Building a better Tall Bike

Step 4 Attach top rear triangle to bottom bike's seatpost

So now, take your steel seatpost for your botttom bike, remove the saddle from it, and chop the tip off. now cut a slot in the end to fit the chainstay bridge of your top bike. error on the tight side so you can just stick it on there and let it hang while aligning it.

Now you'll want it nice and centered, parallel to your seat tube, use a ruller to line them up ,like in the second picture. To make sure it's lined up the other way, and centered in the middle of the chainstay bridgeyou can put two straight eges on each side of the BB shell.

Now tack it, i used a flux core welder for tacking, MIG is way better, but at this time i only have gas for stainless, so i'm tacking with flux core and fillet brazing to finish. Tack everything before you weld anything, and you will be much happier.

Once you've got your seatpost tacked, doublechecked for alignment, and tacked some more, drop the post into your bottom bike.

In hindsight, you could also do this by cutting the seatpost at an angle, welding it to a plate, such as a kickstand plate, tahen welding the plate to the bottom of the chainstays, this would allow you to move the top triangle lower and further froward