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.
Monday, February 20, 2012
Ninja reassembly
This weekend I received a Haynes manual for the Ninja. The bike was in several boxes when I bought it so it should be entertaining to put it back together and get it running. With a 110 mile daily round trip commute, the gas price hikes we are being warned about have me concerned. I used have a road bike, but really don't like the thought of riding a motorcycle on the road after losing some family members to bike wrecks. However, in today's economy we just keep getting backed into a corner financially and have to keep making the most of what we have available.
On the upside, it will be fun putting a bike together. I haven't done that since I as a kid and am excited to do it with my boys if they are interested. My sons are 12 and 15 years old.
On the upside, it will be fun putting a bike together. I haven't done that since I as a kid and am excited to do it with my boys if they are interested. My sons are 12 and 15 years old.
Monday, February 13, 2012
Front suspension discussion: Jim Musser
Today I called Jim Musser, designer of the Sport Cycle and he was very helpful in explaining how the front suspension achieves the very high roll resistance demonstrated in the Sport Cycle. I asked if the stiffness was achieved because
1) the pivoting frame that actuates the shock absorber is positioned across the vehicle, attached to both sides of the frame
2) the two lower control arms are tied together through the linkage.
He explained that the stiffness is a result of the fact that the two lower control arms are linked together. During normal cornering the outside suspension goes into compression and the inside suspension goes into rebound. Linking the two sides together through the shock frame forces the wheels to move together and that resists body roll. The stiffness of the shock frame is also a factor and lengthening the shock frame to fit the wider chassis will likely require some stiffening of the shock frame to resist torsional distortion during cornering. He also mentioned that he originally thought he had invented a unique suspension system but later discovered that some European race cars had also done the same thing.
He also mentioned that the chassis on a three wheeled vehicle does not need to be as stiff as on a four wheel vehicle because all weight transfer during cornering happens only at the front rather than front to back as in a four wheeler.
We also discussed the concern of CG location in a side-by-side arrangement and the asymmetrical CG position caused by a single occupant, resulting in reduced roll over limits. I mentioned that I plan to move the passengers forward a bit to improve CG. He also thought that a two seater would be better received in the market than a single seat. While marketing the resultant vehicle from this effort is in the back of my mind, my primary objective is to complete one for the fun of the project and to enjoy driving a vehicle I have designed and built. Whatever will be will be.
1) the pivoting frame that actuates the shock absorber is positioned across the vehicle, attached to both sides of the frame
2) the two lower control arms are tied together through the linkage.
He explained that the stiffness is a result of the fact that the two lower control arms are linked together. During normal cornering the outside suspension goes into compression and the inside suspension goes into rebound. Linking the two sides together through the shock frame forces the wheels to move together and that resists body roll. The stiffness of the shock frame is also a factor and lengthening the shock frame to fit the wider chassis will likely require some stiffening of the shock frame to resist torsional distortion during cornering. He also mentioned that he originally thought he had invented a unique suspension system but later discovered that some European race cars had also done the same thing.
He also mentioned that the chassis on a three wheeled vehicle does not need to be as stiff as on a four wheel vehicle because all weight transfer during cornering happens only at the front rather than front to back as in a four wheeler.
We also discussed the concern of CG location in a side-by-side arrangement and the asymmetrical CG position caused by a single occupant, resulting in reduced roll over limits. I mentioned that I plan to move the passengers forward a bit to improve CG. He also thought that a two seater would be better received in the market than a single seat. While marketing the resultant vehicle from this effort is in the back of my mind, my primary objective is to complete one for the fun of the project and to enjoy driving a vehicle I have designed and built. Whatever will be will be.
Tuesday, January 17, 2012
Frame layout: Tubing size
Looking at the photos from some of the other vehicles I have been referring to, I am a bit uncomfortable with the tubing sizes that some of them use. My primary reason is because of crash protection.
Jim Musser's chassis is the most attractive to me because it forms some protection around the occupant. The tubing he employed was 2.00 inch square tubing with 0.12 (1/8 inch) wall. I like that, but wondered if there was a readily available square tubing that might be an improvement.
I have settled on 2.00 x 3.00 x 0.084 (14 gage) rectangular tubing. It is about 10% lighter than the 2.00 x 0.12 square tubing, and is about the same stiffness in the 2.00 direction and almost twice the stiffness in the 3.00 direction. Orienting the 3.00 side vertical in the bottom rails and the 3.00 side horizontal in the top rail of the frame should result in a stiffer frame with a minimum weight penalty. A stiffer frame should be better for performance and definitely better for crash protection.
Jim Musser's chassis is the most attractive to me because it forms some protection around the occupant. The tubing he employed was 2.00 inch square tubing with 0.12 (1/8 inch) wall. I like that, but wondered if there was a readily available square tubing that might be an improvement.
I have settled on 2.00 x 3.00 x 0.084 (14 gage) rectangular tubing. It is about 10% lighter than the 2.00 x 0.12 square tubing, and is about the same stiffness in the 2.00 direction and almost twice the stiffness in the 3.00 direction. Orienting the 3.00 side vertical in the bottom rails and the 3.00 side horizontal in the top rail of the frame should result in a stiffer frame with a minimum weight penalty. A stiffer frame should be better for performance and definitely better for crash protection.
Wednesday, January 11, 2012
Design Rationale: 6 - 8 inches ground clearance
The Sport Cycle has about 4 inches of ground clearance. Last summer, I built a Marauder recumbent bicycle as designed by http://www.atomiczombie.com/ It had 4 inches of ground clearance and it dragged when I rode it over the hump where our driveway crosses an irrigation canal. I modified the frame to 7 inches of ground clearance and that seemed to be a good number.
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