"Springer" frontend... needing any info on em. Do's n dont's for design...

[Half-breeder]

As some of you know... I am amidst on a build of a very custom'd trike. The 'design' of it is common enough... but, being a "1-off maker/lover", I tend to go the 'alt' routes in upgrading my builds vs the common/simple way.

Not sure what measurements are needed, but, my frontend is at a rake of 55degrees w/ a 20"wheel. Currently, I have a 'drop' of the frame, when I turn, and was warned 'against' having one, so to correct it Im implementing a 'springer' frontend to it (plus the added weight couldnt hurt). I haven't 'measured' the trail/drop yet, but Im guesstimating a 4" trail and a 1" drop (just a guess, dont shoot the messenger, Im more than likly wrong ). Im also not sure the amount of trail I 'should' have to maintain a steady control at 30-40mph... and still have the ability to easily 'whip' the rear around... 'controllably'.

Another thing Im wondering, and I know it's good to have 'some' trail, but what occurs w/ the steering, at 0 trail setup? Is it sketchy?

So...

A-What is a 'good' trail to have for 30-40mph?
B-What happens to steering w/ a 0 trail amount?

Any assist/links in this would be grateful...

 

[itsid]

well, you can't have "no drop" with a single front wheel..
to do so you need the widest wheel (basically a ball)..

So let's forget about the drop for a second;
instead allow me to ask..

If you're happy with how the trike handles at the moment (it reads like you are)
Why do you want to mess with it's geometry at all?

if you flip the fork (pointing backwards)
install the rockers to the current axle mounts; you might be able to end up with about the same geometry in the end.

small adjustments can be made with the springs or slightly longer/shorter rockers..
but the trail and rake will be very close to what you have now.

which is likely a good idea


Now as a bonus round, back to the drop:
the smaller the steering angle and the smaller and wider the wheel the smaller the drop;
but if you're concerned, a 24" front wheel adds some additional room, and you don't have to be too concerned about the dropping at all
Or somewhere around the mid eighties there have been odd 22" bikes (BMX racers even)
If you can find one of those, you get the additional inch of clearance

'sid

 

[Bladerunner]

Gorgeous bike. Makes me wanna build one now. Putting pedals on the front wheel there would make it a legal motorized bike in CA. But then I start thinking I wanna do a bike with a sidecar so I can lug my dad around in it, cause he refuses to ride any of my creations.

Most people will tell you your trail needs to stay within the 2-5" area, but that is nonsense. As long as your trail is 0 or more, you'll be fine, depending on other factors.. On a trike this might not make a difference.. I don't know. I would talk to someone who knows fast trikes.

Be careful if you decide to go with 0 trail. Suspension compression will reduce your trail-assuming the action is parallel to the rake centerline.

Personally I would stay on the safe size and go with 2" or so.

Like itsid said, switching the forks around and adding links will work (to KEEP you current trail), but the reasoning behind it is inaccurate for this application. A standard fork for that size wheel assumes a much smaller (steeper) rake angle, and will have the right amount of trail to do so (around 2 inch). Put the same fork on your bike with higher rake will cause trail to increase greatly- like to five or six inches. Therefore you can use the stock locations to mount your springer links. An easy way to do this would be a simple 2nd fork in front of the fork in your headtube, that connects to the wheel axle along with two links machined or just hacksawed from some 1/4" steel plate. I would drill and ream the holes to press fit some bronze bushings. Don't know your setup, but you'd need a drill press with at least a half inch opening drill chuck to hold the drill to do this stuff.

So many choices. 2nd fork with spring on top, mini-shocks right near the wheel hub, reverse link and leaf spring, girder design, or regular telescoping shock design. There are others, too.

Depending on the angle between the suspension link and the rake angle, you can decide what the approximate line of action for your suspension movement will be.

I would also look into building a girder-style springer fork, similar to a Girvin or Noleen. This type of fork has one pivot above the headtube and one below, and the entire fork with wheel moves as one using hinging in two spots above and below the head tube, normally with a single spring between the links, in front of the headtube. Changing the length and starting position of the links allows you to manipulate how the trail changes as the suspension is compressed. There is a lot of info on the net about this stuff.. this post just scratches the surface of the info you'll find and problems you'll encounter.

Also.. stay away from the schwinn-type springers. They are very weak and will NOT stand up to the power of that 6.5hp.

 

[Half-breeder]

Well, Im not sure the 'design' I made... but it seems to work very well. TY for the info. Ive shortened the trail to 2.5" and .5" at FULL compression of the springs...

... and yes thats a horseshoe!

 

[Half-breeder]

... that's 2.5" w/ me on it... and I dont weight nowhere the amount to go full compression of the springs... it took 2 guys just to compress it fully... and IMO it had alil more to go.