Mountain Biking - can you explain the 1.5 headtube?

I'm confused on this whole theory. I have searched and can't find anything that answers my question. So here we go

Ok in my head this is what I think. A smaller diameter tube is a more compact sound structure. If you have a larger tube you have more surface area and thus allows the walls of the larger headtube to be ovalized/dented easier. If it is smaller it will hold up to internal pressure better than a larger tube, granted a larger tube will hold up to external pressure from bending better, but we are talking about internal from the steerer tube.

Kinda like a piston, a smaller piston holds more pressure than a larger one. (that's the best example I can come up with)

I mean I'm not saying a 1.5 headtube is bad or anything like that, all I mean is that I want to understand how it all works. So I can learn!!

Or is the 1.5 headtube not that much stronger ....but it allows fork builder to just put a larger steerer tube on their forks to somehow make forks a bit stiffer?

Thanks in advance guys!!

:beer:

SLC, I thought it was done (larger dia.) to allow more surface area for welds and gussets at the head tube/top tube/down tube interface. The bigger the area will strengthen the whole connection due to the added forces of the longer travel fork (longer lever arm). Not so much to reduce ovalization of the headtube itself.

I could be wrong, not the first time, not the last!

L8R

1.5 was introduced by manitou in order to be able to produce 6" SC forks. Apparently Marzocchi came to the rescue and produced a perfectly sound 6" SC fork with a traditional 1,1/8" diameter....so much for 1.5"....

Originally posted by a2psyklnut
SLC, I thought it was done (larger dia.) to allow more surface area for welds and gussets at the head tube/top tube/down tube interface. The bigger the area will strengthen the whole connection due to the added forces of the longer travel fork (longer lever arm). Not so much to reduce ovalization of the headtube itself.

I could be wrong, not the first time, not the last!

L8R

A2's statement is perfectly sound but i think that with rings and hourglass shapes or simply with thicker headtubes the same result may be obtainable with more efficiency and more importantly without having to switch to a specialized diameter headtube.

From the research I've done so far all I can see is that a 1.5 steerer tube will allow manufactures to build a supposedly stuffer fork, but all this stuff that I have heard about the headtube being stronger/less ovalizing(if that's a word) is a theory, I haven't seen or heard any facts about it.

But yes A2 that would make sense about there being more area to weld to. But I woud imagine that it wouldn't be enough of a difference to warrant changing the industry standard or 1.125 or 1 and 1/8th... how ever you measure it. Again just my thoughts! I hope I can get some kind of facts from someone.

When this whole debate started, I remember the engineers at Marzocchi thought it was a bunch of malarkey, and produced the Z150 to quell the doubters.

I'll stick with my 1-1/8 until there is conclusive evidence to change, or, I'm forced to change by the entire industry adopting this. (Doubt that's gonna happen).

L8R

The facts lie in CORPORATE FINANCE, allow me as a phd student (wiseguy and showoff :D:D:D:D) to say that manitou paid some cash or more probably offered cheaper OEM 1.5 forks to RM/Scott/Orange to accept 1.5 in their frame designs. Other than that...its just business, money make the world go round and its sad but its true. Nobody up there cares about riding/computing/etc etc more than the profitability of a product. They only care about a customer as long as their care is able to produce profits. If the profits are made then no further customer care is needed.

Cheers.

HHMMMM here's a thought... if they want to make the steerer and crown stiffer why not make it all one piece, kinda like RS did with the carbon steerer/crown on the sid (NOT saying it's a stiff fork), just that maybe if they formed the alum steerer and crown together it'd be stiffer?( should I get a patent on that idea) hahaha

In early 90s tube manufacturers came up with internal designs on tubes. Splines on the inside of tubes that made the tubing stiffer, stronger and more fatigue resistant. Titanium tubes that were way stiffer than normal tapered/butted tubes appeared, however the concept disappeared with no reason. Putting Splines or internal infrastructure inside a tube is a HUGE solution imho that could really change the scenery in Frames/Forks and other tubed constructions. That's from my humble aerospace background.

