Tuesday, October 11, 2016

A Toy Eighteen Wheeler

I have an old Ryobi project book that has quite a nice toy truck in it. The book is Vol. 3, No. 1, February 2001. Here's the cover.

And here's the truck.

I like that truck. I think it's a fine truck.

I'm going to depart from the text's instructions in several ways, though.
  • The text makes much of making your own wheels with a circle-cutter.[1] The prospect doesn't really interest me, especially not when Lee Valley has exquisite ready-made hardwood wheels for a reasonable price. (I'll be using the 1 1/2" x 1/2" version of item 'A' -- Cat. No. 41K01.66.) Here's a view of Lee Valley's wheels, along with axles that I've made for them.

  • The text would have you build the truck using maple stock throughout. That's a nice choice of material, but maple is costly. I'll be building this truck from whatever odds and ends I can scrounge up. I splurged a bit on the wheels, so I'll make up for that on the rest of the material.
  • The text appears to have the wheels fixed to the axles, with the axles rotating within oversize holes through the chassis. I'm going to do the opposite -- the axles will be glued into the chassis, with the wheels rotating on the axles.
The Trailer Bed And Trailer Front Wall

The trailer bed is 1/2" x 3" x 10". The trailer front wall is 1/2" x 1 1/4" x 3". That 1/2" thickness figure is a bit of a complication -- I don't have a thickness planer. I'll have to resaw and hand plane some 3/4" stock; not one of my favourite activities.

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That turned out not too badly -- I only had to make two attempts on the trailer bed. Here's what I have so far.

Where I went wrong on the trailer bed the first time was in trying to use stock that had the outskirts of knots at the ends. When thickness planing it, the knot outskirts tore out, like so.

Not useable. It's ok to use knotty material, but avoid knots or knot outskirts at ends of pieces.

The hand thickness planing was a chore; I'm glad that I'm working with softwood here. Maple would be more difficult -- a lot of plane sharpening would be in order.

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The Rear Axle Mount

I have that made from a scrap of softwood. Here it is.

It's 7/8" x 1 1/8" x 3", bored through in two places 1/4" diameter for wheel axles.

There was an error in the drawing for this part that fortunately I caught in time. Had I not caught the error, I'd have ended up with the two axle bores too close together. You can't trust how-to drawings to be error free -- it's wise to go over them and make sure that dimensions add up correctly.

Wheel Bores

Since I mean to have the wheels turn freely on the 1/4" diameter axles, I have to give some attention to wheel bore diameter here.

The wheels I bought have 1/4" diameter bores. If I just install those wheels on 1/4" diameter axles, I'll have binding wheels. This is where a set of letter size drills comes in handy. Letter size drill 'F' is 0.257" diameter -- 0.007" greater than 1/4". So, boring out all the wheels with a letter size 'F' drill gives me nice, free rolling wheels. It's an important consideration; any child with his wits about him would rightfully perceive binding wheels as a defect in his toy. It would diminish his enjoyment of it.

Wheel Spacing (Axial Clearance)

Another consideration for freely rotating wheels is axial clearance; wheels mustn't bind between a vehicle's chassis and an axle's hub -- some axial slop is called for. Some plastic shim stock is helpful for establishing axial clearance at wheel installation time. I have a plastic display card from a store gift certificate that's exactly 1/32" thick. I cut it and notched it to give me a pair of wheel installation shims, like so.

Insert the shims between a wheel and the vehicle's chassis while the axle glue-up is tacking, and you'll end up with about the right amount of axial clearance for a free rolling wheel.

Progress So Far

Here's a view of what I've got done so far.

The trailer's rear axle mount and front wall are glued in place, but they lack reinforcement. I'll be adding dowels for that. I want this truck to be able to take rough handling without anything breaking loose.

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Here are the reinforcement dowels installed, awaiting flush-trimming with a chisel.

A toy like this one is liable to be in for some rough treatment, and needs to be able to take it without anything breaking.

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Taking Shape

Progress so far.

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All Done

The 'logs' are from apple tree branches.

That was a delightful and satisfying project. I must pursue more.

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[1] In fairness to the text's author, I'll make a wheel per his instructions and see how it turns out, and how it compares to the Lee Valley wheels.

There's a slight difficulty right from the get-go; i.e. 1/2" thick stock is called for. 1/2" thick stock is not something that's readily available -- it has to be resawn and/or planed from thicker stock. The text makes no mention of that.

I come across this often in published plans -- authors blithely call for stock thicknesses that one will not find at a typical lumber outlet, with nary a word about how one is to obtain such thicknesses.

Anyway, I'll resaw and hand plane a bit of 3/4" stock; I only need enough for one wheel here.

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And here's my resawn and hand planed wheel blank from a scrap of softwood that was destined for the stove.

Hand thickness planing is quite a skill, and I don't really have it. What you see in the photo is a variable thickness approximation of 1/2" that will suffice for this exercise. I'd love to have a thickness planer in my shop, but those things aren't cheap.

Next up is to bore a hub recess, 3/4" diameter x 1/8" deep, with a Forstner bit. Then, I can apply my circle cutter to get the basic wheel cut out of the blank.

- - -

And here we are with the circle cutting just done.

The text then has you bore out the circle cutter's pilot hole to 1/4" diameter, and mount the wheel on a simple 1/4" mandrel for sanding and chamfering in the drill press. Here we are with that operation just completed.

And here's my shop-made wheel next to a Lee Valley wheel.

If you don't mind the austere plainness of the shop-made item compared to the factory-made wheel, the shop-made wheel is quite acceptable for toy making. I can't fault the text's author at all for his approach to fabricating toy wheels.

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A couple of closing notes:
  • Wheel material really should be hardwood, and the text's choice of maple is a good one. 
  •  In any shop with a wood lathe, it's obvious that the wood lathe is the preferable machine for the sanding and chamfering operation. I only used the drill press to adhere to the text's instruction. I've never much cared for the use of a drill press as a 'vertical lathe'.
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