HammerHead Trike - Page 4 of 7


Figure 9

If you look ahead at the pictures in this tutorial, you will see that both front forks are connected to the rod ends that are in turn connected to the control rods and then to the main steering tube, so when you turn the handlebars both wheels turn. The 2 control arms that are welded to each of the outer front forks are installed at a slight angle as to allow the wheels to turn at a different rate depending on direction. This is called "Ackerman steering", and it makes one side turn at a different rate than the other. You may wonder why you would want this. Let me explain.

Let's assume that you are driving around in a circle, turning to the right. The wheel on the right side (inside) is actually traveling less distance than the one on the left (outside) since the inner circle has a lesser circumference. Because the inside wheel is traveling less distance in a smaller circle, it has to make a sharper corner, so it needs to turn more to the right than the outer wheel. If both wheels turned at the same rate, one tire would have to drag in a turn, and this would slow you down and cause one wheel to skid.

Making the inside wheel turn at a sharper angle is accomplished by setting the control arms that hold the rod ends to the forks on an inward angle. To determine this angle, you just draw a line from the center of the rear wheel straight through the center of each head tube, as shown in this photo, and you get a fairly good Ackerman steering angle. If you really want to get into depth on the Ackerman steering concept, then search for "Ackerman steering" on the Internet and you will be able to read pages of information on the subject. If you just want to get up and running, use the method shown here to set your angles.

Figure 10

Cut and drill the parts shown in the following drawing from some 1/8 thick or similar thickness steel plate or flat bar using the measurements shown in this photo. The rounded area ground out of the top of each of the smaller control arms is a fish-mouth that will conform to the round crown area on each outer fork. If your forks have a flat crown area then you do not need to make this rounded area.

Figure 11

Once you have the three control arms cut, weld the larger one (the one with two holes) to the bottom of the crown on the center fork as shown in the next photo.

Once the main control arm has been welded to the fork crown, install all of the bearing hardware for the center head tube. Also, connect one rod end to the end of each rod and then bolt them to the control arm. If your rod ends do not thread into the rod, or you choose to use salvaged bicycle tubes like I did, you will have to weld the rod ends to the end of the tube. Only secure or weld one rod end to the control rods at this point, since you need to figure out the optimal length for the control rods by trial and error.

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You can build it yourself from our easy to follow DIY plans!