5 Boro Bike Tour Tandem Trike: Spring Has Sprung…Kinda.
It looks like that last hurrah of Winter was a bit of a fake-out. As you can see from the photo, this was the state of my workshop on the first full day of spring. Yes, the equinox brought a snowstorm that straddled the end of Winter and the beginning of Spring.
I knew that I’d have to deal with clearing the snow before getting started. Unfortunately I also had a few other things to take care of before I could work on the trike. As a result, I got a late start. The good news is that it was sunny and warm so most of the snow melted out back by the time I was ready to go to work.
The main task for the weekend was to get the back wheel aligned and the rear forks onto the frame. As I read through the plans I noted that the truss tube was slated to go on after the fork legs. I felt that measuring and marking the truss tube would be easier before the fork legs went on. This would be the last opportunity I would have to lay the frame flat on its side Doing this would make it easy to mark the angles to cut the truss tube.
Remember that tip about ordering steel in lengths of 60 inches or less for the best shipping price? So far that has worked out well..until now. The 1 inch square tube for the the truss needs to be 63 inches and my longest length is 60 inches. Now I could weld another 3 inches of tube onto the end of the one I have, but I think that it’s better that the tube is one piece. As it happens, the home improvement stores stock 16 gauge 1 inch square steel tube in 6 ft lengths, so I picked one up. Yes, it was an extra expense but worth it. I’ll always be able to use the other tube on another project.
Measuring, marking and cutting the truss tube and the upright all went to plan. Where things went a bit awry was in capping the truss tube. Again, heat was the issue. I burned through pretty good and left myself a big gap to fix. By the time I was done patching and filling there wasn’t enough time to get to the rear wheel. I knew that task was going to require lots of patience and precision. There was no sense in starting if I was going to have to abandon halfway through the task. It would have to wait until the next day.
The next day came and so began the fitting of the rear wheel and forks. The steps are simple; Prop up the frame so that it sits at the correct ride height. Attach the fork arms to the rear wheel and align the center of the wheel with the center of the frame. Align the fork arms with the frame, keeping the rear wheel centered, and tack the arms in place. Easy.
It might be that easy if you have more arms than the typical human. If not, you’ll need helpers in one form or another.
Setting up the frame on the buckets was simple enough. I pulled out my level and was astonished to find that my workbench at the bottom of the stairs wasn’t just close to the same level as the porch deck, the bubble showed it was dead level with the deck. That meant I didn’t have to do all kinds of compensation for the frame height. As the saying goes, sometimes it’s better to be lucky than rich.
As the frame sat on the buckets I knew it would be level, but because of the welds on the very bottom of the frame, it didn’t sit exactly plumb. I adjusted my supports until my smaller level’s bubble was between the lines. OK, frame propped up at the correct ride height – Check! Oh, and BTW, being that the rear wheel has the fat tire, the diameter is a little larger than a normal sized tire. Your typical BMX wheel and tire will be 20 inches in diameter. The fat tire made that 22 inches. Normally the axle would sit at 10 inches but in the back it would sit at 11 inches. Not a big deal. The front wheels with their tires will be closer to 21 inches in diameter anyway so we’re really talking about a half an inch height difference from the front of the trike to back.
This next part is where it would help to have a few extra hands. Although born and raised in New Jersey’s urban environs, the toxins have not resulted in my acquiring such a useful, if not disturbing, mutation. As a result I’ve had to improvise. I told you about the magnets. They are always useful for holding steel tube in place. For the wheel I needed a stand of some kind that would keep the wheel plumb.
Using 1/2″ PVC pipe and some elbow and tee fittings, I put together a wheel stand. I didn’t glue the parts so I can reuse the PVC pipe in another project when I’m done. By strapping a bungee cord around the wheel everything stays in place but remains flexible enough for adjustments. With my bubble level against the sprocket, I got the wheel plumb inside the stand. Then I moved the whole unit to align it with the centerline of the frame. Starting in close, I moved it away from the frame until the fork arms made the correct angle with the stoker seat boom.
After that I made small adjustments, making sure the wheel was perfectly aligned on the centerline of the frame and remained perfectly plumb according to my level. With the magnets holding the arms and the wheel centered and plumb I could mark the spacers for cutting.
There’s nothing in the plans about how to accommodate a wide tire. I purposely cut the fork legs long because I knew I needed some extra leeway. To keep the tire from rubbing on the fork legs, I created spacers out of some 1.5 inch tube. What I needed to do was cut the correct angle on the spacer tube and tack those tubes to the frame.
The magnets helped again. They held the tubes in place while I marked them for cutting. Whet I found in doing that was that the hub is slightly offset, meaning that the spacers would not be symmetrical. The left side has a slightly bigger gap. This makes sense since the sprocket is is on that side.
Oh, in case you’re wondering, Yes, I have the sprocket on the correct side. The trike’s final drive will be on the left and all of the power transfer from the cranks will be on the right. This will let me use ordinary cranksets and allow for fully independent pedaling instead of the semi-independent pedaling system in the plans. How? You’ll have to wait a bit to see that. It’s another deviation from the plans but like the moped wheel and tire, I think it is an improvement on the original design. But I don’t want to jump too far ahead. We still have to get this wheel on the frame.
I marked and cut the spacers and got them tacked into place. Yes, they welds are ugly. Those aren’t supposed to be final welds but just meant to hold things in place. Once again I did the dance with the wheel and fork legs, double checking the wheel for plumb and centering after each adjustment. When I was satisfied I covered the wheel and tire with a fireproof fiberglass cloth and set to tacking the right fork leg.
Once done I went through the same process to get the left leg set for tacking. Once everything was aligned, I covered the wheel and went for it.
After the previous day’s ordeal with burning through the tube I was super conservative with the application of heat. I’m not all that concerned with the look of these welds since everything will be re-welded and reinforced with gussets. No one will ever see the tack welds…well except you but you know what I mean. Now the wheel can support the frame in perfect alignment. It looks right from every angle and represents hours of work. I just have to lock it in with the side braces, gussets and final welds. Then I can turn my attention to the front end.