I have been poking around the web looking for a way to add a reverse gear to my project since the motorcycle I am using does not have one built in. I have found some planetary reverse kits for buggies and some for harleys and one for bikes in general. The sets for buggies looks too small as they were advertised for 125cc & 250cc engines. The Harley set is specifically for the Harley, so that's out. The last one is here: http://www.roadstercycle.com/ and is about $1200. Looks like it might be made from Chevy parts, but I'm not sure.
Here is another page in a blog from Dan Lenox describing how he used the planetary gears out of a C4 transmission to add a reverse drive. http://www.briery.com/vortex/reverse_operation/reverse_operation.html
This piqued my interest and I have started doing some research. It looks like it might be possible to get a 1:1 through drive, reverse, about a 30% overdrive and maybe even a granny gear out of this type of a system. Certainly some design challenges, but it looks interesting. I am going to start poking around for a C4 or C5 tranny I can tear down and play with......
Wednesday, March 21, 2012
Monday, March 12, 2012
Swing Arm Debate
There are three approaches that can be taken on the swing arm issue. They are:
1) Modify an existing motorcycle swing arm to accept a larger pivot shaft, add support structure over the top of the wheel to improve stiffness. - I suspect that the dissatisfaction in the final results would off set any real or percieved effort that might result from taking this approach. This is a piece of the chassis that is important and needs to be done right and not cobbled together.
2) Scratch build a swing arm similar to the arm on the Vortex. This solution is probably the stiffest design for the lowest weight. It does make tire changes difficult but that shouldn't be often enough to be a big deal. It also has the advantage the ability to align the rear wheel and tighten the belt / chain drive without shims. Here is a link to one that is very nicely done. http://www.briery.com/vortex/rear_suspension/rear_suspension.html
3) Scratch build a cantilever swing arm (one sided). This would make tire changes easier, but aligning the rear wheel would likely require shimming. Yuck. On the plus side, I think the front hub from a FWD or 4x4 could be used, the yoke that normally connects to the drive shaft could be reworked for mounting the drive sprocket and the stock disc brakes from the donor vehicle could be reused.
1) Modify an existing motorcycle swing arm to accept a larger pivot shaft, add support structure over the top of the wheel to improve stiffness. - I suspect that the dissatisfaction in the final results would off set any real or percieved effort that might result from taking this approach. This is a piece of the chassis that is important and needs to be done right and not cobbled together.
2) Scratch build a swing arm similar to the arm on the Vortex. This solution is probably the stiffest design for the lowest weight. It does make tire changes difficult but that shouldn't be often enough to be a big deal. It also has the advantage the ability to align the rear wheel and tighten the belt / chain drive without shims. Here is a link to one that is very nicely done. http://www.briery.com/vortex/rear_suspension/rear_suspension.html
3) Scratch build a cantilever swing arm (one sided). This would make tire changes easier, but aligning the rear wheel would likely require shimming. Yuck. On the plus side, I think the front hub from a FWD or 4x4 could be used, the yoke that normally connects to the drive shaft could be reworked for mounting the drive sprocket and the stock disc brakes from the donor vehicle could be reused.
Chassis Design - Revisited
This weekend a FireAero went up for auction on Ebay at a GREAT price. Too bad I can't jump on it. One of the things that has been done is a Vortex style swing arm has been built. Using the motorcycle rear end is the one thing that I have been waffling over. On a motorcycle, it will see very little in terms of side loading. On a car, that is not the case.
Body roll and rear end twist are two things that I have been concerned about. Jim Musser's front end design addresses the body roll problem. A fully supported rear swing arm is the best solution for the rear twist problem. Here is a video clip showing the problem pretty dramatically. It is a Venom three wheel car doing a donut. Watch how much the body is rolling to the outside of the turn as it comes around, and watch the twist in the rear end, especially on the first turn before the tire loses traction. http://www.youtube.com/watch?v=xcUjkrh_L_A&feature=related
In light of this, I am considering focusing my initial efforts on developing a somewhat "universal" three wheel chassis. If all of the suspension, steering, final drive and reverse issues are solved, and several standardized mounting points can be provided for the engine, then the task of a builder would be simplified a great deal.
I will discuss the two swing arm options I am considering in another post.
Body roll and rear end twist are two things that I have been concerned about. Jim Musser's front end design addresses the body roll problem. A fully supported rear swing arm is the best solution for the rear twist problem. Here is a video clip showing the problem pretty dramatically. It is a Venom three wheel car doing a donut. Watch how much the body is rolling to the outside of the turn as it comes around, and watch the twist in the rear end, especially on the first turn before the tire loses traction. http://www.youtube.com/watch?v=xcUjkrh_L_A&feature=related
In light of this, I am considering focusing my initial efforts on developing a somewhat "universal" three wheel chassis. If all of the suspension, steering, final drive and reverse issues are solved, and several standardized mounting points can be provided for the engine, then the task of a builder would be simplified a great deal.
I will discuss the two swing arm options I am considering in another post.
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