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Old 01-02-2012, 09:22 PM
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Richards1008 Richards1008 is offline
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Default Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

Hello all,

My name is Alex and I have been playing drums for about 5 years and recently took a bit of a hiatus while my last two years of my bachelors degree was being finished (and as a result I was living in an apartment complex and could not play (or had room for) my kit. I have gotten back into the game now that I am living in a new place and now have my kit down with me while I pursue my Masters degree. I have completed my Bachelors in Automotive Technology and thus have a vast knowledge of the service techniques used in Automotive industry. More on my automotive influence later. I play a DW 5002 double pedal and love the thing however it is an older pedal that I have done a few modifications to, I would like to take some of you through part of my solution to alleviate an issue that has plagued drummers for years when it comes to double pedals.

That damn slave...

For years most drummers have gotten "used to" the lag time and response from that left side pedal. It can be solved by using something like a bi-lateral pedal such as the offering from off-set (http://www.off-set.net/Off-Set/Home.html) This is because both sides have equal lag. Meaning it may screw your primary foot up a tad, but your left will now react equally to your right.

However, what if your not interested in dropping more coin on a new pedal? Or plain don't like the way a bi-lateral pedal is set up?

Well, a lot of our issue comes down to our u-joints...

Here is where my background in automotive technology and education comes in. We all know and love the pair of u joints that we look down upon (literally) when we play drums... they sit on a driveshaft that transfers the motion from our slave pedal to our primary pedal assembly on our kick. But there may be something you don't know...

When dealing with u-joints there are several critical factors in their operation. Alignment and phasing being the two strongest factors.

The first factor we have is alignment. We have to understand that the movement of u-joints is elliptical. This is fine when the u joint is straight, in other words, not having to transfer rotational motion around a corner. But when we use that u joint to do what it was designed to do (the aforementioned "going around a corner") something peculiar happens...
When the u joint input is steady (for example 500rpm) the output will vary, depending on the extremity of the angle. It varies in a sine wave pattern both above and below 500rpm, twice for every revolution. That means that even though the input is constant, our output will speed up and slow down above and below 500rpm.

Here is a basic illustration of this variation... It is a characteristic of the joint


So, what do we do to solve this variation and what does it mean to drummers?
It means whenever you use that slave pedal, if it is not set up or assembled correctly, as the beater moves towards the head, no matter how smoothly you move that footboard, the beater will accelerate or slow down as it moves through its stroke because of those pesky u joints...

Well, there are two things to do about that... Number one this variation can be cancelled out. This is the solution used by most automotive manufacturers. Since automotive driveshafts and driveshafts in double pedals both have a pair of u joints, we can use the other joint and place it "in phase" with the first one. What happens then is the input variance of the second joint cancels out the variance in the output of the second.

We can do this, as long as we employ the second fix... which is equal angles...

When you set up your pedals, set them in such a way that is comfortable for you to play, however take note that the closer the angles are across both u joints, the better chance you will have at nearly eliminating any weird beater speed fluctuations you may be experiencing.

This would be a good example of a symmetrical setup of the ujoints... as you see, from the camera perspective (drum set removed for clarity :-)) The driveshaft is perpendicular and the two pedals are pretty close to being equally splayed from the axis of the driveshaft


This photo illustrates angles being out of phase, notice the slave pedal is at a much greater angle to the driveshaft than the primary...

An angle difference like this is huge, and would cause substantial vibration if this was an automotive application, so yes... tiny amounts like this DO MATTER!

So now that we have all our angles equal, we must put the driveshaft in phase... In order for the u joints to be in phase the yokes on the center driveshaft have to be positioned as so...


This photo of my DW, an example of before I discovered this by accident after the fact.


I never thought of applying this to my drums and since I have it has changed drastically the ease at which I can play the double pedal. IF you notice the shaft is OUT OF PHASE... You can solve this by simply removing the one end from the alluminum center sleeve and turning it ninety degrees so the yokes lined up as in the photo earlier.

Try it out and see what you think, I think it makes a big difference... some may say they see no difference, this will not overcome extra frictional losses from your slave... but it will help you at least gain a little ground on the problem before you run off and buy another pedal.


