Working on a decorative wagon wheel in wood, but I'd really like to put
a metal tire on it. Now, that's no trick if it's just for looks--make a
steel ring that's close enough to the dimension that a little epoxy
under it will hold it, but the devil in me wants to do a proper job and
shrink the thing.
Trouble is that this is a no-burn area so I can't just light a fire in
the back yard and heat the tire.
So, any ideas on how to go about this? The wheel is 2 feet in diameter,
making the tire too big to fit in a barbecue or the like. If I was
making a bunch of 'em I'd be tempted to just build a charcoal pit big
enough and call it a barbie, but that's a lot of work for one wheel.
And yeah, I know I can find a blacksmith, but I'm more interested in the
making than in having a wheel.
That's another good idea, appeals to the small boy in me, and is cheaper
than an oxyacetylene rig. So should I go for the 500,000 BTU Red
Dragon, the 100,000, whatever Home Despot has, or the 12.99 Harbor
Wish I'd thought about using one of those when I was trying to get my
muffler off a while back, but I'd have probably just set the Jeep on fire.
Also, the heat content of acetylene is far less than that of propane, so propane
is better for bulk heating. I learned this from a book on brazing and silver
soldering. The author is a UK model builder, and he makes silver-soldered brass
boilers for model steam engines.
I have a Home Despot weedburner, and while it does work, it is awkward to use
because it lacks a built-in lighter, so you cannot turn it on and off so easily.
An ordinary spark lighter didn't work, and I ended up using a small propane
torch as a lighter. Clumsy. So, I would recommend getting a unit with built in
lighter. I'll probably buy one someday.
I have no experience with the HF unit.
I would think that 100,000 BTU/hr is enough, but you will need the firebricks to
make a simple muffle to contain and focus the heat.
If you can manage the charcoal ring fire, that may be easier. Use the
weedburner to light the charcoal. Firebricks are still useful. Or half-bricks.
For doing hot work on my wooden workbench, I went down to a local brickyard and
bought $35 worth of ordinary firebricks and half-bricks. (Have the shape and
density of an ordinary red brick, but are yellow; used to line fireplaces.)
When I need to do some hot work, I make a cleverly arranged pile of bricks on
the bench and get to work. With a muffle, I can easily get small objects up to
a bright orange heat. After it all cools, the bricks go back to their storage
pile. The only scorch marks on the bench are where I didn't pile enough bricks
in place, and some flame spilled over the edge and impinged on the wood. The
backside of a full brick does not get hot enough to be a problem.
Unh. Too much of a good thing.
For a muffler, I would guess that an air-acetylene turbotorch would work. Or
air-propane turbotorch. But I've never had to use a torch on a muffler. It was
cheaper in time to simply cut the entire old exhaust system off right up to the
cast iron manifold using a cold chisel, and replace all that rusty tin. At
least on the Volvos of the day, with care you could perhaps save the long pipe
(which ran the hottest and so corroded the least), but it was not worth the
Well, it ain't much, really. If you heated it up 500F, you'd get a 1/4"
(roughly) circumferential expansion, which would be 1/4 over pi inches in
diameter, or roughly a bit more than 1/16" diametral expansion.
That's enough, I'd say, to get it over a well-sized wheel. If not - if
you wanted to pull the wheel together tighter than you built it - heat it
up 1000F for an 1/8" increase.
On a wooden wheel, what you really need to do is make sure it will shrink
down further than the amount it burns away the wood before it's below
450F. That's more dependent upon the skill of the wheelwright in
mounting and chilling the tire than it is upon the actual temperature to
which it's heated.
Calculating the change in circumference is the 'hard way' to get the answer.
A 'hole' in a piece of 'something'(anything) expands at the *exactly* the
same rate as the material surrounding it.
So, the diameter will increase by 24*.00000645 inches per degree or,
Assuming 70f ambient. heating to 500F gets 0.0665+" on the diameter, which
is almost exactly 1/15th of an inch. heating to 1000F gets 0.1439+" just over
The tricky part is manhandling the two parts so the surfaces stay "parallel"
from inner side to outer side, and getting things in place before the tire
I'd be tempted to 'cheat', and subject the wooden wheel to a dry ice (or
similar) treatment, to -shrink- it as much as possible.
Also get the wood as _dry_ as possible before mounting the tire, and then
let it absorb moisture back to 'normal' level. every little bit helps. ;)
A *lot* of places have no *open* fire regulations, at least part of the time.
There are "Red Flag" warnings issued here on dry days (quite often in the
Winter). Some areas require a "burn permit" for an open fire.
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