Hydroforming - A Few Questions

[Egg Fried Rice]

Ello peoples

right, im writing an essay on manufacturing techniques and amazingly, the topic is about hydroforming! ha!

So i was wondering if you guys can help me on a few things i would like to know. I already know how it works, what is it etc but one thing i would like to know is - Why would hydroforming be used in trials bikes? Does it make it stronger and how?

I know its kinda cheeky to get people to help me with my essay but i'm only asking for help

[ogre]

obvious one would be the aesthetics, think of the boxx.

[Matthew_Gibson]

http://en.wikipedia.org/wiki/Hydroforming

any help??

[2sixstreet]

Hydroforming can be applied to many things but since you understand its principles you will realise its not viable to every industry. It definitely leans itself to mass produced items like sub-frame components (complex tubular/box section shapes) in the auto industry. It basically comes down to volume. For the one-off dies, extreme pressures and material costs you want to churn out thousands of the same part to recover your setup cost - good for cars, not so good for trials. I think Giant were one of the first bike companies to use hydroforming and as you know they are a dime a dozen. Correct me if wrong but Specialized and the like all followed - all big name, big volume companies. I can't see our Peruvian friend adopting it any time soon for example. The benefits are volume driven.

Ignoring the cost and if parts could freely be made to any shape the advantage is certainly strength. I'll use the downtube as an example where it joins the headtube. Typically for alloy frames a gusset is introduced here for strength. Consider the time and effort to make a tube, weld it on, make a gusset and weld it on, repeat. If you can hydroform a single piece with this strength built in then its much faster for production without adding parts for strength. Saves weight as well. I'm not sure how they maintain wall thickness on hydroformed parts but would imagine it would be consistent. You can essentially design a part to any shape you want first go with the maximum benefit - FEA would be handy here.

Not sure what level you're at or how in depth you need to go but you could make a simple spreadsheet showing a manufacturing time scale for single components. eg a semi-trailing arm for a car made in one piece vs fabricating it from a few bits of pressed steel. You have to add bosses for pivots, cross bars, mounting points etc plus welding and setting up in a jig - the hydroformed one just needs a bit of post machining and it has maintained its shape every time. Bike frames have less time advantage.

It comes down to the old rule for just about anything. Cheap, Strong, Light - pick 2.

I hope that gives you a bit of food for thought and you can expand on it.

[JonMack]

Don't trust Dave he's full of shit (and shrimp, kangaroo meat, wallaby, etc.)

Love you really!

[Greetings]

I think it'd be wiser if you had a look on google and wiki. Although you've received a very good answer, most of us can't provide you with helpful information since few of us have the right education.

Here's some basics on HF: http://en.wikipedia.org/wiki/Hydroforming

[2sixstreet]

Don't trust Dave he's full of shit (and shrimp, kangaroo meat, wallaby, etc.)

Love you really!

Thanks mate, havent had a good roo steak for years and now I want one! Wallaby tasted like shit but you can eat it right Mick?

Where have you disappeared to these days?

[bendy]

forging has the advantage of an orientated grain structure and I would guess that hydroforming has the same advantage this can make a component stronger in a certain axis.

the reason for using hydroforming over forging is the high cost of dies. would you be able to posy the essay after you have written it I would be quite interested in finding out more about the process.

[Egg Fried Rice]

forging has the advantage of an orientated grain structure and I would guess that hydroforming has the same advantage this can make a component stronger in a certain axis.

the reason for using hydroforming over forging is the high cost of dies. would you be able to posy the essay after you have written it I would be quite interested in finding out more about the process.

ahh nice!

thanks

yeah sure will probably be about next week sometime

[Matt Burrows]

the reason for using hydroforming over forging is the high cost of dies.

How would you forge tubes long and thin enough to be used for bike frames

Dave explained the main advantages well I thought, its certainly not the cheapest way to make an individual tube but on a large scale it starts to make a lot of sense.

[Bionic Balls]

as above...forging is clearly not practical! bicycle tubes are extruded through a "plug-butting" device...yes, it sounds very wrong.

The oriented grain structure is not really an issue- however, you could say that the tubes will not be affected by the heat generated through welding them together..which is good.

[mafu26]

i think it helps with the dispersion of stress too. so when you apply force to a tube the stress will disperse in a certain way. depending on the application you can then beef up/change the shape of the tube (hydro forming) so it can handle the stress better.

try and find some 'manufacturing process' text books online. 'economies of scale' which i think the other lad at the top touched on.

[durkie]

my understanding has been that hydroforming helps disperse stress simply by increasing weld area at joints. I can't think of any examples of structural hydroforming that aren't at a tube junction.

it seems analogous to (as everyone knows) why they glue critical portions of airplanes together instead of bolting/riveting them - you want to distribute forces over as large an area as possible, and if you use bolts, you have basically several small points where forces are distributed, whereas with glue you have forces transferred over the entire area of the glued portion.

[Mike Poyzer @ Onza]

Hydroforming really only gives a greater choice of the more custom looking tubes, unlike those generally used on bicycle frames. Round or symmetric extruded tubes give a limited choice of styles. Hydroforming gives a much greater choice. As has been said, for the limited runs of Trials frames, the cost is prohibitive. However these days many frame companies have invested in the tooling to produce "stock" shapes. You can thus select a hydroformed tube which can be adapted to your particular frame design, without any major investment. This is what we did with our Cleaner Frame and what we are now doing with the new Limey.

[2sixstreet]

as above...forging is clearly not practical! bicycle tubes are extruded through a "plug-butting" device...yes, it sounds very wrong.

The oriented grain structure is not really an issue- however, you could say that the tubes will not be affected by the heat generated through welding them together..which is good.

Yep forgot about that point. The less welding you need to do with a one off process using a hydroformed tube makes it less susceptible to weld stresses and heat affected zones etc.

[PaRtZ]

Ill try and copy some information from my uni. They'ev just installed this program (CES material selection or something) Ill see if hydroformed is included

[bendy]

How would you forge tubes long and thin enough to be used for bike frames

Dave explained the main advantages well I thought, its certainly not the cheapest way to make an individual tube but on a large scale it starts to make a lot of sense.

you can forge a massive range of shapes (admitedly not hollow so tubes are out) but sections as long and as thin as the tubes used in bike frames are possible to forge (look at the thickness of a crank shaft in compassision to its length.)