Tifo,

You work for Airborne right? I love their bikes. I hope to get one someday when my Bontrager needs replacing. Before I joined the Air Force I was in the bike buisiness for about 3 1/2 years. I sure do miss it sometimes. What do you do exactly if you don't mind me asking..

 

[quote]Originally posted by Manning:
<strong>Ribs,

Didn't you have a Celica All Trac? What happened to that?</strong><hr></blockquote>

I sold it 2 weeks ago, settled some debt that I had, and used the money left over to buy an '88 rx-7.

Ironically, the celica came stock with a strut brace that wasn't straight across the engine bay but braced to the firewall too.

-rich

 

Did you sell it for any reason other than to get some cash? Like, is there some indiosyncratic flaw in that car that makes it a ticking time-bomb? I'd love to get one of them sometime, or a Galant VR4, you know, one of the funky AWD limited number cars from the late 80's early 90's.

And you know, it is kind of funny that a lot of cars seem to come with/came with an actual triangulated strut brace. Look in the back of an MR Spyder for example. I can't really even think of where your would bolt up extra members easily without reinforcing the sheet metal on our cars. And would it be better to make it like an X, or like a triangle.

 

Yo Tifo,

I thought of another question that you kind of already answered (and I am absolutely not trying to be argumentative, I find this stuff very interesting).

So other than the "buzz" that seamless Ti tubing will create, is there really a point regarding use on a bicycle? I honestly cannot recall any failures on any of the Ti bikes we sold, except for one of the guys on our team whose drive side chainstay broke on a Litespeed mtn bike. Granted it was at the dropout, so in a heat affected zone, but it was also a couple years old and ridden HARD. The only other failures we ever heard about were on some of the first few bikes that were using cheap Russian titanium. I think it was because some of the cheap Russian stuff wasn't alloyed properly or something.

It kind of seems to me that this tubing will be really pricey at first, do you see a market?

How about the manufacturing question I had?

And regarding exhausts, there is a place east of me (in Chagrin Falls, OH I think) called Stainless Works that is willing to do custom tubing bends in Titanium and Inconel and such as long as you are willing to shell out the Benjamins since they will only doit in quantity. I figured this might be of interest to Turbo Tim and Danno and all.

<a href="http://www.stainlessworks.net/Bends%20&%20Tubing.htm" target="_blank">Stainless Works</a>

 

"20 to 30mm!!! Are you kidding me?! We even had a hard time getting that much deflection when we were trying to align forks on an alignment jig. That said I have watched really light Columbus tubed forks chatter over washboard. But almost and inch?"

Yup, you can get about 1.2-1.3g of decceleration and that really bends the forks back. On an alignment jig, you can bend the fork blades by hand. Now imagine leaning the bike over 30-degrees, rocking back and forth in a sprint, with a 200-lb rider generating over 300-lb•ft at the crank... heh, heh.. I've seen slow-mo videos of Davis Phinney and that Russian guy.. Abdujasparov. You can definitely see that fork bend laterally several degrees. That's why track forks have round tubes.

"Think about were most forks fail (I've literally seen hundreds of failed forks over the years). I think every fork I ever saw fail, both road and mountain bike, did so at or near the crown (within 2 to 3 inches of the crown race)."

Exactly! The fork is a cantilever arm. And since the load is applied at the end of the arm, the rotation is around the point where the arm attaches to a fixed point, namely the crown. The point where the arm goes from flex to no-flex is a stress riser and will be the point where it fails due to the highest torque. So the tips of the fork is where the greatest longitudinal and lateral displacement occurs due to the flexing takes place. And the crown is where failure will occur due to the torque from that flex.

Good example can be illustrated by hammering a nail halfway into a board, 2x4 or tree... Then grab the head of the nail (fork dropouts) with a pair of pliers and wiggling it sideways to simulate braking forces and weight outside the plane of the bike's frame. You'll notice that the part that moves the most is the head of nail where you're applying the force. And it pivots around the spot where the nail enters the wood. With enough flexing, the nail will eventually break near that spot. That's because the highest torque is at that location with stress-riser. If you put the nail into a non-deforming block of iron, it will break a couple millimeters outside of the block. There is also a slight difference in the break depending upon whether the nail broke due to a single overload that is greater than its ultimate strength, or whether it failed due to fatigue. But in both causes, it will occur at the point with the highest torque; at the stress riser opposite the cantilever arm from where the load is applied.

"I think a lot of the perception that straight bladed forks are stiffer is because so many where built with bigger therefore stiffer blades"

This just contradicted the earlier statement. If the fork-blades don't bend & flex under load, then there shouldn't be any difference if you build with bigger stiffer blades? But it does make a difference...

"So other than the "buzz" that seamless Ti tubing will create, is there really a point regarding use on a bicycle?"

Personally, I've used a ton of Ti parts on my bikes (weight in cash, inversely-proportional to weight-saved in Ti). I managed to bring my crit bike from 16-lbs to just under 14-lbs without sacrificing any durability (bike needed to last one season without major overhaul). Things that don't require a lot of stiffness due to triangulated geometry or being overbuilt can use Ti parts to save weight.

