4" Foster Wheel assembly at Bailey Steam Engineering

 

Introduction

Wheel building can be quite a heavy task. Some model engineers like to get some help with the wheel assembly. This information is an example of a customer who had pre-machined the wheel hubs, prepared the spokes ready for assembly and infact had done a lot of the work to getting a set of wheels. The task detailed below is for the wheel rim preparation and wheel assembly.

  • Wheel Rim preparation

Rolled sections were obtained from a commercial section rolling company. Rolling flat on edge requires a special machine and a skilled operator. The sections require welding and dressing before the inner rings are welded in to the wheel cylinders. To ensure a strong wheel the tee ring is ground to a combined angle of 60 degrees on both sides. A small flat is left on the inside to maintain the radius. I usually clamp the tee section in the vice and weld the inner and outer edges first to keep the rolled section in line. The main weld are best welded last!

Tee ring weld photo (inner & outer)

After welding the welds are ground back to the tee surface and inspected for finish. Any irregularities are filled with weld and ground off to give a clean finish. A final finish with a file adds a nice blending radii with the rest of the ring.

The wheel outer rolling is also treated in the same fashion. Again the aim here is to get a good strong butted weld that will not be visiable after the wheel is complete.

 

Wheel Outer Rolling tack welded only as delivered from Section benders

A tee ring is then placed inside the outer rolling and set to the correct depth. The rim is positioned by adding small tack welds both on the inside and the outside until the tee is supported in the correct position. As you may be aware welding pulls the parts close together as it cools in the same fashion as hot riveting. An uneven pull will cause distortion. If this weld tacking procedure is not done the tee section may pull during welding and not be perpendicular to the rim.

Tee ring placed in rim for welding

The main welding is done in a similar fashion. Do short welds of about two inches long both inside and outside the tee rings alternatively. Rotate the rims 180 degrees and do the next runs opposite the last. This helps to distrubute the weld pull and heat stress evenly and keep the risk of distortion low. Some builders try and get a weld radius to represent the radii in the finished rim. I prefer to use a smaller radii weld (dressed too if required) then fill the welds to produce a nice acurate radii.

Filler applied to the welded tee rings

The filler is best put on with your finger a small bit at a time. If the rims are still warm the filler is set quickly and you are able to start sanding. I use a coarse grade of paper to remove the filler that squidged out past the finger on application and to make the radii. Adding a a small amount of filler may be required after to fill any small irregularities. When the rim is finished to satisfaction a coat of primer is a must to prevent the posibility of rust.

Front rim, Welded, Filled and ready for assembly

  • Spoke preparation

Cutting out spokes can be a labourious task. I prefer to use laser cut spokes. Some builders leave the laser cut finish on the spokes and this is quite good. A better finish can be obtained if the cut edge is dressed. A belt sander is the best method of removing the cut finish because it can be quite hard. Always add a small chamfer to the spoke edges and indeed any edges that will be painted because it is hard to get a good thickness of paint on a sharp corner. I have not detailed the manufacturing of the hubs in this document but it is worth ensuring the spokes are a good fit into the hub spoke slots after dressing to make the wheel strong! Front spokes can be pre-drilled before assembly because of the single tee ring. Rear spokes have to be drilled on assembly through a drilling jig because they usually fit on the inside of the tee.

One corner of the spoke palm end will need a large radius to allow it to fit into the rim radius. I have included a section of an original Fowler works drawing as an example of how it was done!

Add copy of spoke drawing from reading

  • The wheel building Jig

Wheel building can be done on a wooden board, I use a 1/2" thick steel plate for my assembly jig. Angle brackets are bolted to the plate at 90 degree positions. This angle brackets have adjustable position clamps to allow easy centring of the hub to the rim. The hub is positioned in the centre of the jig on a mandrin that is secure from below. The mandril is perpendicular to the plate surface.

Wheel Assembly plate with angle and centre adjuster

  • Wheel assembly

The hub is fitted on the centre mandril with a spacer to position the hub to the correct position within the rim. The rim is placed on to the jig and centred with a tape measure. The adjusters are lightly tightened to hold the rim. A pointer is then attached to the hub with an engineers clamp. This pointer is adjusted to inspect the centring of the hub to the rim. Carefull adjustment of the centring screws will allow the hub to be positioned acurately within the hub. The pointer is then adjusted to check the hub to outer flange run-out. This can be corrected if required by adding thin packing below the rim in the required position. The centring has to be re-checked if packing is added! Finally lock the adjusters in position.

Piece of bent metal used to centre the wheel and check for wobble

The palm end of the spoke is bent to allow the spoke to fit flat against the tee ring in its correct position and just touch the edge of the hub at the bottom of the slot that has bee pre-cut.

Bending spokes, note the try square to set the spoke square before bending

Mark the edge of the hub on the spoke. This end is then bent to the correct angle. I use a small fly press (above) to bend the spokes. Get them square to the tool and you get parrallel bends. Another way of reducing unknown distortion. Mark the spoke length to cut off the excess off but leave it longer than required by around 1/16" of an inch. File the end of the spoke to match it to the slot radius. I believe method supports the spoke (as well as the fastner) and makes a really strong wheel.

Spokes fitted into the hub and drilled

Finally trimming the length until the palm end is in the correct position. Finall check the bending is correct by pressing the spoke each end. If the spoke lifts out of the hub slot or there is a gap below then it is best to correct this and get a good alignment. The more accurate the spoke is laid on the rim and in the slot the better. This will allow an assembly that is not being pulled by uneven stress when the wheel is rivet or fastened into the hub.

Using the drilling jig

Completed wheel

Secure the hub end of the spoke with counter sunk screws and pull them down tightly. Clamp the spokes to the tee ring with as many clamps as possible. Then turn the wheel over. Drill the palm end through if it is a front wheel or through a drilling jig for the rear wheels. A drilling jig is required here because the tee ring has to be drilled in the correct position to line up with the spoke. This is also held with a clamp or Mole grips!

Well the front wheels are a little easier to build on most models. On the Foster both spokes are mounted on the outer edge of the tee ring. This means the rear spokes have to bend a lot to get where they need to go. Getting the length correct can be tedious. I have added a couple of views if the completed wheels.

Front Wheel in Build and Complete

Complete set of wheels

Well nearly, they need riviting and rubber tyres fitting. Still the job is nearing completion at last.

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