Tuesday, January 29, 2008

Old up-right frames

This is my very first carbon frame, built in 1998. The frame is built over an expended polystyrene foam core (15Kg/m3) with a hot wire and a couple of template. The foam has been bonded to a steel bottom bracket and a steel colomne then every things has been 'locked in place' on a big plywood sheet to keep the correct angles and avoid any warp. Hand lamination has been used.
I must admit that the very first time I tried the frame, I felt that the rear wheel was not always following the front wheel. That was a terrible feeling but it did not break. A layer of 400g at +/-45deg solved the problem. Final weight of the frame is about 1.5Kg, which is not that bad with a couple of steel inserts.
The rear lugs are all carbon and the aft derailleur is taped directly into the carbon.
The complete bike weighs about 9.55Kg as shown on the picture.
The bike is stiff vertically but can twist a lot if you push the aft wheel side ways with your hand. I can't feel it on the road unless I hammer it down.
Wheels are very bad below 40km/h, sensible to side wind and innacurate in corners. Not my best option.

This track frame wheighs 1.3Kg and is heavily reinforced.
I used ACG VTM264 low temperature prepreg to build this frame on an extruded foam core. (styrodur). I also made the oven with a couple of Styrodur sheets and a modified bathroom heater (I removed the safety switch). I used a car thermo sensor to keep 85deg in the oven. The vacuum pump is a modified fridge compressor.
Low temperature prepreg was a very good solution as I could laminate the complete fore triangle in one shot.
Unfortunately, while curing the rear wishbone, the oven temperature reached 110deg, damaging my oven (but no the frame's core)and wrapped the fore triangle which was not supported by any template. My first cure was probably not enough and the resin system reached its Tg again. If I have the opportunity, I will use an other cure to straighten the frame but I have little hope about this method. Try and see!


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