OK. Because I am insane, and also a woodworker, I have decided to build my own set of rollers. I am going to glue up hard maple and make large rollers, probably in the 6-7" diameter range. I am doing this to make a very smooth ride, and because again I am insane.

Now to my question. I have ridden straight rollers many years ago but am not the dedicated cyclist I was 20 years ago. When I turn these on my lathe, should I make them with a very slight parabola so that the riding is a bit easier? Or is this cheating or in some way going to make for a less effective training experience.

Has anyone out there ever ridden on parabolic rollers and what was your experience? Thanks

eh...I'm a total newbie at riding rollers and I'm having no issue with non parabolic rollers. I wouldn't bother.

I would suspect that the tires would climb up the sides, making it harder to keep a straight line. Think of riding up a smoothly-shaped curb.

I haven't heard of such rollers, so maybe that's why. I'd normally say that it wouldn't hurt to try, but in this case, it might.

How will these be smoother than machined aluminum? The variation from humidity will probably be more than the tolerance in machined Al. 6-7" is rather large and won't provide very much resistance. I wouldn't bother with a parabolic shape. If anything just make them a bit wider. Since they are totally custom, you might as well build in free-motion, a large flywheel and make sure that the bike is level by offsetting the rear wheel rollers higher.

not true from what I have heard. I have heard its not a matter of easier, but it does keep you riding more in the center if you start to drift to either side.

Okay, so the parabolic idea is probably gimmicky. I know I have run across them somewhere, but I just need to learn rollers again. Points well taken.

As far as the smoothness. I am thinking the larger the diameter of the rollers will definitely impact smoothness, and since I am going to build them, why not go really large (Kreitler boasts their 4.5" are very smooth, so why not. Also the way I will construct, with kiln dried quarter sawn maple, they will be VERY stable. And heavier than any machined aluminum. All good things, I think, but could be convinced otherwise.

I really like the idea of building in free motion. Consider it done. Winters here in Maine are long, and building furniture all the time gets boring... I need a hobby.

Surley beat you to it (From interbike 2011)

Because you won't have enough resistance. Bigger rollers equals lower resistance. Look at the Power Curve for Kreitler's 4.5" rollers. If you get lower resistance than that, you'll need to add a resistance unit.

It's been done before, but I don't know the real world pro/con issues.

In addition to that, the hardwood will produce a heavy flywheel, which will ruin your spin. I made the mistake of experimenting with Kreitler's flywheel (it was on Ebay for less than $30, but I soon found out why); my happy fluid spin deteriorated into that of a choppy, Parkinson's-afflicted newbie-triathlete.
But if you are insane, this is perhaps a perfect idea. Good luck!

You havent heard of Parabolic rollers?

https://www.performancebike.com/bikes...8_20000_400134
https://www.cbike.com/elite_arion_ita...rollers-1.aspx
https://www.cbike.com/elite_parabolic_rollers.aspx

First, parabolic rollers are for wussy.

Second, when you make the rollers, make certain you provide some way of balancing the cylinders. It will be essential the rollers be balanced; they are spinning quite fast when you have the bike up to speed.

Third, I have no idea why a flywheel will "ruin" one's spin. All you are doing is simulating the momentum you normally get by having the bike in motion on the road. Stationary bikes have only the momentum of the wheels and rollers keeping the wheels turning through the dead spots of the pedal stroke. Bikes in motion have the momentum of your body weight at speed to keep the wheels turning. Adding a flywheel to rollers simply mimics what is already present by a bike in motion.

It was a lot easier to simply jump on the rollers and just yammer away at the pedals with the flywheel mounted, but rollers (with resistance) are for working to remove dead spots in the pedal stroke. Instead of the whirr-whirr-whirr coming from the Killer-Headwind fan, I focus on a steady, fluid whirrrrrrrrrrrr. And the more I worked on that, the more my FTP climbed.
What works for me may not work for everyone, but my spin got catastrophically worse during the 2-3 weeks when I used the flywheel, and it took a few weeks of focus to get the fluidity back.

Im intrigued. What bearings are your drums going to ride on?? Im a woodworker myself...

