Ok, so previously I played chain drive pedals with interchangeable cams (Pearl Eliminators), and honestly the Darwins are on a whole other level of quality and smoothness. And, I love the direct drive. But I want to understand how the direct drive acts in terms of cam shape. The default settings seem like they would almost be a inverse eccentric cam, but Im not sure about that.

I believe it is possible to set up the direct drive to behave similarly to a normal eccentric cam based on cam angle setting, but I need to do some more testing. If Dennis has explained the direct drive action in these terms I would be very interested to hear the explaination.

My approach to replicate the feel of a eccentric cam: On an strap drive with an eccentric cam, the effort is less at first due to the pull point being further away from the rotational axis. As the beater moves towards the head the amount of force needed increases as the pulling point gets closer to the axis. On a direct drive, the pull point is always the same distance from the rotational axis, BUT the direction of pull changes. In order to decrease the force needed at the beginning, the angle between the radius line from the linkage connection point to the cam to the axis center, and the linkage should be close to 90°. This ensures that all all applied force is applied to rotational motion. Then as the linkage point rotates around the axis, the angle should increase, or decrease. Either will increase the amount of force needed to continue moving the beater. This may or may not be 100% doable with any DD pedal, but I think the darwin gives the best chance.

I will do some testing and add my findings later. By the way, I also own the strap drive conversion but I want to do this as an experiment and to better understand WHY DD feels the way it does in terms of things I understand (which is cam shape).

Hope this is somewhat interesting.

I found a great explaination Dennis had about the differences between strap and DD and also the way DD behaves in terms of cam and my initial thoughts were confirmed. I will continue developing my adjust.ents for my double pedal to see if I can closely match an eccentric cam and post my results here.

Some of my words from ACDs facebook page (different context)

"Let me try one possible explanation why people maybe love direct drives.
As you know, I have both.
My feet are a bit clumsy as well as a bit heavy.
For the use of triggers it is necessary (and generally it is good) to have the beater some centimeters away from the head while your feed are in a resting position. So it's cool if at the end of the movement the resistance becomes higher.
The spring geometry supports that.
An excentric cam supports that as well, at least a bit.
But since the way->power-ratio of a dd changes in a (co?)sinus-function, dds support that increasing resistance the most. It is easier to play without fail-triggers then, you don't have to concentrate on releasing the pedal after the hit, it supports you very much.
At least for me it feels that way.
The strapdrive feels smoother, more organic, more natural, nicer. (for me)
But it's cool to have both options."

If I' m right...



If the lever or the circle that is connected to the beater reaches the highest or lowest possible point you cannot move the beater any further (theoretically). That's like sin(0) or sin(pi). Shortly before/after that point you have max beatermotion for min footboardmotion. You got most footboardmotion per beatermotion, when the lever/circle points 90° forward like sin(1/2 pi). (backwards would be kind of strange...)

I hope that's correct, school was very long ago...

EDIT: Look here, that might explain it a bit better:

Yeah that all makes sense. This is also compounded by the max out point on DD when the connection point of the drive linkage is at it lowest point in relation to the pedal connection point at the end of the stroke. This can happen when the cam is rotated towards the head pretty far. At this point the resistence becomes effectively infinity since all of the force is perpendicular to the possible direction of rotation.

This ability for DD to "bottom out" is a feature in some cases. But it can also cause too much resistance to the point of losing a lot of power at the end of the stroke.

(Depending on your setup) I think the initial need for more force in DD might not matter since your feet resting on the pedals could move it into the more neutral range unless you lift your feet above the pedal boards often or play quickly with alot of vertical feet movement. But this all depends greatly on the way the pedal is set up and what position the cam is rotated to.

Right now I am doing my best to get my FTW with DD to feel close to my old Pearl Eliminator with an eccentric cam. I initially rotated the cam quite far towards the bass drum head, which gave the pedal more of a standard chain drive feel, but it turned out to be way to close to the bottom out/dead point and made the pedal lose a ton of power and exhausting to play haha (user error). So I lessened the cam rotation and also fiddled with the footboard height which I found helped a lot (i matched the footboard angle to the pearl eliminators). Im still making improvement and will eventually share my full settings for anyone interested.