Small Child's Tricycle.


This traditionally styled children's tricycle was made for a young customer.

It was constructed from steel tube and box section brazed together and fitted with commercial wheels.

 

 

 

 

 

 

 

 

The trike was designed to be as simple as possible to build. All the axles were standard pieces of threaded rod cut to length. Tube bending was kept to a minimum with only the handlebars needing a bend or two, but these could be replaced with commercial items if preferred. No bearings were used, just steel tube on threaded rod, however some of the tubing had to be reamed to get a running fit on the rod.

The saddle and wheels were purchased items.

 

 

 

 

 

 

 

 

 

The wheels were purchased from Machine Mart. The front driving wheel was 200mm and the rear wheels 150mm in diameter. They were heavy duty wheels made from white plastic with solid rubber tyres.

2 of the Tricycle wheels

 

 

 

 

 

 

 

 

Front Axle and Steering

Construction was started at the front of the bike with forks and steering assembly.

The front forks were made from 16mm diameter cold rolled steel tube. The lower 30mm was crushed in the vice to make a flat area. This was then drilled to 14mm with a step drill to give a mounting point for the front axle

 

 

 

 

 

 

 

 

The fork cross pieces were cut from steel plate, marked out and drilled as a matched pair. The 2 larger holes were 16mm and the smaller pivot hole 12mm.

The outside profile was cut and ground to shape.

 

The finished Fork pivots.

 

 

 

 

 

 

 

 

 

 

 

 

The forks and cross pieces were assembled and held in place with threaded rods. Once everything was square the whole assembly was brazed.

The dimension shown had to be large enough to accommodate the radius of the front wheel.

 

 

 

 

 

 

 

 

The Rear Axle

The rear axle was made from a 325mm length of 20mm square tube with a 10mm diameter length of thread rod through the middle. The wheels had 12mm holes in them and so a piece of 12mm pipe was used for the wheels to run on. 

 

 

 

 

 

To hold the threaded rod in the centre of the square tube, some hard wood bushes were made to be a push fit in each end of the tube.

 

Push fit wooden bush

 

Drilled 10mm

 

The wooden bush was then drilled to take the 10mm threaded rod.

 

 

 

 

 

 

 

 

Rear axle detail

The rear wheels were 33.5mm thick and so a piece of 12mm tube was cut to a length of 34mm to allow the wheel to turn once the nuts were tightened up

The tube was fitted to the threaded rod with a washer both sides and then a nut on the outside. This was done both ends and then the nuts tightened to clamp the whole lot together.

 

 

 

 

 

 

 

 

This CAD sketch explains the Rear wheel bearing set- up.

The only important thing was that the 12mm bearing tube was slightly longer than the width of the wheel hub, so that the wheel could still turn with the nuts fully tightened.

Click to read

 

 

 

 

 

 

 

 

The Frame

The frame was a straight length of 20mm square tube.

A hole was drilled in one end to take the head-stock tube. This was a 14mm diameter piece of tube which would take a 12mm bolt. The angle of this hole set the trail of the trike and can be varied to suit. This particular trike had a 10 angle at the head-stock to give a 10mm trail.

Hole being finish with a 14mm milling cutter.

 

 

 

 

 

 

 

 

A piece of 14mm steel tube was turned to be a snug fit between the steering webs as shown below.

It was then brazed in place in the frame tube.

Steering pivot before brazing.

 

 

 

 

 

 

 

 

The frame and forks were joined with a pivot bolt and the wheels were temporarily bolted in place so that the angle between the rear axle and frame could be measured.

This angled cut is optional and only needed if you want to keep the rear axle tube flat to fit a buddy board. If this is not needed then a simple butt joint can be used.

Once this angle had been measured a notch was cut on the milling machine.

 

 

 

 

 

 

 

 

The frame and rear axle were brazed together ensuring that the two were square and that the rear axle was centred about the frame. Absolute accuracy is not essential here as one of the nice things about a trike is that a non-square rear axle won't affect performance.

