IPS Questions
 

My wife and I recently acquired a used Terratrike Rover Tandem. The trike is equipped with an Independent Pedaling System (IPS). The captain's crank has 170mm arms, and the stoker's crank has 145mm arms. The 145s work well for my wife, but the 170s are long for me, and I'm finding them a bit hard on the knees. (I run 130s on most of my recumbents to keep knee flexion relatively low.) So, I want to go shorter. I see two options. One would be to use crank shorteners. The other would be to replace the current captain's crankset with a non-IPS crankset. The advantage of the second option is that it would enable me to run a smaller chainring, effectively lowering the gearing on the bike, which is too high for some of the hills around here. The disadvantage is that the captain, as I understand it, would lose the ability to coast while the stoker was pedaling, although the stoker would retain the ability to coast while the captain was pedaling. Is that right? If I do go with shorter cranks and a smaller chainring, I'm assuming that my cadence would increase. This would require the stoker to increase her cadence, too, quite possibly beyond her comfort level. Is there a way to compensate for that, possibly by changing out the timing ring on the stoker's crank? If so, would I need to go larger or smaller? (I'm guessing larger.) Thanks in advance for any and all advice.

IPS in general gives me a headache, but I can usually work it out with some coffee to help. Your system looks like your chainring affects only your gearing. The Stokers chainring affects both of yours' gears. Pretty similar to the way it is on 'conventional' tandem drive-trains. On your system your 'timing rings' are not independent. It gets to be a mess changing things around. But since you aren't in a fixed Captain/Stoker link it could probably work.
I'll admit a bias against IPS, even simple systems like on the Terratrike. That said, shortening your cranks with crank shorteners allows you to preserve IPS on your trike. I don't know if you can get to the 130's but at least into the 140's. I don't think it's worth it to do more. I wouldn't, however, argue strenuously against getting some conventional used cranks from a bike co-op and forego IPS altogether. Has it been your experience that your cadence increases when/if you shorten your cranks and/or lower the gearing? I personally don't think it does. What I see is that your cadence stays the same and you go slower. And that's fine. But if you ride with others it may start to seem like you are always chasing them.

It has been my experience that cadence increases when I use shorter cranks and/or lower gearing. I just spin the smaller circle faster. Anyway, I've swapped out the 170 IPS captain's crankset for a set of 130s with a 22t small ring. Feels so much better on the knees and climbs so much better when I'm on the trike by myself. Not sure what's gonna happen when I add my wife/stoker to the mix. It might not be pretty.

You might look into this:

Short Bicycle Cranks

Thanks for the tip. I've ordered short cranks from Bikesmithdesign in the past.

Not sure if I should start a new thread for this but how do I get IPS on my tandem?

Freedom Rotation Crankset
 

Normally, I'd say you can't. But then I remember this couple has the subject crankset on their carbon full suspension:
(skip to 1:30 for cranks)
I've never looked into the cranks, but it seems like a pretty straightforward retrofit.
A reseller:
https://store.mscbikes.com.au/produc...et-for-tandems
Good luck

https://cimg3.ibsrv.net/gimg/bikefor...4189dfa113.png
Literally blurted out HOLY COW when I saw the price. I can almost buy 2 of my tandems for that price. Maybe when I’m really old and broken I’ll get this so the younger missus can pedal for me

If you have your heart set on getting IPS then you need to be ready to pay some money to get it. Here is why:

1. Most IPS systems use a right-side sync chain design. Your Dualie (like most tandems) has the sync chain setup on the left side. So at minimum you are going to have to convert your front crankset to a right-side drive before any IPS system will work.
2. Your Dualie (like most tandems) also has a triple crankset in the rear which requires a more complex/expensive solution than if you just had a single drive system. However if you are willing to give up the triple in the rear then you might be able to reduce your cost.

To set up your stoker for IPS with a single chainring crank, here is one option I found:

• TerraTrike Rover IPS Rear: https://www.bikepartners.net/crankse...ml?id=65194428

To set up your stoker for IPS with a triple chainring crank here are 2 options I found:

• TerraTrike Pro IPS: I cannot find anybody selling these. You might have to contact TerraTrike directly to see if they will sell you one. You can see good pictures of both TerraTrike IPS systems (Rover and Pro model) here: https://www.terratrike.com/product-c...trikes/tandem/
• Vision IPS: Bike Crank Set - Vision IPS Crankset

To set up the captain for IPS, here is one option I found (note: you don't need this unless you also want to be able to coast while the stoker continues pedaling):

• TerraTrike Rover IPS Front: https://www.bikepartners.net/crankse...ips-front.html

There are likely other options out there. I see that Bike Friday and a few other tandem bike makers also offer an IPS system. Just not sure if they sell theirs separately or how much they cost.

To get a taste of IPS another option you could take is to try to find somebody who owns or is selling a Greenline tandem. Or a Greenzone folding tandem.
Both of these tandems (no longer made) came with a basic IPS system (front and rear) already on it.
They apparently sold quite a few of these since I regularly see these pop up on Craigslist or Offerup. At least in my area (SoCal).
Note: these only have the single chainring in back, plus they don't appear to have as easily replaceable/customizable chainrings like the systems above appear to have.

Here are some links to the Greenline tandem plus one for sale near me and one for sale closer to you as an example:
x GreenLine Tandem 7 Spd Shimano Tourney Independent Pedaling Yellow (check out image 5 of 6 for a close up of the cranks)
https://inlandempire.craigslist.org/...399637983.html
https://www.facebook.com/marketplace/item/6259545984086604/?ref=search&referral_code=marketplace_search&referral_story_type=post

Here are some links to the Greenzone folding tandem:
(he shows the IPS system directly)
https://offerup.com/item/detail/225691961

I checked with Greenzone since they are still in business. Although they don't carry the tandems anymore they still have a few sets of the IPS cranks.

They work with standard square taper bottom bracket. They offered to sell me 2 IPS cranks (right side - front and back) for $99. This price does not include left side crank arms.

To get the complete set including matching left side crank arms it would be $149 shipped. You can reach out to: alan@greenzonebikes.com.