I bought Nashbar parabolic rollers for my wife, and I have ridden them a number of times. They are only raised towards the outsides, and are flat in the middle. The benefit is to keep you from going off when you start daydreaming. You get strong feedback as the tire starts to roll up and then slips down the parabolic edge. It isn't enough to unbalance you though. I think they are a good idea for watching TV or otherwise vegging.

As had been posted many times, there is no reason to buy a resistance unit. Just let air out of your tires and/or put an old towel/carpet remnant under the rear roller. Works perfectly.

Frequency of posting on BF is hardly a indication of truth.
The fan on this resistance unit is adjustable and uses the power you are generating to blow cooling air directly on you.

$150. For the turd that needs everything. Even if it were free I'd rather shift gears and have my naked wife fan me.

Me too, but I like to give her a night off now and then.

There is really no reason to work on eliminating dead spots from your pedal stroke. Your leg motion only need be efficient. This is not the same thing as trying to maintain pedal force through the natural deadspot.

And as I suggested, if working with the flywheel mounted rollers for a couple weeks made your spin go to crap, then you should be prepared for the worst when you take your training outside. I mean, there is no better inertia generator than 200lbs of body and bike flying through the air at 20mph.

One more thought on the deadspot...

Think of it this way: what major muscle group is directly enacted in dragging your foot through the deadspot of the pedal stroke? Probably your hamstrings, and inefficiently at that. By trying to get rid of the "whirr-whirr-whirr", all you are doing is gearing down so your cadence increases while decreasing your pedal force in the power portion of the stroke and increasing the pedal force through the deadspot using a group of muscles which have little leverage to make that motion. FTP rises simply because you are one of those who benefits from an increased rpm.

A better plan is to focus on the power portion of the pedal stroke where you have the quads and the glutes working with good leverage and increasing your coordination for recovering your foot as it rises at the back end of the pedal stroke so there is no pause at the bottom. A "dead spot" means a dead spot for power production. This doesn't matter. What you don't want is an actual pause in motion at the bottom of your pedal stroke which is what people refer to as a "choppy" or "square" motion.

I guess I was thinking of a gradual curve all the way from one side to the other, not just small lips out at the ends. Either way, I think the E-Motion rollers are better at not letting the rider fly off.

Thanks for all the feedback. I see that my rationale was COMPLETELY wrong with the larger drum diameter. I actually thought I would be increasing resistance, but obviously I took physics way too many years ago. Makes sense now.
Maybe I just abandon the whole idea and buy a set. I was just looking for an excuse to reinvent the wheel, and I guess maybe buying a set of rollers and turning them into free motion would be time better spent.
Anyone want to try and give me a reason to continue on the solid maple roller quest? As far as balanced construction goes, these wooden drums would be very well balanced, and it seems like they would act more like flywheels themselves than the aluminum versions. I'm quite sure they would be heavier (even at 4.5") but is this a benefit?

That's easy: they'd be cool...and you're insane.

Thanks for your thoughts. Really, no snideness at all.
Another thing about cycling I love is that it is different things to everyone, and what works great for one, is crap for another.
It was actually the top of my stroke (11-to-2 o'clock) that was weak, not hamstrings. When I started focusing on hip-flexors, aductors and abductors, my flat spot assuaged and I had another FTP breakthrough. True, lessening my weakspot did allow me to pedal more comfortably at higher rpm, but my avg cadence for the test went up only 3 or 4 rpm on the 20 min test.
It was shortly before learning this from Nate Loyal, that I'd experimented with the flywheel.
I absolutely concur that my ~200 pounds @ 20mph is a colossal amount of inertia, but after looking at 1.5 years of workout data, my avg cadence has remained roughly the same, but my avg & lap wattages have gone up while avg HR has gone down. (At least this was the trend before meeting my gf in May and my training going into the toilet.)
What works for me might not work for everyone, but I'm convinced that flywheels cause stagnation in the minor muscle groups, and we're better off without them. The fact that I was able to get the stupid thing in nearly new condition for $30 delivered (and the freight was more than $10), suggests to me that someone else drew a similar conclusion.
Thanks again. Peace & safe riding.