Child's Tricycle.


This project was a small tricycle based on a child's 12" wheeled bicycle but with a modified frame to make a tricycle with 2 wheels at the front.

 

 

 

 

 

 

 

 

The donor bike was a small child's 2 wheeled bike from a junk shop. It had 12" wheels and a standard 2-triangle frame.

The brakes were broken, the tyres flat and the seat damaged, but the frame was good which was all that was required for this project.

Some steel from the frame of an old ladies' bike was also used, this frame came from the local scrap yard.

The Donor Bikes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The frame was cut at cross bar and the bottom bracket to leave the rear triangle of the frame intact.

Frame before cutting

Frame cut in half

 

 

 

 

 

 

 

 

Originally it was planned to add 2 horizontal bars to hold the steering pivot in place, but after brazing the first one in place it was more rigid than expected and so just one bar was used. The bar was taken from the ladies' bicycle.

This photo shows the first joint being tested for strength.

Frame under load test

 

 

 

 

 

 

 

 

Next the steering pivot was added. This was the original head-stock from the donor bike. Care was taken to ensure that both the cross bar and steering pivot were accurately aligned otherwise the tricycle could end up being difficult to control.

The length of the steering tube was also shortened slightly to give a lower profile to the whole steering mechanism, but it was only shortened within the length of thread available on the bike forks to avoid any need to extend this thread.

Steering pivot in place

 

 

 

 

 

 

 

 

The front beam axle was made from some 20mm square tube, cut to a length of 400mm.

The front forks from the original bike were cut off as shown below, and slotted to take the beam axle. A steel pin was located through the brake mounting hole to secure things before brazing the assembly together.

Front axle locating hole

 

 

 

 

 

 

 

 

Each end of the square tube had a piece of metal brazed into it which was tapped to take the front wheel axles. The axles on this particular bike were 3/8th inch x 32tpi which was a standard BCT (British Cycle Thread)

 

 

 

 

 

 

 

 

The front cargo deck was made from plywood, but it was also integral to the bike's steering, so strength was important.

The base was an 18mm piece of plywood which was drilled with a 25mm hole to locate on the top of the fork tube. The front edge was cut at 30 and the rear at 10. The width of the base was 400mm, less the thickness of the 2 sides.

Load Deck

 

 

 

 

 

 

 

 

Underneath the load deck two support ribs were added to not only distribute weight onto the axle but also to transfer steering forces from the handle bars to the front wheels. These were made from 12m plywood cut as shown.

 

The slots in the lower edge of the ribs were a tight fit on the axle. The height of the ribs was cut so that the top edge was level with the steering nut on the centre pivot.

 

This second photo here, shows how the load deck, ribs and axle all fitted together.

Load deck support ribs

 

 

 

 

 

 

 

 

The sides of the load deck were cut to a suitable profile and glued and screwed in place.

 

 

 

 

 

 

 

 

The handlebars from the donor bike were drilled to accept 2x 6mm bolts.

A reinforcing piece of plywood was screwed the to back panel of the cargo area to allow for vertical adjustment of the bars.

 

 

 

 

 

 

 

 

The bike was equip with a single rear brake. This was a standard caliper brake but the cable was routed via the front pivot so that the steering wasn't affected by the cable. The cable was secured to the bike frame using cable ties (zip-ties)

Rear brake and cable.

 

 

Image of brake cable looping round steering pivot.

 

 

To finish the frame was give a coat of black enamel paint and a rear mud guard and reflector were fitted.

Click to enlarge

Click to enlarge

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