Anyhow the concept is similar with the idea of internal gusseting. Dedaccai (i think so) is experimenting with strange looking tube designs. The concept of splines that run on the inside of a tube originates on the basic principle of gun barrels. Early barrels used to be smooth on the inside . Today's firearms have ridges in order to give a bullet with additional spin initiated energy that adds to the thermal energy from the explosive shell that propulses the actual bullet.As a result the bullet exits the muzzle of the barrel with greater velocity. This has nothing to do with tube integrity strenght or stiffness. The exactly opposite idea with splines instead of ridges however changes drastically the behavior of the tube to the better. The ridges dont have to be running the whole length of the tube, they may variate in volume and construction depending on the application, and they can be twisted depending on the direction that we want the stiffness and torsional rigidity to appear.

Originally posted by math2p14
The facts lie in CORPORATE FINANCE, allow me as a phd student (wiseguy and showoff :D:D:D:D) to say that manitou paid some cash or more probably offered cheaper OEM 1.5 forks to RM/Scott/Orange to accept 1.5 in their frame designs. Other than that...its just business, money make the world go round and its sad but its true. Nobody up there cares about riding/computing/etc etc more than the profitability of a product. They only care about a customer as long as their care is able to produce profits. If the profits are made then no further customer care is needed.

Cheers.

RM had a 1.5 switch for 2003, but if you look at the 2004's the switch's have the Z150's on them. Don't know about Scott or Orange since I haven't heard alot from them lately.

I have ridden a 1.5 switch this year, and I could feel fork flex in the Sherman, head set was adjust properly. While some people will love the 1.5, I don't think there is anything wrong with the 1-1/8. If you want to reduce flex in the fork, Marzocchi is going in the correct direction, thicker stanctions.

Bigger = better!



Just ask your girlfriend :o

Originally posted by math2p14
Today's firearms have ridges in order to give a bullet with additional spin initiated energy that adds to the thermal energy from the explosive shell that propulses the actual bullet.As a result the bullet exits the muzzle of the barrel with greater velocity. This has nothing to do with tube integrity strenght or stiffness.

Actually the primary reasoning behind rifling a barrel in order to spin the projectile is to increase stability in flight and thus improve accuracy.


Originally posted by math2p14
The exactly opposite idea with splines instead of ridges however changes drastically the behavior of the tube to the better. The ridges dont have to be running the whole length of the tube, they may variate in volume and construction depending on the application, and they can be twisted depending on the direction that we want the stiffness and torsional rigidity to appear.

To further make the comparison between gun barrels and bicycle frame tubing, one could look at the fluted barrels on some crew-served and sniper weapons. The flutes allow the barrel to sustain more prolonged and higher rates of fire without overheating and casuing barrel droop. Additionally, the reinforce the barrel to prevent deflection from firing pressures.

i thought Klein made the first over over sized headtubes?

Originally posted by khuon
Actually the primary reasoning behind rifling a barrel in order to spin the projectile is to increase stability in flight and thus improve accuracy.



To further make the comparison between gun barrels and bicycle frame tubing, one could look at the fluted barrels on some crew-served and sniper weapons. The flutes allow the barrel to sustain more prolonged and higher rates of fire without overheating and casuing barrel droop. Additionally, the reinforce the barrel to prevent deflection from firing pressures.

Not only to increase stablity during flight. Also it increases the energy of the projectile due to the torque effects that add to the projectile because of the flutes. The comparison with sniper rifles you made is perfect and i forgot to mention it! Hey are you into sniper stuff as well?

My Gemini has 1.5 but I use a 1 1/8 tube, hence the need to emply reducers to make it fit. I wonder if 1.5 is a solution to a problem that did not exist?

Apart from the Lefty strut (which I believe is 1.5) I don't know if anyone else makes 1.5 tubes as yet?

Or is it down to marketing?

Originally posted by math2p14
Hey are you into sniper stuff as well?

I did a bit of target shooting... not so much anymore as I've sold my guns but I have thought about getting back into it. One expensive hobby at a time though... :D

Well I tried to do a search but there were many many many threads on other boards about the physics behind this topic. One of the main topics that came up was a math formula defining the strenght of the tube based on the circ, depth etc...well this strength increase was there but insignifigant. It might look stronger but it really isn't. Whether or not it is good or bad, don't really care, I think it looks cool :D...

