Rocker Plates for Trainers

Equipment
1183

They will work to a point. The potential problem is the static friction inside the cylinder assembly. That “stiction” will alter the feel when compared to the simple inflated ball/springs that most of us use.

My preference for rocking feel is minimal centering force, and not damping. That is to allow for nearly seamless transition from side to side, and from level to angled. I dislike slow motion or a “blocky” feel that comes from some spring setups.

This can all boil down to personal preference, so the cylinders can work, but I expect the motion to be damped in an undesirable way. Maybe it will be minimized depending on the size and leverage ratio, but it will likely have more resistance to motion than our other options.

1184

I was trying to figure out a way to allow rocking while limiting fore-aft movement that didn’t copy Cycleops clever setup. This is what I came up with. Cylinders might not be the best spring, I’ll find out. Could always go to active control :slight_smile:

1185

Put it together. I’d love to see it. :smiley:

1186

Hey, kids. I had joined the Facebook rocker plate group, but dropped because I had a serious concern about it: the point where the tires hit the road isn’t fixed – it moves slightly to the left and right. If you look at a bike, straight on from the front, it sort of acts like a see-saw, with the pivot being a point around the bottom bracket.

This is fine when you’re in the saddle, but I’m really worried that when I’m out of the saddle in a sprint, that the motion will be really unnatural. Even worse, what if I learn to sprint like that, and then take it out on the road, or a crit course?

Basically, I’m trying to find out if anyone has found that doing out-of-the-saddle sprints on a rocker plate feels unnatural and/or if it has hampered their ability to sprint, outside.

1187

I likely have the most time on a rocker plate (since Jan 2016) and have done more testing on different designs than just about anybody. I understand your concerns, but they are not an issue, IMHO.

  • True, the bike is not fixed outside while rolling. The amount of lateral movement of the wheels (front and rear) varies with the particular rider and the amount of rocking used (standing or seated), as well as their steering input to maintain a forward direction.
  • What does that all mean? That there is no single answer for how much lateral movement happens. It can and does vary even with the same rider and bike combo. Nothing is static or completely repeated exactly the same.
  • As such, there is no single right answer for where the pivot should be placed. I am experimenting with alternate pivot locations, but primarily in an aim to get better “feel” that is more like we generally experience on the road.
  • I do agree that the pivot for real outside riding is above the ground, but the BB is not the solitary location for that, even when standing. Yes, the BB becomes a major load point when we shift off the saddle, but that does not automatically make the the instant center of pivot rotation.
  • I feel the actual pivot is more complex (even dynamic) and not a single point. It will shift from rider position and input via the bars (both rocking and steering) and pedals. I have a theory of the actual shape and location of the pivot that I want to replicate with a very different rocker design. I just need more time to make the darn prototypes.
  • I will include a video of my use with a “below ground” pivot location. After years of tweaking this design, it is the best I have used at the moment. I know it can be improved and that is what drives my other pending designs.
  • As to the potential negative impact of a rocker on outside technique, I think that is a non-issue. First, recognize that any rigid trainer is almost certainly worse in those terms. The method we adopt to stand and sprint on a fixed trainer is nothing short of odd and very different when compared to outside.
  • That is the reason I feel a rocker is an improvement as we get away from that unnatural rigidity, and add at least some motion, that gets us closer to outside feel.
  • https://youtu.be/gt2XO4NVZEo

Let me know if I have addressed all of your issues. Happy to chat more about these. It has been a huge part of my mental time and effort these past 3+ years.

1188

I’m not following any situation inside or out where the pivot point is the bottom bracket. But regarding sprinting concerns: the sprinting motion on a rocker tends to be reversed. It rocks towards the side you are stepping onto, where as outside you push the bike away. I say tends to because if you think about it you can still do it the “correct” way, it just takes some thought to do it. I don’t really care though and I just sprint whatever way happens on a rocker. It hasn’t impacted my outside sprint that I’m aware of, and my sprint is the strongest tool I have in races, both outside and Zwift.

1189

bicycles stay up because the rider steers the tire contact patches under the rider’s center of gravity – on average. That’s a very complex motion if the rider is sprinting out of the saddle. But as a first approximation, saying the pivot point is at the tire/road interface is reasonable.

1190

That is the easy assumption, and correct in some cases, but I think standing leads to a different effective pivot location.

