The Stationary Engine Mailing List threw up some good discussions this past month to pass on GEM readers. As usual with a group of engine enthusiasts numbering around 300 on three continents, the discussion was lively to say the least, and flew off at several different tangents, including the ever faithful 'styles of restoration' argument, which I may one day bring to these pages. But I will cover myself right now by saying it is purely a matter of personal preference!! So, on to this month's subject:
Can anyone tell me if JB Weld is strong enough to make a bearing, instead of babbitt? I need new crank rod bearings on both my Renfrew Whatever and 2 HP Fuller Johnson. I am not a machinist. There is no one in my area to help me with babbitting, something I know absolutely nothing about. I do not have the equipment for grinding, finishing, polishing, etc. I want to get this engine running with the resources I do have, or with what is available.
I have read with much interest about using epoxies in place of babbitt for bearing material. While a marginally serviceable bearing could possibly be made of one of the numerable epoxies on the market, all of them would be inferior to babbitt. Babbitt's chief merit is in the fact that any dirt that will invariably find its way into your bearing will be forced into the soft bearing material and minimize the amount of scoring this dirt will do to your journal. A brass bearing or aluminum bearing is too hard to allow the dirt or grit to work its way into the bearing material where it will do little harm. JB Weld, Belzona and Devcon products are also too hard.
Pouring babbitt is really not difficult if you have any mechanical aptitude. I often pour my bearings around an undersize mandrel and bore them to size in the mill. Careful bluing and scraping would yield the same results, albeit much more slowly.
Making an insert is an option, although I fail to see any real advantage to it. The bearing boxes on many engines were rough cored, meant to be babbitted to situ. To machine the casting for an insert would be as much work as machining bearings cast in place. A bearing machined from a billet of babbitt would actually have less compressive strength than one cast and bored in situ. This is taken care of in modern engines by 'crush' as mentioned in another posting on the subject.
I am 31 years old and have been collecting engines since I was 12. I poured my first rod bearing when I was 14. If a kid can figure it out, any of you should be able to do it better. Someone expressed a concern about the paint being damaged; just accept the fact that the paint is going to need to be touched up but at least the engine will be repaired right. A rebabbitted bearing box should outlast all of us if done right and kept lubricated.
Some years ago, in a museum, I saw a beautiful Craftsman smoothing plane, displayed along with many other tools. The unusual thing was . . . it was polished brass! It was made not by a Craftsman supplier, not by a metal worker, but by a woodworker in some third world Central or South American country, simply because he needed such a plane. He was able to borrow one from a friend to copy. They had just fought a revolution, so enough empty cartridges were picked up in the jungle for the brass.
He made molds in the sandy dirt, melted the brass in a fanned wood fire, and poured his own plane! He did it with techniques that have been around for centuries. What do you suppose he would have done if he needed a simple bearing?
When I saw that, and realized what he had done, with so little, I decided that with my fairly decent shop... there was very little I couldn't do . . . if I were willing to try. That unknown woodworker has given me inspiration to accomplish many things that looked too difficult at first, and the satisfaction that such accomplishment brings. This includes making many of my own engines from castings I poured myself in my own backyard. I think the 'trying' is one of the best parts of the old iron hobby.
Let me put my two cents worth in. Yes, babbitt is one fine bearing material. Yes, dirt gets embedded in it and gets buried where it can't scratch the bearing journal. It is actually fun to do as well. We talked bearings in school one night and we were working on a Goulds pump. The old crosshead bearings were gone so we decided to rip the old babbitt out and make aluminum sleeve bearings. Well, guess what? The bore of the crosshead where we were going to press these bearings into was anything but round! We discussed what options we had. We could either machine the bores for bearings or try and pour new bearings. We made brand new guide rods for the crossheads, we then carboned them up with an acetylene torch so the bearing material wouldn't stick to them. We put the crosshead on the pins and aligned everything so it was square. We did use flux on the bearing bores. Heated some old scrap bearings in a stainless steel soup ladle and used clay to dam up the bearing bores so the babbitt wouldn't run out, and away we poured. The end result was two beautiful bearings and a lesson in how it was done. The class had a wonderful time rebuilding a piece of history and learned something that is not currently taught in machine shop. The thing is now when I find a loose engine with real sloppy bearings it's no problem because it is easy to fix.
You can have fun with Epoxy, I think it would be worth a try to see just how well it does hold up. I think the babbitt is more fun and worth the effort.
There is another way to do a temporary main or rod bearing that has been done here in Australia a few times; that is to use shoe leather of the correct thickness, smooth side to shaft. Sounds different but works and does not harm the shaft.
For anyone considering pouring babbitt bearing, I would highly recommend going to this web site: http://www.metalwebnews.com/howto/babbitt/babbitt.html and download the book. It's free. It is 90+ pages of how to pour babbitt bearings. More information than you need to know, but very well written. Even if you already know all about babbitt pouring or never intend to pour your own, I think you would find this book interesting.
If you want to epoxy it, Belzona is the best there is. If this stuff doesn't hold, nothing will. It is like JB, only the industrial version.
When you talk about a big engine, reboring and sleeving can be awfully expensive. I can see how a guy would want to save a few bucks. The bearing is another matter. There you stand to lose more than gain. If the pin is not too rough, babbitt will work, and it takes a big bearing to use 20 bucks worth of material. But if your epoxy cuts the shaft or welds itself to the shaft, the amount of damage can be extensive. Plus, the time involved will be about even. I would just hate to see someone have troubles because they were unsure of how to line the bearing with babbitt and were afraid to try.
I poured new bearings for the Buzacott 2V, both mains and the big end. I don't have a lathe so pouring is an easier option. It's a closed crank vertical for those unfamiliar. Used as slightly under size piece of bar clamped and shimmed to be fairly true in one of the existing mains. Sat crankcase on side with main caps fixed down with alum spacers for later shims and poured into the end of the upside bearing. Heated the area a bit-had no evidence at all with 'explosions.' I had candle-blacked the inside of the caps etc, so that what I got was removable shells with pegs. Let it cool, then did the other side, clamping the bar in the just cooled new bearing.
After that, undid all the prep stuff and hand scraped the mains with a scraper and bearing blue. Had to scrape the sides of the bearings first so that the crank would sit down into the bearing. As I scraped I could see it dropping into place as I sat the crank on the bearings between scrape sessions.
Did the big end by clamping it down to a steel plate parallel and again pouring the metal around a small undersize 'dowel' fixed in the middle of the assembled big-end and cap (with shims). The tinning was already on the surfaces after melting the old stuff out.
Finishing up was to clean up the dags and surface the ends of all bearings (thrust faces). So there it is!
Assembling the engine showed the crank a bit 'tight' in one position, so I left the bearings a bit slack and ran the engine for a few weeks, then tightened up a bit.
Would I do it again? You betcha! It ain't rocket science and doesn't need to be. The biggest problem was topping the pinhole leaks. That babbitt is very runny when hot. First main took five goes, second main took one go! I used muffler putty and gadgets of various kinds to keep the hot babbitt, but I think next time I'll use Play-dough or dry plaster. 90% preparation is right. Now who was it who said that?
So there you have it-lots of information about bearings, the most suitable materials to use and how to use it. Happy restoring!