ORIGINAL: earlwb
...You know, I think you are correct. They used to include two tools in a engine box, when you bought it. You needed two tools, one to hold the cylinder as you loosenedor tightened up a new glow head or something...
That is correct. For early Cox engines, you would insert one wrench in the exhaust slot and the other on the glow plug. Since the cylinder walls were thin on the early engines, you had to make sure the wrench was inserted in the exhaust properly or you could burr the cylinder.
Some later engines had either two narrow slits or had the exhaust often covered with wire mesh or a muffler, etc. so someone came up with milling the top fin to make a slot, and creating a wrench to fit that slot.
Here are some of my Cox engines. First we have some product engines showing the different exhausts. Next are various Golden Bees. Some Thermal Hoppers. Some TD's (top row are .09's, bottom right is early .15, rest are .049's. Then Space Bug Jr's (they came in various tank colors). Finally we compare size og Black Widow to Space Bug. I hope the pics come up in the right sequence.
If you have questions about some other Cox engines, I may have pics...except Space Hopper. [
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George