If you ride on or next to a straight line, you will often see a snaking motion of the front tire back and forth. This propagates to the rear wheel as well in a reduced amount of lateral snaking motion.

That lateral motion of the tire on the ground effectively shifts the functional pivot location above the tire contact with the ground. It will ultimately be somewhere between that and roughly the hub height.

It definitely varies with the total lean angle and how much steering input the rider uses in conjunction with the rocking. It is very complex and something I have watched closely during many, many miles on the road… in an effort to better understand what really happens.

I have a plan to capture all of this with cameras and other measurement tools, but it is complex to catch all the motion and inputs in a way that keeps the info sync’d for proper review. But my “seat of the pants” observations capture much more motion than most people realize is happening.

1191

I agree with you

1192

I’ve been thinking about @mcneese.chad’s “T-Plate” rocker design (see his post from December 17, 2018 at 6:45pm). I’ve been thinking about what to use for the rigid pivot along the center of the rocker plate, and I immediately thought of painter pyramid stands:

From experience, they are surprisingly strong – they are rated to hold up to 200 lbs, and I assume that if you use a lot of them, they can support considerably more in the aggregate. If you look at the close up picture, you will see that they have tabs on the side with holes so you can screw them down. I’ve been considering lining up a bunch of those on top of a 2"x4", screwing them down so the peaks of the pyramids are perfectly aligned, then throwing a deck on top and adding air pods or other suspension on the sides.

I have three questions for those of you with experience in building these:

  1. Would the pyramids be better, worse or about the same as using some of the McMaster Carr cylindrical Vibration Isolation Mounts that some people have referenced above? On the one hand, the vibration mounts might be more forgiving, on the other hand, it seems like they might result in more bouncing than a solid pivot.

  2. Is there general agreement on what works best for the side suspension? I’ve seen references here to tennis balls, foam, inflatable exercise balance pods, and playground balls (5" or 8"). It occurred to me that racquetballs might be another option. I’m leaning toward 8" playground balls. Thoughts?

  3. Any advice on the preferred height from the floor to the bottom of the deck (or for those using a bottom deck and a top deck, the space in between the decks)? The painter pyramids are about 2" tall, which I’m guessing is a little low? A standard 2x4" is 1.5" high, which would give me a total of 3.5". That seems like it should be plenty. Again, thoughts?

Best,
Adam

1193

Hi all, first post here at TR. About a year ago I built a fantastic rocker plate thanks to @mcneese.chad and the Facebook rocker plate group using pillow bearings/shaft and two wheelbarrow inner tubes to use with my KICKR. A transformative experience that I HIGHLY suggest anyone who is thinking if they should go for it or not … GO FOR IT! I train for half and full distance triathlons and this setup is glorious.

I was looking into getting a Wahoo CLIMB, but then read that not only is it not recommended to use a CLIMB with rocker plates, it will void the warrantee! I called them to discuss this, and they added that it is equally not recommended to use rocker plates with the KICKR because of the ‘stress’ that it will put on the bike frame. ?!?!

I searched this group and elsewhere for any mention of people’s experience with this issue and haven’t found anything. I myself have not had any problem with my Cervélo P2 using rocker plates and the Wahoo KICKR (newest) or KICKR 2016. In fact, my common sense tells me I’m putting LESS stress on my frame.

Any wisdom from this group? Is this concern being seen by anyone? Anyone using a CLIMB with rocker plates?

Thanks in advance…

1194

@jpveloct What size inner tube did you use? And can you say any more about how you decided to use wheelbarrow inner tubes vs. something else?

And what did you use the pillow bearings for?

Thanks!
Adam

1195

Well, it turns out to research the answer to your question, they weren’t wheelbarrow inner tubes. Instead, they were: Martin Wheel 480/400-8 TR13 Inner Tube for Lawn Mower and work very well. I first tried small gym balls, but these work much better.

3 pillow bearings are bolted to the top plate and 4 supports to the bottom plate with a 20mm rod running front to back as the ‘pivot’. See attached pics!

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1196

  1. The pyramids would be good for a “T-Plate” rocker. I would mount them upside down under the top plate, and the point would be the pivot on the floor.

    • The vibration mounts are meant for use with a “Double-Plate” design. You attach the mounts between the plates (like a sandwich) and add springs. One plate is on the floor, the other supports the trainer.
    • The point is that they are VERY different rocker designs overall.

  2. Leveling springs run the range, as you note, but I really like inflatable balls for their feel and maximum adjustment options. That size listed is perfect.

