So, I've been playing around with the tag-along style attachment on our Bromptons:
Although it's certainly fun, I'm getting ready for some light travel to the bay area and wanted to do more with less. I need to carry less stuff and I don't want to risk getting the whole family mowed down while riding in unfamiliar territory.
With some judicious googling, I found the IT Chair. Aside from the cost, it looks to be a set height. Probably requires too tall a position for my wife.
I also found the DIY IT Chair by some guy in the Philippines, so I figure I can go the DIY route.
I made two of these (one for each bike) so that our family of 4 can enjoy the SF Bay Trail once we get there.
I started off with the trailer hitch and saddle from the WeeRide Co-Pilot tag-along attachment bike. Then a 25.4mm x 12" steel seatpost, and a mtb stem I had laying around. Bought some aluminum flat from Lowes. I used something called Alumiweld to braze the shaped aluminum flat to the stem. It was tricky cutting the stem at the correct angle, since it required lots of fitting. As for protecting my frame, I cut up a piece of washing machine drain hose. The final piece was foot pegs for the kids. I was all ready to make a set, but was apprehensive about strapping stuff to my Brompton frame. Then the perfect solution was staring right back at me, in the form of the S luggage frame. My kid can rest his feet on the S-Frame.
My kids are 6 and 4 years old, and neither of them over 45 pounds. Initial test rides are good. Everyone's happy.
Here it is, more or less (still needs to be tightened up to this bike, etc).