LastKraftWagen

Still working out the details on a custom frame build and I'm hoping for some help with telescopic seat tubes (like the CoMo periscope). Because I use a wide variety of pilots, I'm considering this for the front cockpit. What I can't seem to find (without emailing a builder here then taking their data to another builder...just feels better if I ask a third, private party) is the dimensions and how to describe them through a significant language barrier.

What I'm hoping to find out is generally what range of height riders do these setups accommodate, and what lengths are the seat tubes and extensions?

Appreciate it.

qspencer

I have a Bike Friday tandem. The seat tubes are both 12 inches tall. The middle section of the telescoping seatpost for the pilot (me) has 8 inches sticking out, and I don't remember how much is inside the seat tube. The regular seatpost also has a good deal exposed (I'm 6 feet 3 inches). The 12 inch seat tube is short enough that with all of the seatposts collapsed, we were able to accommodate my son at age 4. I've only seen pictures of the Co-Motion Periscope, but they look to me like the rear seatpost is probably about 12 inches, and the front seatpost is probably in the range of 15-16 inches. Maybe a Periscope owner here can confirm that. For reference, my kids (between 4 and 5 feet tall) now easily fit on the rear of our other Raleigh tandem, which has a stoker seat tube of 17 inches. I think a 16 inch seat tube in the captains position could be pilotable by a 5 foot tall rider.

Dean V

The compact style frames like C'dale have a lot of seat post out for the captain and stoker. The limiting factor for a variety of captain sizes won't be the seat post but the reach and drop adjustment required for the handlebars.

zonatandem

. . .as for reach adjustment . . . there is a solution for that also.
Co-Mo can get an adjustable *pilot* stem for you. It adjust up and down + in and out (similar to an adjustable stoker stem).
The Co-Mo seatpost-within-a-seatpost will easily accommodate a pilot of 6'3 down to a 5' pilot.

LastKraftWagen

With the Burley I can currently get nearly 13cm of horizontal seat movement (measured nose to stem cap bolt) depending on saddle and seat post, and about 10.5cm vertical stem movement using a Delta Cycle raiser, plus I have a variety of stems ranging 70-140mm [ish, measured with a tape graduated to 1/2"), and flipping them allows for a bit more vertical adjustment. The problem with the Burley is the 22" (or 22.5" depending on which day I take the tape to it) seat tube...I can fit someone down to about 5'8" if I use the really skinny seat and 170mm cranks. I've fit up to about 6'2" - 6'4" (never really asked, but dude was tall) using a 400mm post. The stoker seat tube is about 19" and fitted to me (5'9") there is about 6" of post showing. I'm just perplexed (over-thinking) over tube length and acceptable extension length to describe to the builder (again, I don't feel comfortable sending another builder's pics and saying "build like this...").

I know neither extreme is good for handling, but most of the rides out here are lacking in turns and the TTs are mostly out and back, and the extremes are more the exceptions rather than the norms, but I'm trying to fit as many pilots as possible.

I've considered the Co-Mo adjustable stem (through Tandems East I think), but haven't gotten around to ordering one yet.

Eh, OTOH it will probably all wash out and I'll end up with something less "this is what I want" and more "this is what really makes sense."

Thank you all.