After making the rear end, I found myself in a stage where I would be making too many estimates and guesses and I didn't want to mess anything up terminally, so I decided to go make a 3D version of it first.  Below is how I want it to end up.  The handlebars are subject to change as I don't know how they will interact with the tilt-steer and the seat clearance.  It'll have a 24" rear wheel with 20" fronts, and a slightly modified seat from the one shown.

     Below are two close-up views of the main pivot.  I set it up so the pivot would have an initial angle of 15º but it can be adjusted to anything I like if it doesn't work out.  It's made out of basic ½" bolts, ¼" steel flat bar and some nominal steel tubing.  Any alignment issues can be sorted out by shimming one side or the other of the main pivot housing and connections.  A note on the pivot angle though.  The angle I quoted is based on assuming that parallel to ground level is 0º, so the pivot is tilted up at the front to a 15º angle.

     To the right is an exploded view of the pivot and I'll explain the pieces.

1. Front pivot plates made out of ¼" x 1¼" flat steel, 2¾" long.  These are welded to the sides of the boom/backbone and extend downwards so the main pivot bolt can be bolted to them.  They secure the front end of the main pivot.
2. Rear pivot plates made out of ¼" x 1" flat steel, ~6" long (will be).  These are bolted to the boom/backbone at their tops, and to the main pivot bolt at their bottoms.  These secure the rear end of the pivot and allow for pivot angle adjustment.
3. Main pivot bolt.  The main pivot bolt is a Gr 5 NC ½" x 4" bolt with a piece of ¾" x .125" wall steel tube welded across the head of the bolt.  The crossmember pivots on the ½" pivot bolt, while a 3" long Gr 5 NC ½" bolt (#6) goes through the front plates, and secures the steel tube in place.
4. Pivot adjustment nut.  This is a ½" nut that has been drilled out to ½", and it has a ½" Dia steel tube, 1¾" long, welded across one of its flats.  The nut slips on the main pivot bolt, at the back of the pivot, and is held in place by the main pivot bolt's nyloc nut (#8).  The adjustment nut secures the rear end of the pivot bolt and also allows the rear end of the pivot to raise or lower to adjust the pivot angle.
5. Pivot housing.  This is the same steel I use for the trike king pin housings.  2¼" long, 1" OD x ¾" ID steel tube with two HMDP flanged bushings in either end.  This housing is welded in the center, on the top, of the crossmember and allows the crossmember to pivot in relation to the backbone/boom of the trike.
6. Front pivot bolt.  This is a 3" long Gr 5 NC ½" bolt that secures the front end of the main pivot bolt by pinching it between the front pivot plates.
7. Rear pivot bolts.  These are Gr 5 NC 5/16" x 3" bolts.  The top one secures the top of the rear pivot plates (#2) to the backbone, while the lower one secures the pivot adjustment nut (#4) by pinching it in between the bottoms of the rear pivot plates.  The bottom bolt can be removed and put in any one of a number of holes in the plates to adjust the pivot angle.
8. Main pivot nut.  A ½" Nyloc nut that tightens up the whole pivot assembly and keeps the pivot adjustment nut in place.

     Clear as mud?  Excellent! :)  A little more complicated than I would have liked, but I need to make it adjustable so I can figure out what the optimum pivot angles are.  Once I find that out, I can weld the rear pivot plates to the trike frame too.  So, on to the real McCoy.

7 Jan 2007

     For the last two days I've been banging away on the trike frame.  The nice thing is/was that I got to break in the BB and frame jigs really well, and I am extremely happy with how well they worked.  Alignment was within 1/64" or dead on, and all the clamping and bracing I had to do before is now a thing of the past.  W00t!

     So, the frame went together as per the 3D plans but I was a little concerned about the BB to crossmember distance.  In my mind I could visualize how the steering would work but wasn't completely sure on what that would do to heel clearance of the crossbar when turning.  After a little clamping and testing I discovered 2 things . . .

