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Once More Into The Breach --- Scratch-Built 1/72 Spoke Wheels Again

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I posted up an earlier run at this a while back:




Even as I was posting it, possible improvements to methods were occurring to me. I have gone ahead and implemented these, with some success. I made seven spoke wheels (with 7mm/in scale 20" outer diameter) this past weekend, at the rate of about one and a half hours per wheel. I think I have gotten this to a true 'production' state. The completed wheels I think are much improved, easier to handle in the finishing stages, and 'finer' in the size of their components.

Here are the jigs and tools used in making and assembling the wheels.




The jig at the left is for weaving the spokes onto a wheel half. It finally occurred to me to have wife print out something with eight points. However, the eight points, probably owing to distortion in being blown-up from a small original, do not quite align correctly. On this, the notches at the points were adjusted till all the lines crossed precisely over the center dot before the central spacer, of 0.75mm rod, was placed.

The jig in the center is to hold the wheel halves aligned when they are attached to the axle/spacer. It began as a weaving jig, but failed in that because I had assumed the points were aligned truly, so that it produced off-center spokes. The four rods of 1mm rod around what was originally a centralizing collar hold the alignment. The center was cut out to give a good view of how the spokes were lining up.

The item at the right is the tool for fastening the wheel halves together. Its base is an earlier weaving jig ready to hand for the purpose. A ring off the tubing stock is in the center. Four long pieces of 1.5mm rod are attached and form a guide. The wheel halves, joined already to the axle/spacer, are placed inside. A length of tube then presses down, guided by the rods, and applies uniform pressure to both wheel halves, while the rods preserve external alignment. This item also has the secondary function of holding the wheel halves while their mating surfaces are marked for notching.

Here are the pieces employed....




At the top are two raw wheel halves freshly cut from the tube. Beneath these, at the left is a wheel half tinned down and marked for notching, and at the right is a notched wheel half ready to receive spokes. I had tried notching in earlier experiments, but discarded it as it weakened the wheel halves and they bent in assembly, but that was in the early going, and the assembly tool now removes that difficulty.

On the near right is a finished axle/spacer, and on the far right is the 'raw' item. A hole is put in a square of 0.75mm sheet, a length of 0.75 rod is put through and fastened. The square is clipped and sanded down till round, and while of greater diameter than the rod, not greatly so. The rod is then trimmed down. It is important one end be longer. Both must be sanded to a bit of a point.




On the left is a notched wheel with its spokes. The spokes, pressed into the notches, work to center the wheel half. These are glued in, being sure the spokes are deep in the notch, and the notch filled above them with CA gel. The notches are put in with a knife-edge needle file. Once the wheel half is cut off the weaving jig, an the excess trimmed, the mating surface can be sanded flat with a fine grit sanding stick. The notches fix the spokes firmly enough in place to allow this it very little risk of disturbance. On the right is a wheel half with spokes trimmed, and the wheel's axle/spacer affixed. The short end goes into the lower wheel half.




Here is the second wheel half also attached to the axle/spacer, correctly aligned.




The longer end of the axle/spacer allows glue to be applied after the second wheel half s aligned, before it is pressed down onto the 'step' of the axle/spreader.




Here are the joined wheel halves in the assembly tool. Glue (CA gel) is applied in a manner which avoids the rods. The length of tube is pressed down; it can be held in place between thumb and middle finger, or placed on the bench and pressed down. After a ten count I apply liquid patience, and continue to hold for a slow sixty-count. A Once the 'plunger' is removed, a knife-point will lift the wheel off the base, and it can be lifted out readily.




One the left is a wheel fresh out of the assembly tool; on the right is a finished wheel.

Finishing consists of clipping the excess off the axle/spacer, and dressing it down with a 'swizzle-stick' sanding stick. Examine the outer rim for un-glued seam, and apply a bit of CA gel smoothed down with a tooth-pick. Sand the outer rim down smooth. Then You can sand down the sides of the tire with a heavy grit sanding stick, keeping it tilted slightly away from the center and the spokes. Though you should not hold the wheel in a death grip, you can hold the center while you do this with reasonable safety. Sand down close to the 'points' of the notches (the dark color of the set CA gel will be visible). Finally, knock down the edges of the outer rim to give the thing a bit of rounding, and end with some smoothing from a fine-grit sanding stick.

Here are the weekend's production....




The penny is for scale, and the wheel from an Eduard N.17 kit shows how how undersized these 20" wheels are to the more usual items. It would not be difficult to scale this up to produce wheels of the diameter of that kit piece. At that size, a dodecagon rather than an octagon might be employed, though an octagon would certainly do.

At any rate three wheels will be selected from those pictured here for incorporation into a scratch-built model of 'El Somora'....




I will leave you with the contents of the 'swear jar', all the various earlier wheels and attempted wheels which have gone before....



Edited by Old Man
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On 7/13/2017 at 0:45 PM, Beard said:

Making a jig to enable one to scratch-build something is proper modelling. I doff my hat to you, and will go back to assembling kits.


On 7/13/2017 at 1:26 PM, celt said:



Thanks a lot, guys. This is kind of a 'Holy Grail' thing for me, there are a lot of subjects I would like to do that would require spoke wheels, albeit larger ones. I feel confident I have the method down for the sies I need in my scale with the materials available.

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19 hours ago, Corsairfoxfouruncle said:

:o time to be awestruck !!! You have entirely to much patience.


I don't know if it's patience so much a sheer bloody-minded persistence, I don't like to leave go a thing I have started.

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