Ironhorse sgs pro has a 1.5 headtube.

Currently, Manitou is the only fork manufacturer making the 1.5 steerer tube.

That's fine with me, since I prefer Marzocchi's.

L8R

The 1.5 head tube exists not to strengthen the fork but to strengthen the head tube/down tube/top tube interface.
Most of the bending energy in a long travel fork can be absorbed by the compression of the fork, Marzocchi proved this.

However 1.5 is still the way forward for long travel single crown forks. It privides a stiffer crown.
Alows for even bigger stantions to be used.
The bigger headset is able to absorb more energy so there are longevity advantages as well.

The main advantage of the std is the bigger front end of the bike.

As for rifling of gun barrels adding energy to the projectile, thats baloney.
Rifling is there mainly to prevent barrel droop on long barrel weapons. It also has the advantage of adding stability to the projectile, increasing accuracy and flattening the trajectory.
In fact there is a slight drop in projectile velocity due to blow by of the expanding propellant gases but this is more than offset by the gain in stability.

Originally posted by TimB
As for rifling of gun barrels adding energy to the projectile, thats baloney.
Rifling is there mainly to prevent barrel droop on long barrel weapons. It also has the advantage of adding stability to the projectile, increasing accuracy and flattening the trajectory.
In fact there is a slight drop in projectile velocity due to blow by of the expanding propellant gases but this is more than offset by the gain in stability.

XTR guns maybe :fun:

Originally posted by TimB
The 1.5 head tube exists not to strengthen the fork but to strengthen the head tube/down tube/top tube interface.

However 1.5 is still the way forward for long travel single crown forks. It privides a stiffer crown.


This was in the same post timb... it contradicts itself, what did you mean? Or are you just confused? :D

Originally posted by slcpunk21
This was in the same post timb... it contradicts itself, what did you mean? Or are you just confused? :D :beer:

if you read the post properly :crash: you will understand that the crown does not necessarily have to be stiffer but having a bigger basis for the crown does open up design freedom to add stiffness and strength in the design process.

The gains in strength of the headtube interfaces is always there. A stronger is not necessary.


Math Shimano make guns TOO!!!!
WOW
Show me I want 1 so i can use it on you......;)

Originally posted by TimB
if you read the post properly :crash: you will understand that the crown does not necessarily have to be stiffer but having a bigger basis for the crown does open up design freedom to add stiffness and strength in the design process.

The gains in strength of the headtube interfaces is always there. A stronger is not necessary.



If i read it properly? what with my contradiction hat on? :crash: (see i can use that too)

Have you ridden the marz fork? have you ridden any other fork with the 1.5 steerer? I'm just curious how you know if marz has proved it's not necessary to make it stiffer? Are you going by what they tell you? Or do you have personal experience and enough ride time (more than a spin around the parking lot) to be able to make these statements.

I'm not saying I'm fore the 1.5 or against it, just wondering where you get all these "facts" from?

Originally posted by TimB
if you read the post properly :crash: you will understand that the crown does not necessarily have to be stiffer but having a bigger basis for the crown does open up design freedom to add stiffness and strength in the design process.

The gains in strength of the headtube interfaces is always there. A stronger is not necessary.


Math Shimano make guns TOO!!!!
WOW
Show me I want 1 so i can use it on you......;)

Sweet. thanks. :beer:

Originally posted by slcpunk21
If i read it properly? what with my contradiction hat on? :crash: (see i can use that too)

Have you ridden the marz fork? have you ridden any other fork with the 1.5 steerer? I'm just curious how you know if marz has proved it's not necessary to make it stiffer? Are you going by what they tell you? Or do you have personal experience and enough ride time (more than a spin around the parking lot) to be able to make these statements.

I'm not saying I'm fore the 1.5 or against it, just wondering where you get all these "facts" from?


I'm not going to get in to a debate with you.
I have tried a Sherman on a Gemini but have'nt tried the Z150.
Guys at my LBS have (at Morzine) and they like it, saying it's plush, not as stiff as Sherman but adequate (and Safe - remember another driver for 1.5 was safety).


heres link to 1.5 site

<http://www.OnePointFivestandard.com>