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Wednesday: Now the wheels have fallen off again. Not quite literally, but close. The Connect BB is a simple axle with two bearings and a loose sleeve trapped between them. The bearings are unsupported externally unless they are housed in a close fitting tube and trapped between the threaded end cups. I was clamping at only one end cup which is a bit unfair.
As I was cranking the dome around the outer, unsupported, bearing became loose. There followed a search for a suitable length of tubing to house the outer bearings.Which task, as donor, eventually fell to an old Nilfisk vacuum cleaner tube. I used enough length to hide inside the 2x4 as well as to contain and support the bearing.
The dome returned to flying around effortlessly thanks to my cranking. I had added a 5kg weight to the far end of the, now much shorter, 2x4. This proved adequate except when the weight dipped and rested on the octagon's top ring. So I need a more compact weight than the disk I used on edge. It couldn't lie flat because there just wasn't room.
Then I remembered an old, iron, 5kg, conical scale weight and fixed that to the 2x4. Much better looking and it maximized the moment.[Mass x distance from pivot.]
Then I remembered an old, iron, 5kg, conical scale weight and fixed that to the 2x4. Much better looking and it maximized the moment.[Mass x distance from pivot.]
It kept raining on and off so I had to keep closing the shutter doors. Which meant I needed artificial light without wrapping the cable around every obstacle in its path as I cranked the dome around.
I still have a couple of problems to solve. The pivot in the 2x4 is too lose and getting worse. I can use the original needle bearing from the friction roller to fix this.
The other problem is the BB bearing housing twisting in the 2x4. Just my luck to buy a BB which is not one sealed unit. The support tube I added is already loose in the 2x4. I wrapped it tightly in electrical tape but that didn't hold for long. I shall just have to add a short length of 2x4 onto the face of the 2x4 lever to better support the tube.
Thursday: Bought a Shimano BB @ 127.5mm with a hopefully better bearing retention. It doesn't rotate with hand pressure so there may be hope. I shall retain the bearing in the stub of steel tube from the start but clamp it firmly this time.
Friday.: A wet day so I should get on with modifying the lever. Instead of which I spent the day shopping.
Saturday: Another wet day but I fitted the needle roller bearing and its sleeve to a 26mm hole bored in the 2x4. This provided the rigid pivot base I needed to keep the friction roller aligned with a tangent on the base ring. I rebuilt the crank/roller bearing using the Shimano BB. Now the drive roller worked as expected without slipping or steering the dome sideways.
I made a new friction wheel bush, from another left side crank. This time with a large flange to stop the bush from sliding inside the wheel bore as had the original. I even made a slight taper to ensure the wheel locked itself into the bush.
Cranking is almost effortless and can move the dome from a crawl up to high speed in full circles when required. The 6.5:1 lever ratio provides over 30kg of force at the friction roller interface. The cut down plastic, bicycle pedal provides an excellent and comfortable grip as a crank handle. Being plastic it avoids having to handle a cold, metal handle.
I still have a couple of problems to solve. The pivot in the 2x4 is too lose and getting worse. I can use the original needle bearing from the friction roller to fix this.
The other problem is the BB bearing housing twisting in the 2x4. Just my luck to buy a BB which is not one sealed unit. The support tube I added is already loose in the 2x4. I wrapped it tightly in electrical tape but that didn't hold for long. I shall just have to add a short length of 2x4 onto the face of the 2x4 lever to better support the tube.
Thursday: Bought a Shimano BB @ 127.5mm with a hopefully better bearing retention. It doesn't rotate with hand pressure so there may be hope. I shall retain the bearing in the stub of steel tube from the start but clamp it firmly this time.
Friday.: A wet day so I should get on with modifying the lever. Instead of which I spent the day shopping.
I made a new friction wheel bush, from another left side crank. This time with a large flange to stop the bush from sliding inside the wheel bore as had the original. I even made a slight taper to ensure the wheel locked itself into the bush.
Cranking is almost effortless and can move the dome from a crawl up to high speed in full circles when required. The 6.5:1 lever ratio provides over 30kg of force at the friction roller interface. The cut down plastic, bicycle pedal provides an excellent and comfortable grip as a crank handle. Being plastic it avoids having to handle a cold, metal handle.
Click on any image for an enlargement.
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