I wrote this quick, so there may be some questions I'm sure... Any of them please post here or PM and I will try and help you out. I have found that certain pedals with HEX driveshafts (for the sliding mechanism) usually cannot be put into phase without modification to the shaft because of their six sided nature (so in this case its okay to be a square :-P)

More on driveshaft phasing (for those interested) can be found here...
http://jniolon.clubfte.com/driveline...nephasing.html

I wanted to find a video of u joint speed fluctuation but could not find the one I liked, if I do I will post it or make my own, it is fascinating what goes on without anyone knowing it...

Also all photos are copyrighted to their respective owner... I used them... whoops...
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Last edited by Richards1008; 01-02-2012 at 09:24 PM. Reason: Original picture too wide
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Old 01-02-2012, 09:47 PM
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harryconway harryconway is offline
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

No drive-shaft/u-joint issues with my double pedals.
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Old 01-02-2012, 11:36 PM
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

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Originally Posted by harryconway View Post
No drive-shaft/u-joint issues with my double pedals.

Because it's a Bi-lateral design... as mentioned...

Speaking of those contraptions... Something does not seem right about the geometry... Its surprisingly simple for a German product but the way the footboards are set up seems like it would induce lateral loading to the chains and cams. How do the footboards pivot? Do they pivot at an angle that is equal to the angle of the cam shafts? If not that is a very badly designed system that I would think would not survive or be very playable. IF they do pivot at the same angle, well why would you wanna push down at an angle instead of straight down with a standard pedal?


More info? Never seen one in person, just from an engineering standpoint it seems off...
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Old 01-03-2012, 01:31 AM
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

That pedal is just too weird, lol. U-joints on double pedals is why I have a double bass kit instead.
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Old 01-03-2012, 05:09 AM
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

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Originally Posted by zarrdoss View Post
That pedal is just too weird, lol. U-joints on double pedals is why I have a double bass kit instead.
Best fix right there!

Detailed synopsis you gave. Pretty cool. I orignally set up my doubles with U joint symmetry and minimal angles. There are some incredible, high quality pedals out there, with amazing technology.

I use a TRICK Dominator pedal, and the U Joints on that sucker are liquid smooth. No delay or latency at all in the shafts. It better not for the price...
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Old 01-03-2012, 05:29 AM
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

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Its surprisingly simple for a German product...........
German? Has anyone told Don?
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Old 01-03-2012, 05:42 AM
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

Great analysis. That makes a lot of sense. I hadn't considered the influence of the U-joints but the 'phasing' makes perfect sense to a sound guy like me.

What about universal joints? Would they have the same geometric issues?
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Old 01-03-2012, 05:46 AM
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harryconway harryconway is offline
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

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Originally Posted by Richards1008 View Post
Because it's a Bi-lateral design... as mentioned...

Speaking of those contraptions... Something does not seem right about the geometry... Its surprisingly simple for a German product
Best I know, Sleishman has been made in Australia, since about 1971. With about 40 years of having these pedals out on the market ... I think they pretty much got the "bugs" worked out of them.
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Originally Posted by Richards1008 View Post
but the way the footboards are set up seems like it would induce lateral loading to the chains and cams. How do the footboards pivot? Do they pivot at an angle that is equal to the angle of the cam shafts? If not that is a very badly designed system that I would think would not survive or be very playable. IF they do pivot at the same angle, well why would you wanna push down at an angle instead of straight down with a standard pedal?
From what I can tell, they are extremely playable .... but what do I know ? I'm just a drummer. I put my foot on the pedal, and press down, and drum go boom ! Here's a video, of the Sleishman at work ... http://www.youtube.com/watch?v=nwOeWQ2Tdhg

Quote:
Originally Posted by Richards1008 View Post
More info? Never seen one in person, just from an engineering standpoint it seems off...
If you really want to contact Sleishman ... http://www.sleishman.com/html/contact/
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Last edited by harryconway; 01-03-2012 at 08:53 AM.
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Old 01-03-2012, 06:45 AM
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