1. Thankfully, as you turn, one crossmember side moves back and up, while the other side moves forward and down.  That means that heel clearance is not an issue, but the front wheels could hit the side of the seat or the side of your foot in a hard turn.  And . . .
2. The 15º angle I initially planned for is perfect if you have about 40 acres to turn around in but pretty much useless for anything but straight line riding.  With a little testing and temporary shimming (in the top picture), it turns out the "starting" angle is about 45º instead.  No problem though, as I cleverly anticipated some angle experimentation and if need be I can go to 90º or past :)

     With a piece of steel holding the pivot at the appropriate angle, you can see how much the rear section tilts and how much steering input is produced as a result.  I'm pretty happy with the steering deflection, but at the current 45º pivot angle, I need to see what kind of seat clearance I have.  Because the crossmember turns itself out of the way of your heels, the BB to crossmember distance has ended up being shortened to about 16" from the original 17½".  This also means that the wheels are further forward and less likely to come in contact with the seat with shorter riders.  When I made the crossmember, the total width should be around the 31" mark because I still wanted it to easily go through doors.  What I didn't think about was the fact that the crossmember can tilt and the total width would be less than 2 feet - which is no problem to wheel through a doorway.  What I could have done, was add maybe a couple inches to each side which would mean even less chance of the wheels hitting somthing while turning, it would make the track 4" wider which would enhance stability, and it would still easily go through a doorway.  I'm not too concerned about it now and I can see what is what when I get the chain on it and try a test ride.  Next thing is to fabricate the last few pivot parts and make a seat frame so I can start seeing what kind of cockpit issues arise.

8 Jan 2007

     The pivot was finished and mounted up using my mock-up AL bushings.  Alignment seems good and everything is fairly tight, but there is a little play in the mock-up bushings but I can still shim the plates a little left or right to trim out the trike so it goes straight when the frame is level.  No problem there.  I drilled 6 holes in each adjustment plate at 3/8" intervals to fine-tune the pivot angle.  If need be, there's lots of room for more holes.  Once I find out how the trike handles for the angle adjustments, I need to see if I can come up with some kind of omni tilt-stop so the adjustment plates don't hit the crossmember at full tilt and/or to stop the tires from hitting the seat.

     As the angle approaches 90º, it requires less tilt to produce more steering input, but the tilt gets "heavier" - same as wheel flop.  Reducing the angle also reduces the steering weight and reduces the amount you can turn.  What I want to find is the happy medium where you still feel a little lateral force pushing you to the outside on a turn, not down into the seat.  How comfortable the tilting and steering will feel depends on the combination of how fast you are going and how tight you need to turn.  I want to do some ice racing with this trike, so I imagine there will be one setting for the slalom and one for the pursuit/lap races.  The slalom requires tight, quick turning while the pursuit/lap racing requires less turning radius and longer, faster turns.  I'll make the skate blade adapters after the trike is finished.  I'm forming a rough idea of how to make a small linkage that will allow you to switch between a "high speed" pivot angle (ie less than 30º) and a "low speed" angle (ie above 50º) while riding, but for this one, I don't want to get too fancy and cluttered.  I'll figure things out first, then maybe try it on another tilt trike if I like the way this handles.  It certainly is easier to build than a conventionally steered tadpole and you might even be able to ride it no-hands - for whatever bonus that actually makes.

     The bottom picture is the frame with the cranks mounted and the seat frame temporarily clamped in place.  The seat frame is a little flatter than my previous ones and the strategy behind the whole trike is this:

• make the trike as low as possible for good stability, but not so low to cause ground clearance issues or to hit the ground with the seat frame on turns
• use a 24" rear wheel so I still have an acceptable high gear, but a slightly shorter O/A length, and the smaller diameter means the seat can be tilted back further and still clear the rear wheel without having to add extra length to the center frame section, and lastly
• lay the seat back more, somewhere near 30º, so it has a lower CoG and a better aero profile.  The seat base-to-back angle of 60º has been flattened out to 45º so the seat rails don't dig into my hamstrings when the seat is leaned back and the 30º kicked-up tops of the seat frame will help hold the shoulders in place.  If need be, I can make another headrest for it.

     While this trike isn't initially set up to be a great hill-climber due to the laid seat, the seat can be raised to a more conventional angle if needed.  I haven't decided whether I'll use a single seat support or two supports like the ones I modelled.  Next thing is to finish up the seat mounts, put the mesh on, shift the 20" wheel axles over to one side, put some tires on them, and run the chain.  After that, I should know what I need to about what pivot angle is optimum and where I might have problems with the front wheels hitting.  I'll also be able to see what I need to do with regards to the handlebars.  I need to keep busy because the ice races are the first weekend of Feb :)

10 Jan 2007

     Over the last two evenings, I finished up fabricating all the seat tabs and the rear seat support complete with QR.  I sat on it and I like the angle but I think the seat can go forward one more hole and the seat tilted back a little bit more, just for testing.  It would have been nice to have the pivot above the CoG so the trike would be self-righting, but I'm happy with it so far.  I made a little jig to help speed up the process of drilling the seat holes and making them more precise and better aligned.  It will appear in the jig section soon.  Next on the list is to weld on the RD tab, run the chainline and mount the chain pulley.  After that, I need to add a few more tabs and brackets at the rear of the chainstays, mount the tires and address the handlebars.  I'm getting some parts in on Friday to complete the project so I should be pretty much test-drive ready for the weekend.

