Tire hammer warning

[twcoffey]

Applying heat to a tire rim with a tire mounted can be deadly.
Tire should be totally removed from rim when welding on rim.
Watch this amazing Bridgestone Tire safety video.

Ted

[HWooldridge]

Welding on any sealed container is a no-no but I should think pulling the valve on the stem would be sufficient to prevent pressure and heat buildup in the assembly.

[twcoffey]

Welding on any sealed container is a no-no but I should think pulling the valve on the stem would be sufficient to prevent pressure and heat buildup in the assembly.

The video claims otherwise.
Ted

[Jeff Seelye]

Thanks Ted, The really scary part was that there was no warning.

[Glenn]

The video has the word Pyrolosis posted in one of the slides (3:12). The dictionaries I used does not have that spelling listed, but did list pyrolysis as a chemical change brought about by the action of heat.

It is amazing that this can occur up to 24 hours later.

[HWooldridge]

Better safe than sorry... :(

[MLMartin]

thanks for sharing, i would have never though about welding on a wheel n tire, who knew the temp would rise soooo fast

[ptree]

I built a Rusty style and added a tire clutch later. I used a Gran Voyager compact spare mounted on a rear axle hub bearing assembly from same. I avoided the welding on the rim issue by using the center form another wheel and welding the pivot to that. I then used a portion of that center and just used the lug bolts to hold it all together. Has been working since about 2004.

[twcoffey]

Since I started the thread, I thought I would pipe in with my understanding of the process. I came across this video yesterday and have since been doing some study.

If you had a non-organic pressurized vessel such as steel this would not happen. Pressure would increase slightly.

The tire is an organic compound containing many elements and trapped gases in the rubber. There is a critical temperature(not very high probably around 300 to
400F) at which the gases trapped within the rubber (such as methane)are released and may ignite. What follows is a runaway self fueling ignition creating very
high temperatures. The gases of combustion causes very high pressure in a contained vessel(the tire).

In the video you will notice that comment is made that removing the valve stem and even breaking the bead will not prevent an explosion and that the rapid gas
production will re-seat the tire and the valve stem is too small to allow the large volume of gas to safely escape.

I imagine that a chunk of rubber placed in a closed steel container would explode if the container was moderately heated to around 300+ F.

When I built my tire I completely demounted the tire from the rim for welding. At the time I was unaware of this danger but just based on intuition I thought
it was better not to have the rubber near the heat.

Clay Spencer's plans shows a procedure of a loose tire on the rim using spacers and wet rags between the rim and rubber. This has been done hundreds of times
apparently without incident. Remember to keep the rags wet I thought that builders and owners should see this video so they would not weld or burn on the tire rim without knowing a possible danger. If a weld or something breaks on the rim it is temping to grab the welder and fix it.(Take your time and do it safely).

Ted

[Pat Roy]

I passed the video link on to Tom and Ray (Click & Clack the Tappet Brothers) at the radio show "Car Talk". They are not blacksmith related but they have a large audience.

[firefarm39]

Really interesting video. Who knew? Glen, you are absolutely correct on the spelling of "pyrolysis". It comes from two Greek words "pyros", meaning fire(obviously), and "lysos" or "lysis", which means dissolution or breaking apart. Think Lysol, which kills bacteria by dissolving cell walls. So the heat is breaking apart the rubber, creating flammable volatiles, which combust and create more heat, which creates more pyrolysis..........BOOM!

[twcoffey]

Really interesting video. Who knew? Glen, you are absolutely correct on the spelling of "pyrolysis". It comes from two Greek words "pyros", meaning fire(obviously), and "lysos" or "lysis", which means dissolution or breaking apart. Think Lysol, which kills bacteria by dissolving cell walls. So the heat is breaking apart the rubber, creating flammable volatiles, which combust and create more heat, which creates more pyrolysis..........BOOM!

I find it interesting that there is no evidence of the rubber actually burning(no black smoke) so it must be a gas burn which is so rapid that the rubber does not reach its ignition point before the whole thing blows.
Ted