Rocking plate for indoor trainer

[kgreene10]

I’m interested in making a rocking plate for my indoor trainer to let the bike sway like the Kurt Kinetic Rock n Roll does. When in a fixed, immovable position, my knee just kills me. Unfortunately, I’ll need to do more indoor training this winter if I want to be in race shape this spring.

There is a retail option but it ships from abroad and seems like it should be easy enough to build yourself. But I’m not handy and really have no clue. Would handy types consider taking a look at these photos and rendering an opinion: http://www.bikeacces.com/127468127463rocking-plate.html.

What’s the air spring that’s in there? Would wood work instead of metal plates? If so, what kind and how thick?

Other ideas for a simpler approach very welcome too.

[batman1425]

I think you could replicated something reasonably easily.

For the base I think you could get away with 1/2" plywood and for the top, the surface that your trainer would sit on, I'd go with 3/4". Its going to be heavy, but I'd want the extra stability on the load bearing surface so that it doesn't twist and flex under load. A few well placed metal straps to secure it to the base should be all you need to keep it from sliding around.

The key will be the suspension system that separates the two so that it moves in the direction that you want and has a component of self centering. I'd try a 3 point suspension system, 1 in the center of the back, right under the resistant unit, and two in the front, 1 on each corner. For the suspension, you'll need to experiment a bit to find something that will compress reasonably well under load, but also rebound. Kinetic does it with an elastomer at a single point in the back, the model you show use the air bags. Off hand, an easy option might be something like a tennis ball. Make rings that you attach to the top and bottom decks which will hold the dampers (tennis balls) in place. You could try tuning the rebound by poking holes in the tennis balls to give them more squish if the whole setup ends up too stiff. Lastly, I'd run a few carriage bolts through the whole thing and just lightly snug them up when the setup is loaded with rider weight to keep the whole thing from slipping apart while in use.

In total, probably 40bucks of parts and an afternoon to put it together, but would probably take some time to tinker with to get it right for your specific weight.

Edit*** Another option that I've considered in the past, get a bosu ball, and build a platform that sits over the top of it for your trainer to mount to and an extended front wheel riser to match the height. The downside is unless you already have a bosu ball, the cost will likely outweight just buying the Kinetic (or similar) system.

[one60]

Would setting the trainer on a rubber floor mat used in retail & workshops give you sufficient movement?



https://www.uline.com/Product/Detail...E&gclsrc=aw.ds

[kramnnim]

This has been discussed quite a bit in the Zwift Riders Facebook group.

The design that I was planning to try used a pipe as a pivot between the plywood squares, and tennis balls to act as springs.

[carpediemracing]

I need to do a version 2 of my set up, an adapted KK R&R set up made from an extra CycleOps frame (initially used with a Fluid2 head, now it has a KK Road Machine unit). With a KK rock N roll type set up there are a couple critical things. First, you want to avoid any fore-aft rocking motion, i.e. the front of the bike tilts down - I have to imagine that any "cushion under a plate" set up will have this fore-aft motion. I know my trainer does. Second, I found that a lazy susan under the front wheel helps - you steer your bars to tilt the bike, sort of like in real life. This is why the KK R&R front wheel holder is a circle on the ground, so it will swivel.

With the rocking trainer I found myself pushing even more than normal. Some fellow Zwifters asked about my very low cadence, in the 70s for the most part. On a rigid trainer I'm typically 95-105 rpm. I use pretty long cranks for my leg length, 28.5" inseam and 175mm cranks, and with 170s I'd be more like 110-115 rpm.

The trainer:


The swivel under the front wheel (about $7 at the True Value where I worked, rated to something ridonculous like 1200 lbs):

[carpediemracing]

Another thought.

The pivot point needs to be slightly above the rear tire contact point (imaginary point if on a direct drive trainer). Pivoting at the tire-ground level is what the bike actually does, if you look at bike-road relationship, but if you look at bike-rider relationship the bike actually rocks at about the BB height. The tires zig zag on the pavement to keep the BB under the rider (you can look at tire tracks going up a hill, like in the rain, and when the tire tracks will start to slalom it means the rider just got out of the saddle). If you set it up so the trainer rocks at the tire-ground height the BB will end up swaying back and forth pretty dramatically, definitely not ideal. It would be ideal if the rocking axis was at about BB height, but this means the trainer would be sliding left-right during the rocking motion.

My goal with v2 of my trainer is to have a second pivot up front, connected to the rear frame via a strong plate/tubing. The idea would be to move the pivot pretty high to get the pivot axis closer to the BB, and to eliminate any fore-aft rocking by having two pivots. The second one would realistically be in front of the BB.

Although I've done some sketches I don't know how I'll accomplish this. Also my welder friend no longer has access to the plasma cutter and welder he used to make my v1 trainer.

Finally I want to massively increase the flywheel weight. I want more resistance when jumping hard.