  3. Height is optional. Taller will give more max lean angle. I like 2" min up to about 3" max.

1197

(crazy… the second picture showing the pillow bearings and inner tube is both upside down, and backwards!) Also note, from the Facebook discussions, the KICKR is slightly offset to have the bike on the centerline of the pivot and counterweighted to be neutrally balanced. The KICKR is also set to a smaller wheel size to have the rocking motion to be more inline with the actual wheel size when out on the road… if that makes any sense…

1198

I firmly believe that use of a rocker plate will reduce the peak loading (and related stress/strain) on the frame, when compared to a rigid trainer.

I wish I had access to the tools necessary to test my theory. But once you free up the basic degree of freedom with a rocker plate, and assume related balance from the rider, I feel you significantly reduce the peak loading on the frame.

It is especially important for any rider planning to apply sprint type efforts in or out of the saddle. These efforts lead to much more body movement, and even with the “best” indoor riding technique, seem to lead to significant side loading on the frame. That restriction at the rear axle is unnatural and not at all what the bike sees outside. Letting it float via a rocker will probably lead to a huge decrease in stress under those hard efforts.

1199

@mcneese.chad Thanks for the feedback, Chad. The only problem with mounting the pyramids to the bottom of the top plate is that it could make balancing complicated, since the pivot point (the strip of pyramids) will be locked in place. By mounting the pyramids to a 2x4" (with the tips pointing upwards), I could experiment with different lateral positions. But of course your way would be more stable and make it easier to move the rocker plate if needed. Do you think I will be able to adjust balance by just putting a weight on top of the deck when I’m done? Or should I install the pyramids slightly off-center?

I’m getting pretty excited about this idea. Seems like it should be possible to put this together very cheaply with only a few minutes work…of course, I’ve tended to think that about things before that turned into long, hard, expensive projects!

1200

Thinking about it…maybe I can just compensate with the inflation pressure of the balls…

1201

Yup, air pressure works, as well as adding a counterweight (the better options) to get the whole deck balanced. It is best to keep the pivot point directly under the bike and set pressure or weight.

1202

@mcneese.chad I put together my T-plate rocker today. Basically just a strip of plastic painter pyramids screwed to the bottom of my deck. Under static conditions, they strike me as impressively strong. I think those ancient Egyptians were onto something…:stuck_out_tongue_winking_eye:

However…there are a couple of issues. (It wouldn’t be any fun if there weren’t any issues, am I right?)

First, the pyramids themselves aren’t very tall. Maybe 2 inches at most. And the floor of my basement is carpeted. It is shallow, dense carpeting, more akin to what you might see in an office, rather than plush shag capeting, but it’s enough that I would expect the pyramids alone to penetrate about 1/4". To get some additional height, and avoid incurring my wife’s wrath by turning the carpet into swiss cheese, I decided to put a strip of 3/4" thick plywood underneath the pyramids (the strip is only a couple inches wide).

I put two 8" playground balls under each side (total of 4 balls) and inflated them to a level that seemed appropriate (maybe 1/4 to 1/3 to inflated).

First I stood on the deck and rocked back and forth. I would say that the way the balls are inflated, the pyramids just barely touch the strip of plywood. Moreover, because the plywood is relatively smooth, the pyramid tips “skate” across the plywood, rather than being anchored and serving as a fulcrum for rocking.

I put my trainer and bike on top just to try it out. I was actually quite pleased by the stability and degree of motion. (For what its worth, I do NOT want crazy amounts of motion or lean. I probably only need or want a tiny amount. Just the bare minimum necessary to vary the forces on my ample, if rather delicate, bum.)

So I’m trying to decide whether to use it as-is (where it essentially functions as a “wobble plate” rather than a “rocker plate”), or whether I should remove the plywood underneath and deflate the balls further, so that the pyramids are anchored by the carpet and can serve as more of a fulcrum.

Thoughts? I assume that my current setup will have undesirable “bounce” during a workout? (Though note that the pyramids do serve as an effective limit on the amount of bounce possible. If the balls compress more than a minimum amount vertically, the pyramids prevent further downward vertical motion.)

Also: I still have two more playground balls. Better to use them, too? Or is four probably sufficient?

Right now I have the balls located closer to the outside edges of the deck. Better to move them closer to the center axis?

Thanks in advance for any advice you can offer!

Best regards,
Adam