Our Calfee tandem purchased in 2011 was built by me with FSA Gossamer triple crankset 50/39/28 chainrings with 10 speed 12-36 cassette.
Front cranks are 170mm and rear 165mm.
I have a SRAM 10 speed shifter for rear and Campy Centaur triple for front.
I have gotten good at shifting the front but still often I mess up a shift which can be hard my wife's legs. Recently the middle chainring is dropping the chain to the small chainring when pedaling on the large rear cog. Looks like the chainring maybe worn and need replacing. Sometimes I get confused which chainring I am on. I have been thinking about upgrading the drive chain for some time. Here is the proposed upgrade:

Appleman tandem crankset 170mm front, 165 mm rear. Nobody else makes this combo.

Shimano GRX 46/30 chain rings, 11 or 12 speed 11-36 cassette.
This would keep the same highest gear, but lower gear would be slightly higher. TA makes a 28T GRX chain ring that might work.
Another option would be Praxis 48/32 but we are old and really need the lower gears. I would need to change the bottom brackets for the 30mm crank spindle.

I already have a pair of Force 11 speed shifters so it would save some money to go 11 speed. I could possibly use eTap but that would cost a whole lot more and I don't mind mechanical.

I figure this is going to cost me $1500 or more. I could simply spend $100 on new chainrings for my current setup. Crankset alone is $1260. It might save a bit of weight.

I think the main benefit here is smoother shifting making for more enjoyment. The Calfee has served us well for its 14 years and I think its time to do this. Thanks for any thoughts / feedback.

Davinci will make you whatever length tandem crankset you want. Price is half of the Appleman. You will likely need bottom brackets as well but you also need that with the appleman set.
Components - da Vinci Designs Tandems

Honestly, I wouldn't drop that money on changing your crankset when all you need is rings. If you want a 2x I'm sure you can do that on the FSA - even with the move to 11 or 12 speed.

If you are looking for more precise gear changes, the electronic shifting will do you much better. I have had a DI2 XTR setup on my road tandem for the last 5 years and couldn't be happier. With the display I know what gear I'm in and I can shift under load without issue. IMHO if you are wanting to improve shifting and thinking about dropping $1500, then etap/AXS and chainrings are my recommendation.

simon

I converted our Santana Sovereign (205) to SRAM eTap AXS (12 speed) and it works flawlessly. 49/39/28 x 10-44. About $1200 for the parts.

Are you saying you are using a triple crank with eTap?

The triple Shimano crankset remains, but I only use the inner and middle chainrings. We spin out at about 35mph, which is more than fine for us. The 28-44 gear has given us the ability to climb anything we've encountered, including one monster hill @ 8,000 ft outside the Grand Canyon (It did hurt though....).

I have an FSA 50-34 tandem stoker's crankset that I'll put on someday, but I haven't seen the need for it yet.

I'm up at the top of Scripps Ranch, so I'd be happy to meet up and show you what I've done.

The Problem with FSA is they do not make a 165 rear crankset which is a must for my stoker. Found out I can order just the rear crankset from Appleman so that will save about $525 and just keep the front crankset as is.
I have Ultegra Di2 on one bike, it is nice but I have SRAM Force 11 speed on another and its not a big difference. I don't really feel a need to go electronic on this.

I might take you up on that. I think this might be doable. I could change the 39T chain ring to 42T and get a 10-36 cassette. Assuming that a 28/42 would shift ok. That would give the same gear range as we currently have.
Which eTap components did you use?

To use a SRAM 12 speed cassette requires an XDR freehub. White Industries does not make an XDR freehub for the Mi6 hub I have.
They do make a hub with XDR called XMRT but it costs $426. Is there any other option here?

Like sdodd above, I think you'd get the biggest improvement by going to electronic shifting. We had two tandems with 3x9 mechanical, but in 2019 we changed to Di2 2x11 on our third tandem and its easily the biggest single improvement in the drivetrain over 25 years of tandeming. Today, if I was doing it, I'd probably opt for 1x12 and make life even simpler.

Ah, I understand. We run 165/150 on our tandem for our short and shorter legs. Davinci Cranks are still half the price you are quoting for appleman - you can buy just stoker or just captain.

If you need shorter cranks, you can also look used on craigslist, FB Marketplace, ebay, etc. Plan on replacing rings on any used crankset but you might find something you really like for a fraction of the price. Tandem parts don't sell quickly.

simon