12 Jan 2007

     Two more evenings worth of work on the trike.  Chainline is run with a single pulley (roller blade wheel) and ~2.6 lengths of KMC Z-51 chain.  I mounted a 42/34/24 triple with 152mm cranks and Wellgo SPD/platform pedals.  The axles finally got shifted over and the tires mounted with Kenda Kontacts.  I also have both steering arms made but not welded on yet as I'm finishing up the handlebar and brake mounts.  I also managed to get out for a quick test ride too and I really like the ride.  It was weird with the tilt steer.  From riding normal tadpoles so long, I automatically tried to resist the tendency to tilt or tip, but that was obviously counter-productive to steering.  Once I relaxed a bit, it handled smoothly and bump steer was a minor annoyance at best.  I adjusted the pivot angle up to around 55º before going out, but I'll measure the actual setting once the handlebars are on with the shifters and brakes.  I need to give it a half decent run so I can figure out what the steering is doing and how much body lean is required.  So far, the steering feel is very light and nowhere near as heavy as I thought it would be.  I was thinking I'd maybe make the next one (if there is a next one) with a 2" or 3" wider track to aid cornering, so I experimented with turning the wheels as far as possible and seeing how wide it was and whether that would help going through a door.  Right now the trike is around 31" wide.  With the wheels turned, it's up to 4" wider, so a wider trike would have to be tilted on it's side a little to go through the door.  If all goes well, it should be done by Sunday or Monday and I can send it off to be powder coated.

15 Jan 2007

     For two of the last three days I got some good effort on the trike, but it doesn't really look it unfortunately.  On any bent, after the main frame is done, progress really slows down as the finer details are handled with not much being readily available.  The bars are on and they feel pretty good, but they might get in the way, so I'll tilt them out a few degrees and see how that feels.  The brakes and handlebar clamps mounted up nice and more easily than I anticipated, so that's good.  Now, all that really needs to be dealt with are mounting 3 or 4 cable stops, 6 tabs and give it a good test drive.  I might need to take it to work and give it a good turn around the hangar because I don't really want to take it out in the snow (yeah, we finally got some snow :( ) and get it all rusted up with it so close to being done.

     The pivot is set at 60º right now and it feels pretty good and doesn't feel top heavy at all, mind you all that could change when I try to ride it.  The long rage forecast doesn't look like it'll give me a test ride opportunity, but we'll see.  I have 3 weeks to finish it up yet, but I still have one more project to get online before then as well.  So, I'll tweak the handlebars and do up the tabs tomorrow and maybe even get the cable stops brazed on. After that, the only thing is making a temporary rim brake adapter for the rear wheel to be in compliance with the ice racing rules of dual brakes.  I plan to have skate blades on the front - so not much braking action there :)

21 Jan 2007

     I've been working at it pretty steady since the last update.  Unfortunately, now is the time that little progress is apparent for the time spent.  However, I did get some important things done.  I got the handlebars tweaked, mounted the flag tube and got all the tabs mounted on the back end.  I also got all the cable stops mounted - and that's strike 2 for brazing attempts, so I welded them on again.  I fabricated a dual rear brake adapter that sits over the rear wheel and mounts to the tabs I just added.  I had to do this because the ice racer needs to have two independant braking systems and I lost both of them when I put the blades on the front end.  The brakes are just two old side pulls that I modified to mount back-to-back, and I switched them for bottom pull too.

     I also got the blade adpaters/holders fabricated using kids' skates that I chopped up.  I bought a 4' length of 14mm threaded rod and made the rest out of 1" and ¾" box tube and some pieces of ¼" plate, and made them so the front end was dropped about an inch.  I sharpened the blades to about a 60º point and the running surface is about 4" long.  On the Sabre, the running surface is much longer and it makes it a little twitchy in the corners.  I drilled everything in pairs so the two sides would be as symmetrical as possible and once everything was mounted up, the blades were within .032" on parallel - a very acceptable level of accuracy for my efforts :)

     After getting everything tightened up and mounting a 24" Maxxis Holy Roller that I spiked up for last year, I put the Delrin pivot bushings in and took it to a local outdoor rink.  It still feels weird that I have to tilt to lean and I find myself trying to fight the tilt.  Once I relaxed a little and got a few laps in, I was really please with the way it performs.  The steering wasn't twitchy at all, there was no pedal steer and I had no problem turning as sharp as I wanted.  In fact, I'm going to reduce the steering ratio a bit and make it lean a little more on the corners.  It has a slight tendency to drift left but not enough to be annoying.  It's either because the crossmember end heights are not exactly the same, or there is a small welding misalignment in the pivot area.  Afterwards, I also noticed that in my haste to put the rear wheel on, I didn't get it straight in the dropouts.  After everything is painted and powdered, I can adjust out the problem by shimming the rear pivot plates (as designed) or I might even be able to do it with slight adjustment of the rear wheel.  I'll have to see.

