by Brandon Oberlin
This cruise control was inspired by the famous DK Whisper cruise control, which had the unique feature of “clicking off” as soon as the throttle was engaged. This feature offers two distinct advantages:
1) It is safer to use than a cruise control that requires the other hand to disengage; this one clicks off quickly and with one hand.
2) It is easier to use, as it can be engaged with only the pinky of the throttle hand.
The exact dimensions of this design will vary according to what type of throttle you have. The throttle handle that I use is a factory bicycle brake (TRP brand, with a sealed bearing) and a homemade throttle
body / kill switch assembly made from 3/4” and 7/7" Aluminum tubing.
The key part of this design is the saw blade, which has teeth that are oriented AWAY from the handle. A “Sawzall” blade served this purpose, as it is very hard steel, it is thin, and the teeth are small, but not too small.
A small homemade spring (made by bending music wire, available at any hardware store) keeps the sawblade from engaging, and needs to have enough tension to prevent it from accidentally catching.
The thin steel plate is made from a piece of the same sawblade (as it is hard steel) and it is sharpened on the edge that contacts the sawblade to provide solid engagement.
My TRP brake handle is partly hollowed-out, so that allowed space to run a 4/40 screw through it, which is the pivot point.
There are small pieces of aluminum tubing on either side of the sawblade (inside the handle, not pictured) that serve as spacers to keep the sawblade centered.
Additionally, the music wire spring is also mounted on that screw.
The screw slides freely through one side of the brake handle, and threads into a tapped hole on the other side. I used short 4/40 screws to hold the metal plate onto the handle,
but you could rivet this just as well. I painted the sawblade and metal plate portions with black spray paint for appearances. All screws are Locktited, of course.
One tricky issue to consider is making sure the sawblade is trapped by the handle when at idle, i.e. it is NOT able to come out and cause a jamming problem.
The other side of that same problem is that if it long enough to stay trapped when the throttle is at idle, it may be so long that it protrudes out the back of the body when the throttle is fully engaged.
I addressed this issue by adding the extra piece of tubing, which is simply there to add width to the handle to that the sawblade doesn't protrude out the back when it is fully engaged.
Again, the specific dimensions will vary according to what kind of brake handle and throttle body you have, but you should be able to use the sawblade principle to create a durable and reliable DK-style cruise control.
The cruise control is engaged with the pinky finger (in this case) and the finger just slides down between the lever and the handle, and pushes the sawblade down to engage it with the thin steel plate.
To disengage this cruise control, you simply pull the throttle a little, and the spring tension on the sawblade pulls it up and out of the way- the throttle then operates freely.