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geo.tatum
USA
5 Posts |
 Posted - 10/24/2018 : 02:51:11
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Anyone have experience with Shimano 3-9 speed internal geared hubs?
It is nice to spend the evening reviewing old data, inventorying and cleaning up old stored parts, and planning the new machine.
An end goal test of the new project to perform another drag test between the new hull, dubbed WBSS (WavebikeSS), and the old. So pretty much all the drive train and the fins and such will be identical to the operational 20-foot Traveler Wavebike, just the hull form changes in dimension. It keeps the same ogive underwater shape. I am using the program Draft-sight to create the hull plan. Since I will only build one of these things, it is not necessary to construct production molds. The method I have selected to use builds the hull in sections, 6 in all, in watermelon sized cross slices. For this I plan to use structural 2” urethane closed cell foam. There is the stern hull, the mid-section hull, and the bow bull. These slices really do look much like half watermelons on the outside, but the slice insides can be rather intricate in places along the mid and stern sections, as they must include penetration through-hull support. Then I will construct the deck, which is a bit more like artwork. There is a waterline plane that divides the model between hull and deck, and that plane allows me to build the sections registering to the plane, on a long flat table. To jig out each hull and deck slice, I will spray-stick a 1:1 print out of the cross frame on the foam material. The print includes several centerlines as well as a few dowel holes. Then I cut the lines on inside and outside with a fine table jig-saw. Then the slice gets a black pigmented thin glass skin on its faces, as well as a fine ink etch line indicating keel centerline, and its frame number. Then all slices making up a hull part get aligned, doweled, put under compression and glued together on the flat table.
I plan to build the bottom bracket strut and rudder fin into the shape of this hull form, as well as provide a boss for the strut(the strut will be a separate bolt on part), and a boss for the water leg system attachment point. The deck of the WBSS will be much more elliptical in shape than the old Traveler bike, save the areas the operator needs to stand, and the portion that must land the water-leg system. The shape of the old Traveler’s deck was sharp and functional forward as it was designed sheer water away quickly off the bow, and there was some free-board gunnel added to help with displacement changes, such as change to a larger rider, or even taking aboard provisions or a passenger on the bow. But these flat surfaces sometimes introduced wonky forces when in large surf. The deck on the WBSS will be a more of a continuum of the round shape of the hull, so in the effect the hull is attacking the water at some extreme angle and ends up being submerged, there will be no flat-spots or deck shape for the water to act upon to induce any surprise hull rolling force. Since the final part, deck, bow or mid-section will be skinned as a unit, there will be no visible deck hull joint or seam in final part.
The shafting will be some 4+ feet longer on this machine than the Traveler. The Traveler’s drive shaft was a two-part unit and had two guide bearings in either end of the shaft through-hull shaft tube. It never had a free-hub so was much like a track bicycle feel when clipped into the pedals. The additional length of shaft of the WBSS, need for an additional helper bearing, and the fact that the stern section uncouples for transportation and storage, seems to require a coupling point to be able to quick-lock into the mid-section’s drivetrain output shaft (which will be once again, an Alok 90-degree, 1:3.33 transmission gear box). I have no experience with the new Shimano speed sealed internal geared hubs, but it seems to have excellent reviews. My hope is to use one of those components on a flange, to begin the connection for the drive shaft. I think the freewheel will be much appreciated, and it would be nice to be able to keep constant cadence throughout the water-cycles effort range. Since I need to repurpose the geared hub into an in-line transmission, with one shaft connecting to where the chain gear was to be, and the other to the drilled spoke flange, I have some real creative thinking to do. The connection point will certainly feature some very large tubes for coupling, but that might be a benefit. Need one with a non-spinning flange part, which can easily be worked into a strut that is a part of the stern section. It would be nice if it were sealed, full of oil, and made from something that will not rust.
I will soon put two of the old Travelers, or perhaps one of the travelers and the old Peedobike back into action. I sure enjoyed the bicycle ride I had today on the Parkway here in Yorktown VA, looking out over the York River and imagining riding my bike on the water again. Life certainly is full of twists and changes, and it is nice to revisit old ideas and efforts that unlock so many fond memories.
george walter tatum |
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fastwes
USA
2 Posts |
Posted - 12/13/2018 : 17:12:24
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George,
If you wish to do any hot wire section cutting as Rutan pioneered for moldless composite construction, perhaps I could help you. If you have cross sections at the multiple stations in cad form that can be converted into a DXF I can cut thin plywood/luan/hdpe on the 2D cnc router I program and run at work. Even to just hand cut as you described, a harder more substantial pattern material might work better than paper. I can cut up to 4ft by 8ft size held down by vacuum on a porous spoilboard. Perhaps there are other near flat mold or fixture pieces out of 3/4 hdpe I could help you with. No cost no strings attached, I respect what you've done.
Wes Gilbert in CT |
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Bike Building considerations