     Overall, I'm extremely happy about the way it handles and the blade adapters didn't look to be flexing in the slightest.  By my way way of thinking, if I could pull 2G's on a turn, which isn't possible, that would make the side loading about 400lbs.  I don't think there's any part of the adapters that couldn't take that and any flexing or vibrating would have produced chattering on the corners - but there was none.  The outside blade seemed to be understeering a bit which might be because the running surface is only 4" long.  I'll grind it flat to 5" and regrind the edge, and then test it again and see if that helps.  I also want to add a few more rows of screws to the rear tire.  If I remember correctly, I was able to spin the rear tire last year with the amount of screws that are in it now plus I was cornering flat, so I want to add at least one more row of screws up towards the sidewall.  I have almost two weeks to get the final bugs out, so I'm not too worried.  In the eman time, it's been disassembled and will be dropped off for paint and powder tomorrow.  Hopefully it'll be back by mid-week.

07 Feb 2007

     The ice races have come and gone and I managed to get the trike finished and turned into an ice racer.  I experimented with the pivot angle and settled on about 60º and it worked very well.  The only real problem I had was not enough traction with the rear wheel, and there is a slight tendency for the trike to want to drift to the left  More ice races are coming up, so I'll just put more screws in the tire, and shim the pivot plates with a washer to correct the tilt issue.  The trike was very easy to handle at low and high speeds.  To turn, you just do it a little more aggressively than a normal trike and there was no problem.  It was very smooth in the corners and very easy to handle.  I'm not completely happy with the handlebar position, but I needed a neutral position until I finalized the angle, but they still work fine.

     For ice racing, I took off the front wheel brake calipers and made a removable dual brake frame for the rear wheel plus a fender to keep the ice spray off my neck while racing.  I also installed a Maxxis Holy Roller 24" knobby with a few hundred screws in it that are off-set to the left side of the tread.  That is because the fast racing is predominantly counter clockwise and that's where I need the traction.  I am very happy with it's performance and it only wanted to tip when I was steering into a power slide.  Tilt steer trikes need to be re-assessed because they are much more comfortable to ride thatn I have heard/read and they are certainly much simpler to build.  The only thing to decide is the final angle for the pivot.  I don't know how it will handle on roads with bumps, etc until I'm done ice racing with it.  So for now, I'll put some more screws in the rear and get ready for the Toronto Courier ice races on Feb 24th.

27 Feb 2007

     Well, I took it down to the ice races, but it didn't do as well as I would have liked, but mainly due to my mistake, not a problem with the trike.  I added about 150 more screws to the rear tire, but mainly on the left side to help in cornering. I adjusted the tilt angle so it would lean more in the corners and bite harder, but I didn't adjust it enough, so it still ran too much in the upright position. It wasn't leaning far enough to really bite hard with the news screws. As a result, I was still sliding through the corners and scrubbing a lot of speed, so it wasn't fast enough to make it into the semi's or the finals. Oh well, maybe next year, but now, it's time to convert it back to a trike and see how she handles.

11 Mar 2007

     I removed all the ice racing paraphenalia and reinstalled the front wheels and brake calipers. The process went rather quickly and I managed to get it out for some short test rides in the nice sunny weather we had.  The trike is very smooth and very responsive. The initial problems I had with tilt-steering are gone. It's almost like you "think" about changing directions, and it happens. I was concerned about rough ground, bumps, road camber, etc. None of it caused any problems at all. Right now it is set up to produce a lot of steering input for minimum tilt, so that likely adds to the stability.  It has a very comfortable turning circle for the 58º pivot angle it's set at right now and a minor pull to the left was rectified with one thin washer. The only thing I noticed was a slight side to side motion like pedal steer, but it is not a weight or balance issue, but a matter of my sloppy pedalling technique. I guess on a tilt steer you need to be smoother still in your pedalling technique, but it wasn't annoying, the trike was still plenty fast and felt rock solid.

     The only thing I'd change, is maybe make the crossmember a couple or three inches wider, and lower the handlebars and bring them in a little.