Sitting Comfortably?
By Anthony van Someren - 23 Jan 12
As well as posting stuff about pretty bikes and cool events, we want to make sure the Shed is also a useful place to hang out if you're actually building a bike, or want to do a little more than just bolt on a few accessories from Busters or Motrax.
Here, Adam from UMC takes us through the basics on how he builds a seat pan from scratch on the Untitled bikes:
Making a seat pan can seem very difficult if you have never done it before. I hadn't made one until I did my "midlife crisis bike" in 2010. Back then I used 3mm sheet metal which is tough to cut and shape. Now I've leant the easy seat pan construction. Use mesh metal which can be bent and cut really easily. You will also need fiber glass and resin to stiffen it up once you have the shape you need.
Cut round your template and mark and cut your mesh metal sheet. A pair of tin snips will cut the mesh easily.
If your doing this job with most of the bike intact place a plastic bin bag over the subframe and then put your newly shaped seat pan back on top as the next bit is messy.
Before using the resin and fiber glass zip tie the seat pan to the subframe this will ensure it keeps it's shape whist you are working on it.
Mix your resin and apply it to the fiber glass sheet using a stiff brush. Make sure the fiber glass gets really wet and goes almost clear. The resin really needs to soak into the fiber glass and to sink between the holes of the metal mesh to ensure it bonds with it properly.
Once the resin and fiber glass has dried remove the seat from the subframe and add as many layers of fiber glass and resin as required to the top and underside of your seat pan to strengthen it.
Now you have a very stiff and light seat pan moulded to the shape you wanted. Next time I'll show you how to attach it to the subframe.
And here is the seat foam being reshaped...
Place a piece of clear plastic sheeting on your subframe to work out the shape you need. Mark out the shape with a permanent marker pen.
Cut round your template and mark and cut your mesh metal sheet. A pair of tin snips will cut the mesh easily.
Place your metal sheet on your subframe and mould it to the shape you require. If you bend it back wards and forward too much it will snap in half so be careful.
If your doing this job with most of the bike intact place a plastic bin bag over the subframe and then put your newly shaped seat pan back on top as the next bit is messy.
Before using the resin and fiber glass zip tie the seat pan to the subframe this will ensure it keeps it's shape whist you are working on it.
Use your plastic template to cut out a shape in the fiber glass sheeting - place it over your metal mesh ready to be resin soaked.
Mix your resin and apply it to the fiber glass sheet using a stiff brush. Make sure the fiber glass gets really wet and goes almost clear. The resin really needs to soak into the fiber glass and to sink between the holes of the metal mesh to ensure it bonds with it properly.
Once the resin and fiber glass has dried remove the seat from the subframe and add as many layers of fiber glass and resin as required to the top and underside of your seat pan to strengthen it.
Now you have a very stiff and light seat pan moulded to the shape you wanted. Next time I'll show you how to attach it to the subframe.
And here is the seat foam being reshaped...