Things like:

- nuts, bolts and washers
- hub shells, axles, bearing adjusters and locknuts
- quick-release skewers
- bottom-bracket spindles
- pedal axles
- seat rails (with carbon-fibre shell)
- Regina had a Ti chain, didn't wear too well, but can probably get away with the link-pins in Ti.
- cassette-sprockets, 1/2 the weight of steel, more durable than Al

One thing that wasn't available at the time that I would've loved to get is a Ti track handlebar. Even in the strongest Cinelli 26.6mm sizes, the aluminium ones just can't last an entire season. I was lucky one time and found a tiny crack, or else that would've been the end as I'm sprinting for the finish at 48-49mph around a 2.5g corner with 8 guys just inches way from me...

There's an awesome photo a Russian sprinter at the '90 or '91 World Championships holding up 1/2 of his handlebar that he ripped off just as he crossed the finish line. Anyone have a photo of that?

 

[quote]Originally posted by Manning:
<strong>Did you sell it for any reason other than to get some cash? Like, is there some indiosyncratic flaw in that car that makes it a ticking time-bomb? I'd love to get one of them sometime, or a Galant VR4, you know, one of the funky AWD limited number cars from the late 80's early 90's.
</strong><hr></blockquote>

Well...the carrier bearings in the rear differential were loose as hell causing a thunk between every gear change/throttle change, and that rear diff is very very hard to find and costs lots of $$$ to rebuild. The car had such awful body flex that I could barely close the door when I had 1 side jacked up, it was way to slow for the amount of power that it had, way too heavy, and understeered too much for my liking...not to mention that the rebuilt turbo with 10,000 miles on it was spewing oil and it was going through a quart every 500 miles. It was too much stuff in one car...thats how I feel about most AWD turbo cars though.

It was a lot of fun to go down a muddy dirt road at insane amounts of speed in though...

If I was going to get an AWD car from the early 90's again, I would probably go with a mazda 323 GTX as they are the lightest of the bunch, turbocharged (more or less a turbo miata engine), and could be made blazingly fast while not feeling as heavy as other AWD cars of the vintage.

I saw this one guy who has a galant VR4 with a built motor, T70 turbo, some fuel management computer that I never heard of, and all of the bells and whistles...and it looked like a complete beater (torn up interior, faded/dented paint, stock wheels)...I think it put somewhere around 600 HP to the wheels. It had this nifty trick with the ECU...he would pull up the parking brake, and the timing would advance 60 degrees (I think) and it would build 15 pounds of boost at 3000 RPM's while standing still...that would give some insane launches from a stop.

-rich

 

Danno wrote:

[quote] This just contradicted the earlier statement. If the fork-blades don't bend & flex under load, then there shouldn't be any difference if you build with bigger stiffer blades? <hr></blockquote>

Hold on, in what statement did I say that forks don't flex and bend under load. What I said was that:

1) Curved versus straight blades make little to no difference as far as rider comfort is concerned because the MOI is at or near the crown, not near the curve in the blades.

2) I find it hard to believe that a (modern) fork is bending for and aft and side to side as much as 1 inch especially since side to side loads will be absorbed to some degree deflection in the wheel and tire.

1 inch of deflection will visually be quite obvious. Even when observing some of my friends and co-workers pulling stoppies and nose wheels on both road and mtn bikes, I cannot recall a single occasion where the fork flexed that much. Hell, even when I did race, or while watching the various crits around Atlanta or Athens I don't recall observing a wet noodle fork as you describe. And I'm 6'5" and weigh over 200lbs (64cm frame).

Edit These friends I mentioned, BTW, are a nationally ranked professional Observed Trialser, a national level NORBA professional down hiller (and USCF Cat3 road racer), a national level NORBA womens pro cross country racer, a regional NORBA junior cross-country champion and a regional NORBA junior down hiller. We weren't hurting for good cyclists at our shop.

My point about the alignment jig is that yes, you can bend a fork on a jig by hand. However even with the fork rigidly mounted in a basically immovable jig, it was hard to get a fork to bend as much as an inch. There even used to be a "tool" listed in the United Tools catalog that was described as a sturdy piece of white ash (basically a baseball bat) to be used to help pry a fork or frame back into place because that much persuasion is needed to help bend the fork blades.

Danno wrote:

[quote] Personally, I've used a ton of Ti parts on my bikes (weight in cash, inversely-proportional to weight-saved in Ti). I managed to bring my crit bike from 16-lbs to just under 14-lbs without sacrificing any durability (bike needed to last one season without major overhaul). Things that don't require a lot of stiffness due to triangulated geometry or being overbuilt can use Ti parts to save weight <hr></blockquote>

Yeah, I get that. In fact I have a bunch of Ti bits and pieces on 3 out of 5 of my current bicycles. My question was, is there any real benefit to going to the expence of creating seamless tubes for building frames when seamed 6/4 has been such a superior material all these years, and has become somewhat more affordable at that. What I was getting at was will this new seamless tubing be cost effective for use in commercially available frames, or will it be limited to pro level or national team level bikes (at least for a while).

And I am not trying to be rude, but are you saying you weigh 200lbs and ride a 54cm frame? Jeez Luise, are you build like a fire plug ?

 

"And I am not trying to be rude, but are you saying you weigh 200lbs and ride a 54cm frame? Jeez Luise, are you build like a fire plug ? "

Well, I was only 160lbs when I was racing. Eating 10,000 calories/day kinda piles on the pounds quickly when you're not racing! Even with the lower weight back then, I still looked like one of those East German genetic experiments with 25" thighs! I've shredded my share of handlebars and frames. Ripped apart one of those Peugeot Vitus-wannabes, Concorde high-tech construction my a**!!!