Disc brake parts, spindles & wheels

The rear swing arm, wheel and caliper have arrived! I think the conversion will be pretty simple. Welding a truss that arches over the rear wheel to increase torsional stiffness will probably require cutting the bike frame just behind the middle part where the engine & swing arm mount. Should work out fine. Also, the axle that came with it is bigger than the one that came with my "basket case" so I think it will be fine.

Picked up the Mustang II spindles and a couple of nice wheels to go on them from a wrecking yard. I opted to stay with the 4 bolt hubs since the rotors looked to be in good shape and some decent wheels were available. I plan to rebuild the calipers and replace the wheel bearings & seals.

I plan to separate master cylinders for the front and rear brakes. Balancing will be accomplished with an bar between them that will allow moving that attach point for the linkage to the pedal. The Indy Cycle used Ø5/8 bore cylinders. Out of curiosity, I have put together a spreadsheet that takes into account the area of the brake pads, the arm length from the center of the pad to the axle and the cylinder size difference of the front vs the rear caliper. Also considering the fact that there are two brakes in the front and one in the rear. Ignoring differences stemming from the brake pad materials, I want to get a rough comparison to the front and rear brake system from a purely mechanical standpoint to see what size(s) the two master cylinders should be if I use Ø5/8 bore for the rear one. I am shooting for a 60%/40% front/rear brake balance as an estimate to start with.

Rear swing arm - Got syrup? I've got Waffles

Due to the difficulty in scaring up funds to get this going, I have decided I can save a bit of money by using the Ninja frame and swing arm. I think I can overcome some of the twist issues by beefing up the pivot pin and adding a truss across the top of the swing arm. I am also going to resort to either the Fred Flintstone or Huck Finn methods of reverse for now.

I have ordered a rear swing arm and everything attached to it from a 2009 Ninja EX500. It has disc brakes instead of the manual drum brakes on the bike I have now. I think it should bolt in. I hope. Having hydraulic brakes will make it much easier to balance the brakes after I am done. I may make a new read disc and caliper mounting bracket though. Increasing the diameter of the rotor would give the rear brakes more stopping power than stock without a major system change. The faster rotor speed would probably wear pads a bit faster, but that seems to be a fair trade off.

I will post pics of the conversion at some point.

Rats.....

I went to pick up the front spindles last night and it was a newer mustang with front struts instead of the Mustang II type with upper and lower control arms like I need. Guess I'll just have to man up and go the the local wrecking yard.

Waffling - again... and gathering parts

I am leaning back toward building a two seat tandem design. Glad I'm not actually cutting any metal yet and don't plan to until I have the basic parts gathered up. Yesterday I received a rack & pinion off of a 1976 914 Porsche I purchased off of Ebay. I sniped it for a great deal (I love doing that!) and am happy with its condition. I have located the front suspension off of a mid 80's Mustang at a local wrecking yard that I hope to pick up next week some time. I will be using the front spindles, calipers & rotors. I am still looking for wheels, parts for the rear swing arm, and another caliper and rotor for the rear wheel. I will also need to gather up some misc hardware parts and a couple of adjustable shock absorbers. I think at that point I would be ready to buy some tubing and put the chassis together. Seems like I usually start these projects too soon and stall out waiting for the $$ to buy parts. I am hoping this time that buying parts first will help me to finish this project.

Reverse Gearbox

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......

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.

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.