Take a Seat!

Our next round of modifications focused on making the trike more ride-able and more suitable for commuting during busy times.  While everyone had started getting used to sitting on the folded up towels stuffed into a bag, I figured that it was definitely time to get a real seat.  I picked up a lightweight, little kid seat when I was back home over break, and it fit pretty nicely for the purpose.  The blue seat also managed to keep our blue/white color scheme in order:

 I wanted to bolt the seat down to the frame, as opposed to welding it directly, so that it could be easily removed when necessary.  I cut the front legs completely off with the angle grinder, but left a little bit of the rear legs sticking down for mounting to the trike.  I welded a short piece of angle iron to the bottom of the legs that stuck off backward, under the rear trike square tube (below).  I had tried to cut the legs at a slight angle such that the mounting fixture would give the seat a slight lean backward.  After welding the angle iron in place, it was easy to drill holes and bolt the component of the seats directly to the trike frame on each side of the seat:

Rear Leg Mounts

The bottom of the seat rested nicely on top of the chain stays from the trike frame, and a final, third bolt secured the seat at that point.  I welded a short piece of angle iron to the trike frame, so that we could drill directly through the tube that comprised the legs, and then bolt the angle iron to the base of the chair at that point:

The three bolt mounting points held the chair down directly to the rear of the trike.  Although the front of the seat is cantilevered out over the center of the vehicle, it wasn't a problem as most of the rider's weight is in the back of the trike, where the seat is bolted down. 

It held together perfectly fine, and definitely achieves the goal of making the trike much more comfortable than our original, makeshift seat...

Safety First!

At this point, we also had concerns regarding how practically the trike could navigate the bike path and sidewalks when there were other people around.  It was a fun drifting machine, but at the same time, the rear casters made it very unpredictable.  While we could eventually reach a decently proficient point of adapting to the drifting steering dynamics, it was still very uncontrollable in the case of sudden swerving for obstacle avoidance.  

At the same time, I experienced the problem of fluttering in the caster wheels.  Driving down long, straight sections of road, I could only reach a certain speed before the rear wheels would shake to the point of rapidly swinging side to side and clapping loudly, dragging the trike back down to crawling pace.  Though it typically didn't occur at short distances, you can hear the sound of them shaking like a tambourine right as I hit the trash can in this video of me driving down the hallway:

It was interesting that this occurred when the trike was going directly straight, so I originally thought it could be a fault in the wheels.  They had a slight rattle as they spun on their bearings, and it seemed almost like they hit a certain speed and the wobble reached a point of harmonic oscillation of sorts with the whole caster.  I tried just pinching the wheel tighter with washers as spacers, to hopefully restrict the wheel and limit the rattling.

The wheels spun a bit more smoothly, but still fluttered a bunch when I hit high enough speeds.  After a little bit of research, I found out that this fluttering effect is actually a property and fairly common problem with caster wheels.  

Interesting article: http://blog.learning-2-live.com/causes-and-corrections-of-caster-flutter/

I figured that the solution to both increase our top speed as well as add control would be something to restrict the castering effect of the rear wheels.  I threw together a quick design using angle iron as a horseshoe type gate that would swing down and hug the sides of the wheel bracket when it's going straight.  Since the fluttering problem only occurred when we're driving straight, the idea was that the casters would do a decent job of straightening themselves.  On top of that, the horseshoes have a slanted, flange piece that funnels the wheel bracket and adds to the tolerance of positions that will allow the gate to drop down.  To start with, we just put a bungee cord on it to pull it back up when drifting.  

The first test run was very successful.  The gate flopped down much more easily than we had anticipated, and did a good job of restricting the wheel, although it was a pain putting the prototype on the side of the trike with the throttle hand, which made it difficult to slam the piece into place over the wheel while driving.  Even with the design just on one side, it still did a good job of limiting the flutter.  We put one on the other side the next day:

With the gates on both sides, it made the trike able to go much faster, and added a great deal of maneuverability.  Now having essentially no castering effect, it could handle and steer pretty much just like a standard, ordinary tricycle.  We connected the two by welding up some white, steel tube:

In the spirit of recycling trash, this white tube was actually an old component of the support frame for a Walmart pool that we used to have in my backyard at home.  It's always nice when you can get random junk to work for your application. 

Anyway, the linkage turned out alright, and did the trick.  We mounted a handle on the left side to flop down both gates at the same time.  It's fun to drive, and the feel of picking up speed and then slamming down the gates over the wheels is almost like a throwback to driving stick back home.  I'm still working out the kinks, but it's been coming along.  I'm going to work on putting together another video of the new rear assembly soon.