Street Fox Mod Idea: Suspension?

I had a thought after seeing some bike builds on Youtube and was wondering if this
is possible. Getting rid of the cross boom section completely from the Street Fox.
Where the cross boom attaches, add two thick tab with holes for bolts.
Attached to those bolts, (and this is where I'm stuck) some sort of tubing with
shock springs to add suspension? I don't know if I'm describing what I'm seeing in my
head, but basically instead of the closed tubing, you have an open mount where the
spring is mounted at a 45° or so angle to add suspension.
 
Search youtube, and you find exactly what you see in your head.


I have to admit, watching it in slow motion and learning and understanding, I'm sure Brad
being the originator of the Street Fox, could incorporate this into the Street Fox coming up
with a totally new design called the Glide Fox :)
 
The bike paths around my area have lots of disjointed sections from frost heaves. I've managed to avoid pinching a tire or bending a rim so far, but I've wished for suspension on my trike.

Daydreaming while bouncing along, I've thought of the "Twin I Beam" front suspension on my old 1968 Ford pickup truck. It was basically a swing axle setup, except the axles were long and crossed over, with the pivot on one side near the wheel of the other. I drove that truck for ten years, and "it drives like a truck." Despite the (many) theoretical deficiencies in geometry, it didn't exhibit any bump steer, wheel tramp, or other undesirable behavior.

One nice thing about the Twin I Beam was that all the parts were big and simple. There was about 2/3 of a beam axle going crosswise, with the wheel on the outboard end. There was a radius rod anchored to the back, to locate the axle fore and aft. And that was it; no finicky precision joints or linkages.

If anyone is interested in such a thing, look at one of the old Ford truck web sites for information on the steering linkage geometry. It's simple and quite ingenious, and one of the reasons the trucks drove so well.


Something lighter, but more complicated, would be trailing links, like older VWs and Porsches. You could build a Twin-I-Beam arrangement easily enough with an angle grinder and a welder, but it would probably take some brainstorming to be able to do that for trailing links.
 
I think it would become quite complex to make work correctly. Imagine only one front wheel taking on a pothole. The stress would be delivered right to the suspension components at the crossbeam in a twisting motion. I think the only way a tad will have front suspension is with a very complex double wishbone system of some sort.

Might just be easier to add an air ride type suspension under the seat if you are looking for a super smooth ride.
 
Thank you for replying Brad.
Now that is something I hadn't considered. Still though, the video is fascinating to watch.
What do you think of the crossbeam under the main boom idea?
Also, what do you think of extending the tubing to the other side of the wheel and instead
of a hole for the hub tabs like on a bike fork? That would make the wheel more stable and
reduce stress on the axle itself. Being from NJ and mostly crazy, I tend to like to try new things.
While an air ride seat like they have in busses and 18 wheelers would make for a smooth ride,
my thought on that is it would make the Fox a lot heavier.
Have you seen trikes with that type of a seat, or do you know of an easy work-around?
 
The stress passed to the cross beam would still be less than hitting the same pothole with no shock absorbing suspension. The example above is similar to that used on some of the very expensive ICE trikes. It will work well but will be hard to make and therefore expensive.
00408-scaled.jpg

Ice turn this one 90 degrees so the wishbones become trailing arms.

Other ways of having front suspension are:-
A spring on the kingpin.
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Pros are it's easy and cheap. Cons are you need to have zero play in the kingpin or the wheel will wobble. Sliding kingpins went out of use on cars a century ago largely because of this. It has limited movement.

Double wishbones.
cafeab75014bbaf4d9480f4bed743c3d.jpg

Pros are it's a time proven system that will work. Cons are it's time consuming and expensive to make if paying someone. Note the steering arms are pivoted in alignment with the inner A arms pivots. This is essential to eliminate bump steer.

Composite spring leaf.
images

Pros are it will work and will be light. Cons are it is undamped though in reality that's not a major issue and getting the correct rate is not easy. It could get expensive depending on what you are paying for the composite.

There are others but they are usually not in use because they are poor or worse.

In every case you will need to limit front suspension movement to a small amount if you intend to corner fast. Fast cornering will throw the weight to the outside wheel and the trike will lean in the opposite way to the corner. If you intend to pootle about you can have more suspension movement. All suspension will add weight except perhaps the sprung leaf. Weight is simple to add and a bugger to pedal without assist.
 
Thank you for your expertise. I'm still learning about all of this.
The first picture looks like something professionally made.
I wonder if that is something that is sold as an individual part.

The second picture, I'm not sure what that is or how that works.
It looks like it might be a combination of a seat post and tubing?

The third picture looks like it would work quite well but I am not a fan
of under seat steering. For the StreetFox, it looks like the third picture
might work, but not sure if that could be redesigned for the direct
steering used by the StreetFox.

The composite spring leaf looks to be a bit thin but from what I've read,
it can be quite strong but can suffer from twisting while braking.
I did see a youtube video, i think it was the Azub Ti that had
something like that, but I think it was titanium.

Now I have to find someone here in Washington in the Seattle area
that does this kind of work.
 
The Azub methode on the TiFly is "simple" enough, But expensive in excution. Titanium plate-springs with shockabsorbers for dampening.

The setup on the HP Velotechnic Scorpion FS is way complicater. But as it uses cheaper materials and more common assembly technicques, it not a big difference in cost;
 
The part in the first picture is availiable to buy. I've seen seconds go on ebay direct from the maker. Presumably they also sell perfect ones. Under seat steering is vastly better than direct to kingpin steering. Having tried the latter it is just awful in comparison. Not a fact, just an opinion. USS or tank for me.
 
I have a KMX Typhoon trike with direct steering. I like almost everything about the trike, except the steering. I have long ape arms, and the steering arms force my elbows back almost to the back of the seat, which is uncomfortable. There's a bit of fore/aft adjustment on the arms, but the bike appears to have quite a lot of caster and is remarkably hard to steer already. Also, direct steering means that even small movements of the arms result in large directional changes.

I'm not sure I dislike it enough to do anything about it, and under-seat or tank steering would make it difficult to lift it into the back of my truck. I can grab the front and back of the seat, bend over, and heave it up as it is; that wouldn't work with a handlebar in the way.
 
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