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| tom osselton:
That seems like a big turning radius any tighter and the wheel would be off the ground! I wonder if the motor/rear wheel could turn with the front a few degrees to improve the radius. |
| Lykle:
Yeah the problem with tilting the front wheels completely in sync with the body is wheel scrub. If you use conventional suspension like top and lower wishbones, the wheel needs to scrub sideways when it bumps or droops. That gives a very bad feeling to the driver, the feeling of grip is never certain. So, to avoid that you need to use parallel swingarms, like the VW Bug front suspension. And that is ugly, hard to hide and the range of motion can be hard to achieve. I played around with that in my first designs, when I was still thinking of building it like a car, with airco etc. See my blog about it at http://lykle.tumblr.com. You will have to go way back tho. With a tilter, the steering radius is often the issue. This is why my wheels just tilt a "token" bit and use the conventional wishbone setup. |
| Lykle:
Further work on the bearing stack inside the main rotating tube. I am a bit concerned that by welding the vertical pipes, the main tube will be distorted too much for the bearings. Also, I don't want to use thick walled tubing just for the bearing pockets. Besides, there is no way I can create an accurate bearing pocket inside the long tube of the main frame. So I have designed a few cups to hold the bearings and these cups are welded into the main tube. They are thick enough to withstand warping. Through this all runs a 20 mm shaft that is welded to the axial bearing holder or cup. I have 1 axial and 2 radial deep groove bearings set up. Now, the total length of the 20 mm shaft is 200 mm, so I doubt if the front bearing will actually handle a large radial load, but this way I know for sure that it will all align. Any comments on the design so far? |
| Lykle:
Next step, finalising the various components. This is a pic of the main frame. It is changed a lot since the last image. There is space built in for the battery pack, the bottom side rails are now curved (that will be a nice little challenge to do) and I have added an extra center rail, for stiffness. The two bottom rails on the outside alone would have been to flexible. If I can find the right material, the frame will be made with CroMolly tubing, but I doubt if I will be able to find it here in Cyprus. Certainly not in the various dimensions I want. So I will probably have to re-design it after I find out what I can get around here. The only real worry I now have is the front wheels. Because they do not tilt (or at least only a little) they are subject to sideways forces. Bicycle wheels are not designed to do that. So I might have to work on that. I see two possible solutions. a) design stronger wheels, use standard components like the rim and design a wider hub with more axial load. b) simply find stronger existing wheels, mountain bike wheels perhaps. For the rest of the design work, it is virtually done. The only tweak I am considering for the frame is related to the hand control stalks. Currently they are welded on, but I think I will make them removable. This gives me a little more flexibility to change them in size, functionality and position later on. For instance, the throttle. It is a twist throttle, but I might want to change that to a type of joystick throttle, or a lever like in the fighter jets. Combine it with braking, forward is throttle, backwards is braking. Ok, back to the drawing board. |
| tom osselton:
I'm wondering about that main bearing tube. It seems to me in a front impact you will be forced into a right angle protrusion, can it be shortened for a less damaging angle? |
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