could make a tire fit on any of the optimized solutions.

And ultimately, that’s not really a loading I think we care a whole lot about.  I don’t think a little twisting on a peg stall, or landing with some sort of yaw is going to be noticeable.  Obviously, that’s something I think I would be willing to compromise to make the structure stiffer when you apply a downward force to the bottom bracket.
One of these days I’ll dig my books out and prove myself wrong, in the meantime, hopefully I’m not sounding like too much of a muppet.

48

The Lounge / Re: Frame Features /Strength

« on: February 20, 2015, 07:16:34 AM »

Just bondo over the bolt hole.  No one would ever know. 

49

The Bike Shop / Re: Yakob/Merged article on tyre size

« on: February 20, 2015, 07:14:49 AM »

I've asked this in a few places, and never really got a credible answer, but where have all the folding/k-lyte/p-lyte tires gone?

What's a rotating weight whore got to do to get some love?

50

The Bike Shop / Re: Yakob/Merged article on tyre size

« on: February 20, 2015, 07:12:27 AM »

i noticed on insta this morning that fit has restocked all their big fat coloured street tyres in 2.3 and 2.4, but are also now going to be offering them in 2.1

is the market switching back to thinner tyres again?

Mother of god.  I can only hope.  That is my tire size of choice but it is so hard finding anything worth a damn.  Aitken 2.10" is about all that is out there (IMO) that is worth a shit.

Maxxis Grifter/Rizer

51

The Bike Shop / Re: Pedal design devolving?

« on: February 20, 2015, 07:11:16 AM »

God I love tacos.

Really though, the option of treating pedals as a wear item is long overdue.  For whatever reason, I've always been really hard on pedals, and I've bent a lot of spindles, and I've never had a lot of luck working on pedals as I can never get the lock nut tight enough without overtightening the cone.  I also hate the way bent spindles feel, so to get pedals that (1) are cheap to replace and (2) come with much stronger spindles is fucking tits.

I don't see the really nice, sealed aluminum pedals ever going away, but to have the option of buying Twisted PCs 5 pairs at a time and treating them like grips is great.  I literally just change them out because I've used them for a few months and they feel a little warn down or rattle a little too much.

The kids in my hood love it too, cause they are all running around on barely used Twisted PCs.

I really like the idea of bushing pedals also.  Anything that reduces part count is a good thing in my eyes, and the ease of maintence is absolutely ideal.  However, I haven't been impressed with any of the bushing pedals so far.  I own a pair of BPEs, and I manager to get them to not rattle, but the bodies are just too thick for my taste, and I don't like that if I crash riding trails, I get a ton of dirt into the bushings. I'm also kind of getting the impression Animal gave up on them.  The Kinks look too much like the PC Rubens, and I really hate the way those feel.  I've got high hopes for the Dugan pedals.

52

The Lounge / Re: Frame Features /Strength

« on: February 18, 2015, 07:15:38 PM »

One of my friends had a Barcode. I distinctly remember dropping into a quarter pipe on it and being surprised by how much stiffer than my non-wishbone frame it was.

That was definitely my impression the first time I pumped up a transition on my Barcode.

It was actually just a little scary at first.

53

The Lounge / Re: Frame Features /Strength

« on: February 18, 2015, 06:04:00 PM »

I've been thinking about this, and intuitively, I think wishbones should be more rigid up and down (I.e., about and axis through the bb), and side to side (axis normal to the ground), but less rigid in twisting.

I could probably work out how to prove it, but my structures fu is not strong. 

54

The Bike Shop / Re: Yakob/Merged article on tyre size

« on: February 17, 2015, 09:24:12 AM »

Rubber is just really flakey and inconsistant.

I worked as a mechanic at one of these high performance indoor karting centers while I was in college, and we went through a lot of tires.  We also had a timing system that was reporting times to customers to the thousandth of a second, so we got tons of complaints about such and such kart is a dog, or such and such kart is really fast or whatever.

