May 11

May 11, 2006

Re-worked landing gear

I pulled the landing gear apart the other day to see what it would take to extend it by about 1/2 ". The reason is that if I 'land' with all of my weight to the right, CriticalPower 'could' tip right over the landing gear wheel. It's not quite extended far enough to be as stable as I would like. So, I took a close look at it as saw a small crack in the carbon new the top of the leg.

In order to have it extend an additional 1/2 ", I needed to move the cable terminator bolt up the leg by a half inch, and that would have been right where the crack was. So I decided to beef the leg up.

First, I reinforced the top of the carbon tube with a wrap of carbon on the INSIDE of the tube. The reason I couldn't reinforce the outside was because the tube slides into another tube that is built into the frame. Here are the exciting details:

1. I wrapped a layer of carbon fabric around the inside of about the top 3 inches of the tube, then wetted it out with epoxy resin and a small paint brush.

2. In order to get the inside wrap to stay on the inside of the tube, I inserted a balloon and inflated it. The balloon acts as sort of a reverse vacuum bag. When the balloon is inflated, it presses the wet carbon liner against the inside of the carbon tube.

3. I used fast setting catalyst and a heat gun to get the epoxy to cure right away.

4. Then I drilled a new hole for my cable terminator bolt and inserted it, along with the nut on the inside of the new reinforced tube. I coated the threads of the nut with grease first.

5. Then I mixed up some micro balloons and epoxy and dumped it into the tube, filling the entire tube up. I taped over the bottom of the tube so it wouldn't leak out.

6. The epoxy kicked SUPER fast because large volumes of this stuff cause major exothermic reactions. The carbon tube was too hot to touch!

7. I unscrewed the cable terminator bolt and it came out easily because of the grease on the threads. Now it screws into a nut that is epoxied into the inside of the tube, as well as threads in the micro/epoxy fill material.

8. The landing gear strut slides into the sleeve in the frame and the cable bolt is screwed back in.

9. I used to have a bungie cord inserted all the way down the landing gear strut, but now my strut is solid, and a short bungie cord won't work. I had to change the whole way the elastic retractor worked because to retract properly with the right amount of elasticity, you must use the entire elastic range of a 10" long bungie cord.

To accomplish this. I attached a nylon cord to the end of the landing gear strut which runs through a short curved piece of plastic tubing and then is tied to the bungie cord which is fastened to the frame above the rear wheel.

10. The other thing I needed to do was make a new bracket for the retractor cable handle. When you pull the handle and retract the landing gear, you are stretching the elastic bungie cord. By sliding the handle behind this bracket, the tension in the cord keeps the wheel retracted. The bracket needed to be slightly adjustable, so I cut slots in it for the bolts.
11. Here is a shot of the landing gear extended.

This is me after my first 100 miler of the training season. It was a great day - sunny and my legs felt strong. My SRM data show that I am in far better shape than last M5 training season! For this 6 hour ride, I spent most of my time at 170 watts and only 115 bpm heart rate. The exact same ride from last season (I found 5 of them), all averaged less watts with heart rates in the mid 120's. The PWC150 from the SRM software calculates what my wattage would be at 150 bpm and it's a useful indicator of your efficiency. If the number goes up, then basically you are producing more work with less effort On average, my PCW150 from last year on long rides such as the ride I did today was between 230 and 250 watts. Todays PCW150 was 303 watts which is very close to my triathlon bike data.


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