That's really interesting. How 'bout just adding a second bass drum that you play maybe 20% of the time? ;)
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Old 01-03-2012, 06:47 AM
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

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That's really interesting. How 'bout just adding a second bass drum that you play maybe 20% of the time? ;)
Great idea for home use, but not so great for carrying around. :)
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Old 01-03-2012, 07:00 AM
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

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Originally Posted by sticks4drums View Post
Great idea for home use, but not so great for carrying around. :)
Sure. It probably wouldn't work on a small bandstand either, but looking at the research that's just been done, it's critical for the u-joints to be in perfect symmetry, and how much on a rushed gig will you be able to get it really perfect? So I say six of one, half a dozen of the other. It's almost easier to set up two bass drums at a good ergonomic angle for your body than it is to make sure your u-joints are in harmony, eh?
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Old 01-03-2012, 09:01 AM
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harryconway harryconway is offline
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

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Sure. It probably wouldn't work on a small bandstand either, but looking at the research that's just been done ...
Well, all the "research" and "field testing" I've done .... I know this ... I carried two kick drums around for 15+ years . and no friggin' way am I ever gonna do that again (even for just 1 show) ...
As far as small stages ... if the stage was that small, then it became my drum riser ... and everyone else stood on the floor, in front. They didn't call me Harry Ballz for nothing ...
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Old 01-03-2012, 09:20 AM
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

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Originally Posted by harryconway View Post
As far as small stages ... if the stage was that small, then it became my drum riser ... and everyone else stood on the floor, in front. They didn't call me Harry Ballz for nothing ...
Than that's what I'm gonna do!
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Old 01-12-2012, 07:35 PM
lildrumr lildrumr is offline
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

Hi, there! This is extremely interesting details to know! Also interesting is that Axis suggests that you may adjust your slave pedal height independantly by rotating the extention rod, since it is round.
I have a question: Will the length of the extention rod affect the power or speed?
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Old 03-29-2012, 08:36 PM
RcKDrUmm3R RcKDrUmm3R is offline
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

I would think that, according to this article, you shouldn't rotate the extention rod too much because the slave side of it should be equal (angle) with the right side that attaches to the main pedal.


Quote:
Originally Posted by lildrumr View Post
Hi, there! This is extremely interesting details to know! Also interesting is that Axis suggests that you may adjust your slave pedal height independantly by rotating the extention rod, since it is round.
I have a question: Will the length of the extention rod affect the power or speed?
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Old 11-11-2012, 11:46 PM
ArtSweatBlood ArtSweatBlood is offline
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

I'd just like to express my gratitude to Alex aka Richards1008 for explaining this concept here.

I had tried at least a dozen different things to get the response of my slave pedal to more closely match my master (I'm using a DW 9000). It is thanks to your explanation here that I actually realized angling to be so significant, and thus the problem in my situation.

Rock On
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Old 12-27-2012, 10:01 PM
RcKDrUmm3R RcKDrUmm3R is offline
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

The angle of the u-joints def. make the problem worse but I don't see it completely correcting it. When you play the slave, the energy has to travel from the pedal through the linkage. Not to mention I think the weight of the linkage has something to do with this as well. Most of these high end pedals, mainly direct drive ones, have some pretty heavy linkages. Just my theory though......
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Old 12-30-2012, 11:02 AM
Winegums Winegums is offline
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Default Re: Double Bass Pedals - Slave pedal lag, and why your tiny u joints could be a big problem

I have a pearl Z-link added on to my Iron Cobras. This rose from the problem of lag limiting my left foot speed. The original drive shaft had so much lag and so much mass it slowed my left foot by an amazing amount of bpm and also killed the accuracy of my kicks. Once I added the z-link I could reduce the spring tension and cobra coil settings to something closer to my master pedal. The results were mind blowing it was like a barrier was removed from my left foot. There's something to be said about a lag free drive shaft, not to mention super low friction. Also I found your points on drive shafts to be enlightening, they apply just as much to cars as kick pedals if the laws of physics are fair.
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