Larry's Kid's Trike

     First, pardon the blurry pictures.

     Larry built this trike after seeing the KMX trike.  All his trikes are very similar to this style and the only difference being that this was built on a smaller scale than his "normal" trikes.  The frame is standard 1/16" mild steel.  The main frame and cross memebr is 1½" box and the chain stays are ½" x 1¼" box.  The chain stays are first welded to a piece of 1" steel pipe, and then the pipe is welded to the end of the main backbone.  Larry used the pipe in between the chain stays and the frame because the round pipe is more resistant to twisting than square stock.

     The front wheel hubs are custom machined by Larry's friend Roger and have ½" grade 5 bolts for axles.  The steering linkage is ¼" stainless rod that has been threaded at the ends.  The king pin bushings are custom machined by Larry out of high density plastic and use ½" bolts as kingpins.  Larry also machined a custom aluminum flag holder.  The trike frame is very strong as evidenced by Larry riding the trike himself and aside from his 200lb+ frame possibly causing the front wheels a little grief, the rest of the trike handled him just fine.

     The seat is made of a section of 3/4" EMT and is covered with a pool noodle that is split down one side, and slid over the tubing.  The back of the seat is unsupported, but rigid.  The bottom of the seat has two lengths of 3/4" steel box tube that connect the seat rails together.  The box tubing has tabs welded onto them, and the tabs are bolted to the main backbone.  Black mesh (for catamaran trampolines) is used for the seat bottom section and is laced underneath.

     The trike has fairly high gearing for its "low" gear, but my 6 year old daughter had no problem riding up hills with it and in fact, she quite enjoyed how fast she could go on it but the trike never even hinted at raising the inside wheel on a turn.  She was even happier when she realized she could change gears and go faster still.  :) Even though the trike has front caliper brakes, my daughter's small hands were still able to reach the long levers, which gave excellent leverage for her to stop the trike in very short order.  I am very impressed with the brake performance and had no worries about my daughter's safety while riding.

     Larry used a 38 tooth chainring on a one piece crank with ~150mm cranks.  The boom has a little over 6" of adjustment (and more with a few chain links added) and is clamped in position by using 2 short seat skewers as pictured above.  The boom gave exactly zero hint of any movement after the skewers were tightened.  The front derailleur post was added possibly with "future development" in mind . . . like maybe a 108 tooth chainring??  Sweeeeet!  :)

Above is a picture comparing the trike's size to my Mk 3.

Specs:

     Larry indicated that he wanted to repaint it to silver, do a little tweaking of the front wheel hubs and change the method of fastening the seat's back so he wouldn't have to cut the pool noodle.   In the mean time though, I think it is avery cool little trike and is a further inspiration for me to carry on with my own design for a kid's trike.

The trike with its final silver paint job, black plastic spoked wheels and new rear derailleur.  Very nice :)

     I bought 4 of the 12" plastic spoked wheels from Northerntool.com with the intent of trying them on a kid's trike version of my own.  The bearing are pretty low grade radial bearings and in my experience, not worth even attempting to use them as is.  I popped them out to see what the inside of the wheel hub looked like and took some measurements.

     I went to my friendly neighbourhood metal-dude and bought an 8" long by 3" dia piece of 6061 Al and machined myself some hub inserts that could hold a ½" precision bearing.  The hub inserts are a little oversize so they press in tight to the wheel, and slightly undersize so the bearings need to be pressed in.  I stepped them down to match the inside contours of the plastic hub with the intent that they make maximum contact with the wheel hub for maximum support and minimum maintenance.

     In the pictures above, you can see the ½" bearing already pressed into the hub insert.  The side with the smaller diameter steps is the side that slides into the 12" wheel's hub, and the middle flange (the largest dia one) still has to receive 3 #10 holes at 120 degree intervals.  The three holes will get long #10 stainless steel Allen screws that go through to the other hub insert and when tightened, sqeeze the two hub inserts and wheel hub together.

     The outside diameter of the hub insert is slightly bigger than the outside diameter of the plastic hub so that there is maximum contact and support by the edges of the hub ends.

     Oblique view of same.  Ready to have the through-bolt holes drilled.  I made a small locating jig using the last little bit of 3" round stock that was left over.  The inserts go into the jig face down and all the hub inserts get their #10 holes drilled in exactly the same spot to aid in alignment.  Based on advice from Larry (who's a vet at custom hubs and hub inserts) I only used 3 bolts per wheel.

     Here is a picture comparing the size of my modified 12" wheels with the 16" front wheels on Larry's trike and the 3 through-holes are drilled and bolted . . . finally.  The 12" wheels are rated at 125lbs each but look pretty tiny even when compared to a 16".  After I build the rest of the trike, I think I'll likely gravitate toward 16" wheels like Larry did.  While the wheels are rated for 125lbs radial loading, I'm not sure what kind of load they could take laterally so I'll err on the side of caution and go to 16" - likely spoked, and not any more mags.

     I will post full info on my kids' trike on its own page when it is complete.  I hope it works as well as Larry's does.  More to follow . . .

Larry's Kid's Trike 2

     Another fine creation by Larry.  This trike is made from all round steel tube with the seat being 3/4", the chainstays being 1" and the backbone and cross member are 1 1/2".  The boom is adjustable and made from 1 1/4" steel tube.  It has 16" front wheels and a 20" rear.

     It has a mesh seat, direct steering, dual front 160mm disc brakes, 5 spoke poly wheels with custom machined front hubs, locking brake levers, Delrin steering bushings and a 7 speed cluster.

     A nice little trike, about the same size as his first one.  More details on weight and measurements as I get them.

Update - 1 Oct 2007

     I finally got the opportunity, or took the opportunity, to take some measurements of Larry's little trike.  Compared to the one I just finishde for my daughter, it's still a smaller, tighter little trike.