Thinking about building a trike

531blackbanshee wrote: i think keeping the muffler level will be the most aesthetically pleasing

leon

Thanks Leon! Yeah the axle running across there makes it a necessity. I'm in Vail, CO until Thursday evening. I'll get some more picks up this weekend.
Bill

Even though I haven't yet made up my exhaust system I couldn't resist and went out for my first ride today. I learned quite a lot. Head pipes are LOUD. I need a stiffer front fork. Also need a steering damper if the new fork can't give me less trail. I also learned that I need a larger rear master cylinder. The 5/8" unit that came on the bike just can't handle the four pistons on the back brakes. Any body have any suggestions?
When one of the rear tires goes over a bump the roll on the frame causes the front end to wobble. Even though I was only going 20 MPH I could feel a harmonic tank slapper in the making.
My Wife shot some video:

Bill

Would lowering the rear help?
Steve

swest wrote: Would lowering the rear help?
Steve

Lowering the rear would increase the trail. How would that help?
Bill

I was thinking it would slow the steering down a little like extending the forks.
Steve

www.chopperhandbook.com/rake.htm
trikerdon.50megs.com/raketrailtrike.htm
Is that the front tire that the bike came with, have you tried truing it?

swest wrote: I was thinking it would slow the steering down a little like extending the forks.
Steve

Hi Steve,
Trail affects a motorcycle front a lot like a tiller on a boat moves the aft end of a boat, port and starboard. Trail is measured by projecting a line through the center of the stem bearing to the ground and dropping a plumb line from the center of the front axle and measuring the distance between the two. The larger the trail number the higher the required steering force is, at least at low speeds.

When I rode over some bumps in the asphalt yesterday, with only one rear tire, the bars were forcefully pushed left and right. I'm thinking, and of this I'm not a 100% certain, that less trail would mean less turning moment on the bars when traversing uneven pavement.

I did finally find a solution to the brake capacity problem. For some reason, probably cheap Chinese parts, the calipers would not self adjust to the disks. I took off the calipers and with a 1/16" shim between the pads I was able to advance the pistons so that the pads were closer to the disks when at rest. I'm hoping that once I adjusted the pistons they will be able to keep up with the pad wear. I seem to have good pedal, at least for now.
Bill

bluej58 wrote: www.chopperhandbook.com/rake.htm
trikerdon.50megs.com/raketrailtrike.htm
Is that the front tire that the bike came with, have you tried truing it?

Hi BJ,
You're right, that's the original tire and totally leaky forks that were on the bike when I got it. I'm not even sure if the inflation is right.
Thanks
Bill

If you hold a bicycle by the seat, and push it along, you can steer it by leaning it one way or the other. It even makes the handle bars move accordingly. Your rear end is essentially doing the same thing if only one rear wheel goes over a bump... it leans the bike toward the lower side. This puts the contact patch of the front wheel off center so the drag of the contact patch tries to turn the bars.

This is only the initial, momentary headshake. The tank slapper effect is likely the result of the rear end oscillating during it's recovery to it's normal position.

The same thing (headshake) happens on a motorcycle. If you accelerate hard over some uneven bumps, and one of the bumps is off center from the tire, it will pull the wheel in the direction of the bump.

So there are actually two things going on. Headshake, which is momentary, and tankslapper which is due to an oscillation. They both have different causes and will require different cures.

The headshake can often be mitigated through things that slow down the steering like more trail (more rake on the forks), longer wheel base, and even steering dampers. More trail lessens the effect of the off-center drag pulling the wheel off center. Basically, think of a chopper front end. Steering dampers are for headshake, even though they can lessen the effect of a tankslapper, they are not the cure for a tankslapper.

Tankslapper is often from an oscillation in the rear end. On a motorcycle it can be from worn parts (swingarm bearings etc) and often from a worn rear tire. The wider the tire, the worse the effect. The wider the rear tire. the more leverage it has to yaw the bike left and right. If the parts are worn, there is even more slop which lets the rear wheel generate more momentum in it's oscillation.

The fix for tankslapper to use much more bracing to solidify the rear end, including the swingarm connection to the frame. The more flex and slop there is, the more intense any oscillation will be.

The above is what I've learned after having a 100mph tank slapper getoff. These two books are some of the references I used.
I hear Tony Foale's book, mentioned in BlueJ's link, is really good, but I haven't had a chance to look at it.
www.amazon.com/Motorcyle-Tuning-Chassis-...binson/dp/075061840X
www.amazon.com/Racing-Motorcycle-Technic...n+bradley+motorcycle

I've been seeing some Honda Goldwings converted to trikes like yours, very professionally, and I'm not sure if they are doing anything to the front end of the Goldwing, but it may have already been pretty much setup to be slow & stable since it was expected to carry a huge load. The Goldwing forks look to be at a pretty good angle, but it's hard to tell what the trail really is without seeing the bike naked.

I can't find any naked photos of the rear end to see what kind of bracing they used, but I'm sure it's probably going to be pretty stout.

As mentioned in BlueJ's link on trikes, with a front engine trike (as opposed to running a VW rear end) you won't be able to put a huge amount of rake on the forks unless you go to a different type of front end. Sliding tubes are not really meant to work horizontally, though some choppers have them, but you can probably get more than what the Kz came with and still use the stock forks.. Also, the correct way to get more trail/rake is to mod the frame. As BlueJ's link shows, it's a bad idea to use the modified triple-clamp to get more rake, as it actually creates less trail (the opposite of what you are trying to accomplish). I know you are fine with cutting and welding, so it's probably not concern for you, just thought I'd mention it in case you might experiment with it.

Looking at the Goldwing and other full size Trikes makes me wonder if More weight ( Mass ) would help with handling issues ???

Or changing the ratio of unsrung weight could be a factor. Just thinking out loud :blink:

Dave

Hello KZQ. You seem to have your understanding of trail back the front, what you want is more trail, lowering the rear will do exactly that, more trail will make it more stable, modern race bikes have around 3.75 to 4 inches of trail so they steer quite quick {leaving rake out of it for now}, choppers have trail in the 5 inches + range, making them very stable , its ok, lots of people get this wrong, Lowering the rear will alter rake in relation to the ground also, adding a degree or too, this will also help make the front more stable, if you are still worried and want piece of mind, fit a steering damper as well....

Cheers