Three dollar crank forward

A couple months

back I stopped at a garage sale that had a couple mountain bikes leaning against a tree. They had no prices posted--one was a dimestore clunker with 24" wheels and one was an old Trek 26" mountain bike. I got brave and asked how much for the Trek and the lady said $6 would buy both but I managed to take home only Trek for $3.00. I figured the bike would be in sorry shape as rusty water ran out of the frame when I loaded it into my van but when I tore things down I found all the bearings in good shape, needing only a good lube job. The shifters seemed to work pretty slick--they are a 3x7 trigger shift system and all rust cleaned off pretty easy. The tires have no noticable wear, so I decided to turn this bike into a crank forward cruiser by moving the rear wheel and seat back about 7 inches. Most of the added tubing is .035w 4130 Cro-mo 1" OD from Aircraft Spruce http://www.aircraftspruce.com/index.html and Airparts http://www.airpartsinc.com/ .
The seatpost is 1" square 1/8" wall aluminum tube.

Total investment is still under $100 with brazing gas and tubing counted. The finished bike weighs about 30 lbs and is a great ride. I put about 60 miles on in the first week or so even though our daytime high temps have seldom exceeded the freezing point here in KC. I'll tear the bike down and paint the bare parts black to match the rest as soon as the next snowstorm forces me to stay inside for a couple days.

Update 12/26/2010: I finished painting and reassembling the bike today and added the 2 new pictures above. I kept the old paint on the front half of the frame and just repainted the back half. I also added 1.5" in length to the handle bar ends by making some bar plugs out of dowel rod and aluminum tubing.

Motor bike idler re-design

The idler kit for these cheap motorbike kits is pretty lame. Notice the clamp that grabs the chainstay and the slot the idler pully has to move up to tension the chain. This setup seems to let the chain loosen up after about 5 minutes of riding time. The nylon pulley is probably not nearly as satisfactory as an idler sprocket would be but that upgrade will have to wait for later. My current effort has been centered around the mounting and adjustment portions of the idler system.

Here is what I came up with. The new unit uses a swing arm pivoted from the bottom rather than a slot for moving the pully against the chain. Note the welded on tab on the chainstay and on the seatstay where an adjustment screw can be hand tightend and then locked with a wingnut to pull the chain into the desired tension. I'm thinking that having the tensioner setable without tools will enable the chain to be removed from the sprocket out on the road, making the bike much easier to roll back home should the motor quit (hope for the best, plan for the worst).

4 stroke bike

This project came about when my son sent me home with a bike motor kit and asked me to turn it into a motorbike. The motor is a 48cc 4-cycle with centrifugal automatic clutch. A friend gave me an old Phillips 3 speed frame and I had a heavy duty fork in the shop as well as some steel 26" wheels and some extra tires. The motor is fairly smooth and quiet and pulls up hills pretty good, which is fortunate as there was not room enough for pedals to be installed. The gearbox generates some whine and the chain idler will need some improvement but the finished product shows promise as a fun little motor bike.

Home built AMF Crank Forward

I wanted to try building an inexpensive crank forward so I started with an old AMF single speed bike that had little wear on in but needed some TLC to be ready to ride. I straightened the fork a little and trued up the wheels and adjusted everything to get the bike rideable and then tore it down and cut up the frame and added 4" of length to the chain stays and put in a fatter seat tube and seat post at a more laid back angle and added a piece of tubing across the top of the frame to stiffen it. I built a larger saddle and put on some pull back handlebars to give the crank forward type comfort. I reduced the gearing to about 50" by replacing the front sprocket with a 36 tooth sprocket. I'm too tall to fit on this bike properly but it is much more pleasant to ride than the original was.

Cost of this project was probably under $40 counting paint and brazing supplies.

cheap bike light

LED lights have popped up all over the market place and I recently saw some very nifty little flashlights at Advance Auto stores for $2.50 each. These guys come with 3 AAA penlight batteries and put out an amazing amount of light. I've been thinking these would make nice bike lights if you could come up with a simple and light weight means to attach them to your bicycle. I prefer a system that allows the light to be easily attached and removed and still allow the light to be carried in your pocket or bike bag.

I decided to make a saddle to attach to the light that would let it sit on the handle bar and use rubber bands to hold the light to the bars.

The saddle is made from a couple scraps of 1" diameter thinwall bike tubing. I used a section about 1/2" long and cut that ring of steel into thirds. I welded 2 of these little arcs of steel together using my mig welder mostly because I wanted to practice using the welder. I think you could use aluminum tubing from lawn chairs or PVC pipe or most any material and glue the pieces back to back with epoxy glue such as JB Weld. The joint strength here probably doesn't need to be very high as this saddle just keeps the light pointing straight ahead. When the saddle was welded together I glued one side of it to the flashlight using double sided tape and also used double sided tape to attach a little rectangle of inner tube rubber to the other surface to give padding and traction where the saddle contacts the bars.

Here is a shot of the light strapped onto the bars using a couple small rubber bands cut from inner tube.

Crank Forward #1 handlebar/gooseneck revision

My home built collapsable crank forward bike has been proving to be very comfortable and enjoyable riding over the last couple years and over 2000 miles. One area of improvement I wanted to explore was abilitly to stand while pedaling. My handlebar and gooseneck setup gave good comfort and stability but there was not sufficient clearance for my knees to clear the bars while standing on the pedals (see before picture above). I had a pair of Rans B38 bars laying around http://www.shoprans.com/proddetail.asp?prod=BPHB0038 and I decided these could be located for good comfort and standing ability if they had a tall riser with very little forward offset, much like Rans uses on their Crank Forward bikes. The resulting home built gooseneck was made from brazing some 1-1/4" steel bike tubing onto a lower section of steel goosenck and then gluing in a piece from the top of a heavy duty aluminum gooseneck at the upper end using JB Weld and a couple 1/4" set screws for added security. The result shows a lot of promise from what testing I've been able to do so far. I'll do more field testing once the half foot of snow we have here in KC goes away.