Shape forming

[andy m]

I am looking for some type of material that is used today to form shapes/ moulds for formers to make templates from. Eg if I wanted to make the shape of a motorcycle fuel tank before templates were cut as you see when they used to make shapes for cars etc before CAD etc. Years ago it may have been balsa wood, as I am not in the know I think things must have moved on so is there anything readily available??

Thanks...

 

[hotrodder]

I've probably got the wrong end of the stick but are you talking about station bucks? If so then wood is still the usual suspect. To pull a mold off a buck (as opposed to freehand shaping metal to fit it) or to get a 'solid' representation then you can stuff polystyrene blocks into the spaces between stations and carve that... the number of stations is dictated by the shape. Other materials include wire/metal strip frame and chicken wire + bondo or plaster etc

If you're copying an existing part then another way is flexible tape patterns in conjunction with profile/contour gauges... http://www.youtube.com/watch?v=z05Zw65GQp4 On a larger scale than needed for bike tanks contour gauges 'become' http://www.faybutler.com/sweeps2.htm

 

[graffian]

If it's just to get the shape and see what it's like, polystyrene might be OK.
I have made bike tanks using the blue polystyrene, you laminate it to get a decent block, using PVA to stick it together. You can cut and sand it.
It's best to try and avoid having your cuts go through PVA if you want to sand it to shape. I got the foam from a large builder merchants, they were happy for me to take a car full of the broken sheets away.

 

[dannymac]

If its for a one off part you could shape the part in wood / plaster / foam and make a hammer form from fibreglass or even cement and beat it into shape,i think even today with all the cad/cam ,some parts are shaped and designed using "school" clay over a wire base,but using cad routers for doing the donkey work!For a shapley bike tank id use foam,Im assuming youre needing it as a reference for the final metal shaping?

 

[andy m]

Hi yes, I'm looking at ways of forming for fuel tanks, then templates can be made for cutting the sheet. It is at present a homework type thing as I have just started a welding course so I aim to tig ally eventually. Also looking at other items but not as technical..

 

[Lawnmowerboy]

I've seen people use oasis (not the drink) for things like this.

 

[cardiffrob]

There is a 2-part foam mix used for filling the **** end of a Canoe so junior cannot sink when he rolls it. I was given a few tins of it some time ago and it was placed in a plastic bag where it starts to foam after about 2 minutes. Made a blob big enough to mould an aeroplane cowling front end.
A bag might be a handy way to make a fuel tank shape.

 

[andy m]

There is a 2-part foam mix used for filling the **** end of a Canoe so junior cannot sink when he rolls it. I was given a few tins of it some time ago and it was placed in a plastic bag where it starts to foam after about 2 minutes. Made a blob big enough to mould an aeroplane cowling front end.
A bag might be a handy way to make a fuel tank shape.

Thanks, any idea what it's called ??

 

[cardiffrob]

No, but if you type 2 part foam into Ebay it will give some ideas.

IIRC it has a 50:1 expansion ratio. No sealed containers!!!

 

[cardiffrob]

Maybe this geezer can offer some advice???

http://englishrussia.com/2008/05/29/lithuanians-and-pu-foam/

 

[KemppiFrog]

No, but if you type 2 part foam into Ebay it will give some ideas.

IIRC it has a 50:1 expansion ratio. No sealed containers!!!

If it is the same as the one we used to fill spaces on boats, it is an icocyanate. So beware of the fumes, very toxic.