So one of the things I would do to to equalize karts was mess around with the rear tire diameters.  Tires came in boxes of 12, and within a box there would be variation of up to an inch in inflated diameter (it was around 31-32 inches).  I actually plotted four or five boxes at one point (as a bored engineering student, I tended to do shit like that) and it took two deviations to capture 75% of the tires.

I wrote that whole expirence off to buying cheap, rental kart tires, but once I graduated and got my current job, one of the first things I worked on was an inflatable EPDM seal for a 36 inch steam valve.  This bitch was crazy.  It was inspected and measured at numerous steps, held to insane tolerances, had a rejection rate that a non-government customer would never accept, I mean this seal was visually inspected three times by three different organizations before it was X-rayed.  It would have been cheaper to press $100 bills into an O-ring to seal this valve.

One of the qualification tests I had to do was to inflate the unrestrained seal to some pressure lower than the working pressure and measure the inflated height.  Inspite of the inspections and tolerances and rejections, two deviations to capture 75% of the seals.  My sample size was a lot smaller (12 seals), but still, tons of variation.

Based on those expirences, I think it's difficult, even within rubber products manufactured from the same lot of materials to the same specifications cured on the same day in the same mold, to predict inflated dimensions of rubber things with the sort of accuracy we're used to.

Granted, there are some significant differences between bike tires, go-kart tires, and inflatable steam seals, e.g., the rubber compounds, thickness and so on.  Additionally, just pulling numbers out of my ass, I would guess that if a mean bike tire diameter is 21 inches, two deviations would get you 20.875-20.125, which is likely not significant.

I'm not sure I have a relevent point here, but when that article came out, this variation in inflated diameters was what came to mind.  It's not something you can fix, or even predict, it's just part of working with inflated rubber.

55

The Lounge / Re: i might just be getting old...but two vids with blow/mdma on TCU in 1 week?

« on: February 16, 2015, 08:49:54 PM »

Man, that video is beyond horrible.

Its cool that they are having fun or whatever, but that shit almost gave me a seizure.

56

The Bike Shop / Re: Quick question for machinists

« on: February 16, 2015, 09:59:45 AM »

I'll preface this by clarifying that I'm not a machinist, but they do occasionally let me put down specs long enough to design machined parts.  I also work in an industry where we often don't give a fuck about money.

But for a critical pinned joint like this, where even small amounts of play would not be acceptable, we would drill the hole intentionally undersize, and finish hone it until the actual bolt being used just fits.  In face we sometime specify the allowable force to insert the bolt to make sure someone doesn't get crazy with a hammer because they are ready to go home.

Doing so allows us to get the fit we want regardless of the tolerance stack-up.

57

The Lounge / Re: hella new school geo makes our tricks look dumb.

« on: February 12, 2015, 03:28:55 PM »

The thing with bars is that wide, tall bars just feel better.  I cut some Benny bars too narrow awhile back, and they were worthless. I just put them on my kids bike.

Don't get me wrong, I like my bike to be aesthetically pleasing, I want to ride my bike more when it looks good, but I'm a function first dude, generally speaking.

58

The Lounge / Re: hella new school geo makes our tricks look dumb.

« on: February 11, 2015, 06:15:13 PM »

u run 2 in da back 1 in da front?

gangster

Ran. Past tense. I'm a strictly 2 or 0 peg dude these days.

59

The Lounge / Re: hella new school geo makes our tricks look dumb.

« on: February 11, 2015, 03:24:13 PM »

far as I'm concerned, if you're not riding 4 pegs, front brakes and a gyro, YOU'RE CHEATING!!!

cheating yourself out of a whole lot of fun.

if you didn't ride in the 80's, you're opinion is not valid.

If you did ride in the 80's but quit, post pics of your wife tecnic1

I ran three pegs in the 80s. I like to say it was so I could feeble both ways, but the truth is it was so I could still give people rides.

60

The Bike Shop / Re: definitive freecoaster thread

« on: February 10, 2015, 07:43:19 AM »

Cult v1 and v2

I see your problem.  Too much cat hair.  I try to go for a light sprinkle of cat hair, you seem to have caked it on.

Also, try to find Calico hair.  Tabby will work in a pinch, but calico is much smoother.