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  #1  
Old 01-21-2013, 03:11 AM
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a1bummer a1bummer is offline
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Default VW trike steering wobble

Hi guys,
My Dad is building a VW trike with about a late 70's Goldwing triple tree. I took it for a spin and it is full of issues that need to be addressed. The one that bothered me the most was the way the front wobbled. If I took both hands off the bars even for a moment, its a real tank slapper and seems like an accident waiting to happen. Where do you guys think I should start to try eliminating the issue? More rake? Less rake? Different tire size? I've never ridden a trike before, is this a common problem?

Another problem is his brakes. It still has the stock drums and he setup a stock master cylinder in the floorboards. When I hit the pedal, it just doesn't do much to slow the thing down. What should I look for? Are there any aftermarket setups that would be a better choice?

The other problem is the shift linkage. I really have to fight to change gears. How do you guys set up yours? Aren't there automatics out there somewhere? I've heard of the Autostick setups, at least that's what I think I've heard them called anyway, but that would still require manual shifting. How the heck is the shift linkage set up for those trikes made out of bikes with VW rearends?

This thing looks like it should be on a Road Warrior movie, but at least I can try to help make it safer for him to ride. I know I have pics somewhere.

Thanks,
Bill
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  #2  
Old 01-21-2013, 08:45 AM
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Default VW Trike forums

There are quite a few VW Trike forums on the internet. I am sure that it would be the right place to look for info. I have been looking at these for quite a while since I have always wanted to build myself a trike. Guess it will be a hard one to convince the boss that we need one though.

Here are just a few:

http://www.trikespace.com/

http://www.triketalk.com/

http://www.volksrods.com/
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  #3  
Old 01-21-2013, 09:49 AM
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Cool three ways

Quote:
Originally Posted by a1bummer View Post
The one that bothered me the most was the way the front wobbled. If I took both hands off the bars even for a moment, its a real tank slapper and seems like an accident waiting to happen. Where do you guys think I should start to try eliminating the issue? More rake? Less rake? Different tire size? I've never ridden a trike before, is this a common problem?
I've never built a trike, but I've ridden several. It sounds like you dont have enough trail in the front end geometry, but that’s a guess. It maybe that you have too much trail...hard to know by just talking about it here.

Just about all trikes have an inherent 'head-shake' at one speed or another, its the nature of the beast. Some builders add steering dampers, others build in more trail, others simply tighten the steering bearings and let you 'ride through' it. There is more to trike design than slapping on a set of forks and assuming it will be ok.

The other issues sound complex as well, and it sounds like more work will certainly be needed.

Good luck on this!



http://www.timms-trikes.com/steering.html
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  #4  
Old 01-21-2013, 09:58 AM
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Yes front wobble is an inherent issue with trikes. The very first suspect will be the front tire. Unfortunately with motorcycle tires they have a round profile for obvious reasons but with a trike they do not lean in corners so they tend to scrub in corners which cups them making the front end prone to oscillations. If you can find a sidecar tire that will fit the front rim then use that as they will have a flat profile like a car tire.

The rake is more so a function of steering ease. The further out the front tire on a trike, the better the grip when turning. It has to do with the three points of the triangle of road contact...

Steering neck torque and bearing condition are the other contributers/controllers for wobble. With a trike you want tighter torque on the bearings as opposed to looser torque for handling on a 2 wheeler for quick reversing of direction from one way to the other(flipability). With a trike you need them to be more solid as you aren't gonna go thru the twisties at 100mph. Just don't put so much torque on them that you cause excessive stiffness and wear on the bearings themselves.

The last issue is the proper alignment of the 2 rear wheels, but that does not contribute to oscillations as much as it contributes to tracking straight down the road. Check the age and condition of the rear wheels, you do not want to use ANY tire much older than 6 years old for safety reasons...

Brakes. Try to find some kind of disc brakes and get rid of the drums. Braking in itself is a whole science. Bore size of the master in itself is an issue. Smaller bore = more pressure but longer stroke. The pad material is important as is the total contact area. Then you get into heat dispersion and eliminating gasses and material from the pads, the whole basis behind slotted and cross drilled rotors. Slots get rid of the gasses and debris whereas the cross drilling adds to total cooling area of the surface. Also, do not forget the frront brake as it does the larger percentage of braking just like in a car. Same braking issues and rules apply...

Shift linkage, well with the setup you are doing, that is an issue. Keep in mind most of us trikers use the stock motorcycle transmission so there is no difference...
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  #5  
Old 01-21-2013, 10:12 AM
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I had a VW back in the early 70's. The setup you're describing sounds to me like there's more rake needed to create more trail which will civilize head shake thou as noted there's always be some at certain speeds. Normally low speed. If the front wheel is of the spoked type make sure the spokes are tight and the wheel runs true as that can create problems too.
Another soure for info is with the Brothers of the Third Wheel. Here's a link -- http://btw-trikers.org/uploads/home.php
These guys thrive on home builts and will help you.
Larry
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  #6  
Old 01-22-2013, 01:40 PM
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Thanks for your input guys, its much appreciated.

Bill
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