Home Built Bikes
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Prototype Tiller Steer/Braking Tiller steering/braking I saw a few other tiller type steering set-ups on other trikes while cruising the web, but couldn't get a clear idea of how they were built. I decided to try my own design and add braking to the handles as well so the only cables coming off by the hand grips are the ones for the gear changers. I also figured they would look pretty cool :) It's a little more complicated than the direct steering that I've been using so far, and it uses more tie rod ends as well (6 instead of 2). The tie rod ends I have access too have a little slop in them but it's manageable when only used to connect the front wheels. I'm concerned the sum of the play in the three steering rods and their tie rod ends might prove to be too much. I'll have to build one and see I guess. I just modelled the single side for the time being and will put it on a trike mock up when I get the rest of my "bright ideas" out of my head. An animation (~1.5MB) is at the bottom.
This is a model of the left hand tiller. The steering rod on the right would connect the tiller bar on the right hand side of the trike to keep them synchronized. The left steering rod would connect to the right front wheel and actually turn the wheel left and right. The 1" square tube running to the rear of the picture would connect the tiller to the trike frame under the seat. The brake cable is seen sticking out the front of the tiller and would run to the left front brake caliper. To steer, you just push left or right, like an aircraft control stick.
In this picture, the handle is pushed forward to apply the brakes. Pushing forward on the handle at the top, causes the bottom to swing out which pulls on the brake cable and applies the brake. I decided to push-to-brake instead of pull because I often pull pretty hard for extra leverage on the handles when I'm really grinding hard. The brakes can be applied together or individually, whether the wheels are turned or straight. The pivots are 1/4" grade 5 bolts and turn inside oiled stainless steel tube pieces.
Tiller bar pulled right, to steer right.
Tiller bar pushed left, to steer left. Brake is being applied at the same time.
Front view showing brake cable housing, pivots and tie rod ends. Animation (~1.5 mb) |
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I want to go riding with my lovely wife, but I like riding hard, while she doesn't and I need to spin (because of my knees), while she is a grinder. A solution to the first part of the problem is to build a tandem, either trike, 2 wheeler (or both :)), that way we can ride together regardless of fitness level or riding speed. The second problem needs to be addressed in a different way. The solution to the second problem is independent drive systems for the captain and the stoker. I've seen a few ideas/versions on the net, but they looked pretty complicated and/or usually required some kind of custom machining and/or parts. I didn't want to have custom parts, nor did I want to have to rely on access to a machine shop, or expensive milling, for repairs. I think I've come up with an independent drive that:
So, the independent drive consists of:
On to the parts. First, we take the aluminum discs and attach them to the small chainrings. I modelled these using 28 tooth granny rings from a mountain bike. The aluminum adapter discs can be made with nothing more complicated than a jig saw or band saw, a hand drill and a hole saw. In fact, the "discs" don't even really have to be round if you don't want to - they will work fine if they are square too.
The aluminum discs are used as adapters to attach the chain rings to the hub flanges in the tandem's mid-drive. The chainring can be attached to the aluminum disc however you like, using rivets, nuts and bolts, or chain ring bolts. The aluminum adapter would have a hole in the center of it that is big enough to allow it to slide over the end of the axle and hub, and sit flush against the face on the outside of the hub's spoke flange. In this case, I was planning to use 2024/2117 3/32" universal head rivets in the spoke holes to rivet the aluminum disc to the hub flange. I coloured the granny rings black to make it easier to see them in contrast to the chrome coloured cassettes. Another option, is to make your own chain rings using the templates supplied here, and again, nothing more than basic hand tools is required and you can make the adapter disc and chain ring all one piece.
The captain's hub is pictured above. The aluminum adapter disc and chainring have been rivetted on the outside of the hub flange, on the non-drive side of the hub. You can see the rivet stems sticking out past the inside face of the flange. It would likely be easier to reverse the rivets and put the manufactured head on the inside and the shop head on the outside. The new granny gear will carry drive from the captain's hub, back to the non-driven side of the stoker's hub. The stoker's hub is pictured below.
The only difference between the stoker and captain hubs is that the stoker hub has the adapter disc and chain ring on both spoke flanges, not just the left one. Obviously, to get the extra chain ring on the cassette side, you need to remove the cogs, install the adapter disc, and then put the cogs back on. The adapter disc on the left spoke flange connects the stoker's hub to the captain's hub using a short piece of chain. The extra chain ring on the cluster side connects the hub to the rear wheel and transfers the drive power from the riders, to the rear wheel via a single chain. Below, is a picture of the full drive, with the chains numbered to indicate what their job is. I didn't add the chain coming from the bottom of the clusters and going through the derailleur cage because my computer was going into vapour lock just trying to render what is already there. :)
The chain numbering:
The benefits so far are as follows:
Below is a left side view of the mid-drive system, with the gearing numbered.
Below, are close-up pictures of the captain's and stoker's hub.
The two mid-drive hubs are modelled with 3/16" x 1" x 4½" drop outs, but I would likely build some kind of more robust mount for them using 3/4" x .049" steel box tube. This design, I think, would work on a large number of chain line layouts and with almost any combination of hubs. At the very least it would work with a 24, 24 and 8 speed gearing combination for a 20" BMX wheel with 48 spokes. My only concern would be if the rivets start to loosen due to the load from driving the extra weight of a tandem off on only one flange at a time. With some of the higher flanged, inexpensive hubs out there like the M475, I could even oversize the spoke holes a little and use small bolts with lock nuts. Update: A suggestion from an individual on the trikes mailing list was that instead of using two hubs in the "mid drive", simply use a disc brake hub on the rear wheel, and run chain #2 all the way to the rear wheel, which has a chain ring attached to the hub's disc brake mount. This would remove the need for the stoker's hub altogether and the stoker could drive the rear wheel directly. A very good suggestion, I think, because the suggestion reduces the complexity, the cost, and the weight. Additionally, if I use a disc hub for the captain's "mid drive" I can fasten the chain ring to the disc mount on it as well, and remove the need for all the rivetting. While I lose the ability of using disc brakes on the rear (which was one of the features I wanted), I can still mount discs on the front if I want, along with a good rim brake for the rear. Real pictures will come when I get the tandem under way :) |
