Hello All:
Would any of you happen to know a source for the 48mm "Overdrive" bottom bracket shells? Here is a link to the spces:
https://isisdrive.com/isisoverdrive/background.htm
Thanks,
Jim

Those drawings are over 12 years old. I'm pretty sure that standard never really caught on and is effectively dead now.

Yes, I agree. But, I have a source for the bottom brackets and would like to use them in a very heavy duty lab ergometer. Surely some parts supplier has some shells in a bin somewhere?
If I can't find one I can have it machined but would love to just find the ready made shells.
Thanks,
Jim

I would guess that we are now at war with isis that the bottom bracket would be hard to source.

Yeah, I have been wondering when Homeland Security would notice my search words and show up at my door.

I don't really remember this "standard." I assume it's not standard BSA threaded BB, which means you need tooling for post-weld facing/boring. Hard enough to find that for some of the more current "standards." Probably best to look to something more current. And there is nothing wrong with BSA standard BB other than people like creaking bottom brackets.

For anything approaching normal use I totally agree. All my bikes still use BSA square taper bbs. BUT, this ergometer is well outside of any normal use. It is designed for eccentric (resistive) cycling. Some guys will do up to 900 watts for 20min. Yes, you read that right. For the chainring, cog, and chain we use #40 industrial stuff. The system is driven by a 3hp motor. When we do a training study we replace the standard bb every week so that it doesn't fail during use. Even then they sometimes fail.
These overdrive bb's look like they might hold up much much better.

900 watts for 20 minutes? 746 watts is one horsepower; these guys must be brutes.

Elite downhill skiers. Real Quadzillas. The metabolic cost of eccentric cycling is very low. Like 1/5th what you would expect for regular concentric cycling.

I'd like to see some evidence for that.

It is extremely unlikely that anyone can produce 900 watts for 20 minutes: it would require 10 watts per kg from a 90 kg individual. Even for elite XC skiiers, who have the highest aerobic capacities of any sport, 7 watts / kg is the accepted limit for those not relying on "assistance".

Also, since the accepted figure for aerobic conversion in cycling is about 0.22 , for your process to be 5 times as efficient would result in a conversion > 1, obviously impossible.

I figured someone would call BS. Fair enough, it really is hard to get used to. Here's a link to the study by Gross and colleagues where skiers did 850 +/-70w for 20min. Its strength training not endurance.
www.researchgate.net/profile/Micah_Gross/publication/44594167_Effects_of_Eccentric_Cycle_Ergometry_in_Alpine_Skiers/links/0deec529f22a193ebc000000.pdf

"page not found"

Corrected Link

Thanks Stan! Look at figure 1 for the training load progression. Eccentric cycling is fundamentally different than concentric. Use google scholar and look up work by LaStayo. He has 70-80yo women doing 400w.

Hence my interest in super robust bb's. So.... anyone know where I can get an Overdrive Shell?

I find it hard to believe, but perhaps I'm missing something. We know, for example, that Lance Armstrong’s power output on Alp d’Huez in 2004 was calculated as 495W – this was presented as a scientific paper at the ACSM congress in Nashville in 2005. It's hard to imagine these 15 - 20 year old skiers could muster 900 watts for 20 minutes.

Tour de France power estimates

Ever do any trail running? Huffing and puffing at low speed going up? Running like superman downhill with a smile on your face? Eccentric cycling is like running downhill. Concentric is like running uphill.
When you run uphill you do work just like you do when cycling. When you run downhill you absorb work and only perform a braking action. That's the same as eccentric cycling. If you happen to be in Salt Lake City drop by my lab and try it out.
Does that help?

I'm still having trouble with the concept. A locomotive hauling a load of freight up a grade develops a lot more power (watts) than that same locomotive and its freight coasting down the grade assisted by gravity, no?

OK, so the motor is providing 80% of the 900 watts, now it makes sense.

Oh; you mean the 'motor' isn't the cyclists' leg muscles?

It reads like the cyclist is resisting the pedals on the crank arms with the crank being powered in the opposite direction by an electric motor. Now I'm really confused.

You've got it exactly right. The 20% is more like stabilization cost. Holding yourself down on the erg.

Sounds like a politician running for office. "I'll lower taxes by 80% and get 100% of the services covered" Andy.

If you are not familiar with eccentric contractions, think about running down a very steep hill: your quads are trying to contract while they are being extended.

The physically hardest thing I ever did was running the course in this outline: that last downhill is murder, especially when you've already got >60k in your legs.

OK, Mark. Thanks; now I get it. Sort of. That descent looks like about 200 meters elevation drop in 3 km.

Good one, Andy.

I confused my trainer and managed to put out 1300 watts (for a few seconds) hoping it would automatically reduce the resistance. But the bike fell off instead. I think the axle is the big problem with high power, maybe something like a current shimano 105 would work better