The rear axle brazed to the frame.

 

 

 

 

 

 

 

 

 

 

The tricycle parts so far.

 

 

 

 

 

 

 

 

 

 

Pedals and Crank

The main axle was a length of 12mm threaded rod cut to length. The drive from the pedals to the wheel was transferred using nuts to grip both the wheel and the pedal cranks. 

 

 

 

 

 

 

 

 

To help the nuts grip the wheel some lock washers were used. These were made by taking some plain washers and punching marks on both sides as shown

 

 

 

 

 

 

 

 

With the forks secured in the vice the rod was passed through and nuts, washers and wheel and tightened very firmly so it wouldn't slip.

 

 

 

 

 

 

 

 

Bearings were cut from 14mm tube which was reamed to have a 12mm hole in the centre. This was then pushed into the whole in each fork and drifted into place until the side movement of the axle was minimised.

Drifting bearings into place

 

 

 

 

 

 

 

 

Two pedal cranks were cut from 2mm thick flat plate. The distance between the hole centres was 50mm. One hole was drilled 12mm to fit the axle and the other tapped to take the pedal pivot.

A length of 10mm threaded rod was fitted and brazed into place in each of the tapped holes. The brazing was kept to the rear of the spindle so that it wouldn't affect the free running of the pedals.

 

 

 

 

 

 

 

 

Pedals were cut from hardwood cut and sanded to shape. Some gripping strips were cut on the band saw.

The pedal was then drilled to take a length of 12mm tube. This tube was reamed with a 10mm reamer to fit neatly on the threaded rod. Each pedal was secured with a lock nut which was made by sawing a 10mm nut halfway through and then squashing the cut together so that it gripped the thread.

Pedal on crank.

 

 

 

 

 

 

 

 

Finally the pedals were set at 180 and clamped the to front axle using a nut on each side.

 

 

 

 

 

 

 

 

Fitting the Seat.

The seat was a commercial item. And was secured to the frame with a clamp to allow the position to be adjusted.

The clamp was bent around an off cut of 20mm square tube to be a neat fit and then drilled right through to take a 10mm bolt.

 

 

 

 

 

 

 

 

The seat required a 22mm piece of tube to fit it in place, so a 22mm piece of plumbing copper was used. To ensure this was mounted vertically the clamp was placed on the assembled frame and the angle measured. Then the pipe was cut at the same angle and brazed on to the seat post base.

The seat was angle adjustable via the standard clamp, so the angle was not critical,

 

 

 

 

 

 

 

 

Handlebars

A size check with the young customer showed that the handlebars needed to be further forward. The top of the forks were bent forward to try and get the reach correct but they wouldn't bend far enough without creasing. So they were sawn off, the inside of the forked was then reamed out to 14mm so that a piece of 14mm steel pipe was a sliding fit.

 

 

 

 

 

 

 

 

Two 14mm diameter pieces of pipe were bent forward and a third piece was brazed in place across them to form the handlebars. This set up also gave the advantage that handlebars were now height adjustable.

To finish some grips were made from old car water hose and finished with a wooden bung to match the pedals.

 

 

 

 

 

 

 

 

 

Tricycle construction finished, just paint needed to complete.

   

Road test update.

After a few journeys some things became apparent.

  • Initially the customer preferred to scoot the trike rather than pedal. For this reason, being able to remove the pedals and cranks was useful.
  • Once the pedals were re-attached it was made easier to ride by machining the crank pedal nuts to reduce their width by 50%. This saved the rider's heels getting caught on them and shortened the overall length of the axle rod.
  • Having the handlebars curved forward ahead of the front wheel was useful when towing the tricycle. It allowed it to be towed with or without the rider and be steered by the rope.

A few weeks later a simple trailer was made from wooden cuts and 2 more 150mm wheels. This proved very popular and added another dimension to the trike.

Tricycle and Trailer.

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