Well, it took way longer than expected and was a ton of work, but I finally got the new carbon sandwich frame lowracer on the road. The outside perimeter is just a rough cut - I am waiting until I can get an actual fairing half shell so that I can accurately trace the outline and cut it out.
It's a dream compared to the woody prototype frame because it only weighs 28 pounds compared to about 50 for the wooden beast. It is very easy to ride - much like the M5, but with a way larger front wheel. I could definitely feel the wind pushing the frame around, but controlling it wasn't all that difficult. I figure if I can control the frame-only in the wind, then controlling it with the fairing should be a bit easier.
I'm not sure yet if I have enough layers of carbon on the frame. Since there isn't a brake yet, I didn't get a chance to pound on the cranks to see if the frame flexes at all. If I push hard on the crank while immobile, I can see a bit of play in the bottom bracket which I will have to address. The bottom bracket is bolted to the frame with an aluminum bracket. The bolts are moving around a bit in the frame, so I may just bond the BB shell and bracket onto the frame.
Here are some details regarding the last few days worth of work:
|Nicolas Gluondufou kindly produced this FEA study of the frame and torque forces from turning the cranks.
I used the result to plan the last carbon reinforcement layers.
The complete report is at Nicolas's web site
|I traced the reinforcement patterns on the carbon fabric with a grease pen and cut them out.|
|Since the reinforcement layers are flat, I vacuum bagged it for a strong cure.|
|This shows the bottom bracket shell.|
|Note the bracket that fits over the bb shell. Also shown is the bracket that holds the headset and fork.|
|Closeup of the remote steering headset bracket.|
|This is the remote steering bar mounted to the frame. My frame width isn't exact the same as my bracket width, so I am using washers as spacers for now. I'll eventually add another layer to two to the frame to thicken it up so that I don't need the spacers.
The shifter is a Shimano XT mountain bike Rapid Fire shifter. I did not want to use bar end shifters like on the M5 because it's a pain to move your hand down the bar to shift all the time. The trigger shifters are way better because your hands can stay on the bars.
|This is the rear wheel dome bolted onto the frame. I am going to bond one side permanently to the frame and the other side will be bolted on (so I can remove the wheel).
The seat is temporary - just a piece of curved Sintra plastic with foam ontop. It seems to work fine because it rests against the curved frame. It could use some reinforcement on the sides though.
|This is a closeup of the mid drive. James Kenny machined this custom aluminum spider for me. It holds a 55 tooth large ring and a 28 tooth small. It will hold all of the smallest mountain bike chain rings and all of the largest road bike rings - the best of both worlds for big gearing!
The spider still needs to be lightened drilling holes through it.
I can lighten it up further - possibly shaving off 5 or more additional pounds off the 28. First, there is a large area in the nose and tail of the frame that can be cut out. Second, my front fork is very heavy - I would like to eventually make a carbon fork with a carbon steerer tube. Also my remote steering bar is very heavy - it could be carbon with a carbon steerer tube and also - I could probably do away with the headset and replace it with a UHMW plastic bushing. My remote steering push rod is also very heavy and could be carbonized.
Still to do:
1. Add a rear caliper brake
2. Trace the real perimeter outline using an actual fairing half shell (when I get one!), and cut out the perimeter
3. Edge laminate the perimeter
4. Thicken the frame to avoid using the spacers on the brackets
5. Bond in the bottom brackets
6. All of the above mentioned lightening mods
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