Another Radial - this time 18 Cylinders

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Jun 18, 2020
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Wow that was a lot o reading. I s a huge amount of research and trial error and redo happening in the quest of perfection. I can’t in any way take away from this. Great work , all of the contributors.
Add a couple of comments myself. Certainly not in any attempt o refute what as been said and done I’ll just add my experience as automotive engine builder ant ex top fuel racer.
Kinda backing up let’s look at leak testing. This has been a backbone of the auto world since he ‘60 maybe even before that. About that time Sunnen honining was popular. I even ran the shop hone machine as a machinist apprentice . This simple device allowed unbelievable tolerances to be achieved in a relatively crue machine shop virtually every type of metal and semi metal was honed to perfection as needed the Sunnen rep was in the shop about every week with the latest things. I think we has samples of about their full line. This is where I’ll get to the leak tester shortly . A lot of cylinders were done carbide rings for the beverage can industry were a big part of the company I worked for. They got into war materials as the viet bam was grew there were lots of close tolerance items honed. Temp control both in inspection and as the shop machines was carefully monitored all the one there were gages and surface finish devices that were brand new to the industry that ere brought in almost daily the US government paid dearly fir these and the training to use them . I was fortunate to be a part of his. Just breathing on parts could cause measurable changes in size . You didn’t just walk into the inspection dept. there was an air lock. If you ere hot and sweaty, you had to cool off before the door opened . You often had to request permission to be admitted if you had a good reason you ere allowed in . If you just wanted a tool verified you often handed it through s portal after calibration it would be returned. Anyway it gave us apprentices a good introduction to what tolerances were about.

leak tester. As soon as got into big time drag racing I found leak testers Sunnen was the big maker of these and it was one of your first race tools they were very expensive then but easy to use. I just looked on Amazon and you can get a nice set for under $100 now. I think they were around $400 back then in 1960 dollars . Weeks pay. These all work about the same you simply have a spark plug to air hose adaptor on the line from the tester it I turn is hooked to shop air or air supply. You set the piston to top dead center You adjust to fluid flow to the shop air the hook the spark plug line up and read the leakage. Some times you can pull the engine into compression and read at a certain angle or position of the piston . Some of these read in reverse but the number comes out the same . We used top dead center as that was where cylinder damage occurred mostly it would indicate a lifted ring land about 2% was considered good 5% and you had burned piston . I haven’t used this on model engines . At the time I was into high performance glow plug engines
These had ABC cylinders aluminum cylinder bronze liner with chrome facing the pistons ere lapped to slightly stick when cold at top center. This went away as soon as they ere run. Most of these engines were from . 40 cu in to . 91 chin rpm was abou 20 k plus or minus. Life was a few minutes. Very high nitro fuels later came weed eater types . Ironically I don’t recall leak testing one rpm with a given prop was the gage.

moving on in life I was laid off of my engineering job an went to Huntsville to work at international diesel . Here was a brand new engine manufacturing plant my honing experience put in charge of the honing operation of a v8 Diesel engine this was a fully automated manufacturing operation with just in time delivery of raw castings to finished ready to install engines. Here the blocks came to the hone with about .005 stock to be honed out for finishing this was done in three steps rough hone took about .002 1/5 out while the second step brought in the size to about .0005 with the final plateaue brought to final size al honed were cubic boron if any honed were changed during a shif it was rare it required a special inspection of a given block. It was easy to just poke a button and the block was electronically marked and diverted to the inspection station. Where a full coordinate measurement was done and recorded. There was an in process inspection I had to do on ever 50 th block this involved temp verification gage qualification then plugging in the gages or direct input to the data base .
a little bit about these gages. These were all air calibrated obviously pressure monitored ring gages slipped over plug gages and the leakage vs pressure exactly monitored and input to the data base. Tolerances were in the 6th decimal place adjusted automatically to temps.
It was unusual to reject a single block in a 10-12 hour shift . These blocks were processed one block per minute through each station so a lot of cast iron got move d each night . Ironically this job paid better than double my engineering job plus I got room and board. Essentially all the food I could eat I had lots of sirloin and hot beef lunches I didn’t gain an ounce 12 hours a day 7 days a week for almost two years bough me a new van new car and new diesel dusky truck . Plus one heck of an experience in automation. My main engineering line . I even got to work in the tool setup and grinding room for an extended period. Again automated machinery incredible tools I had never seen before or since. Automated carbide drill making machine also made carbide end mills fro round stock all this stuff went into the central computer . I had run a much smaller central computer including cad support before so I knew a little about it . Pretty primitive by today’s standard.
I really got off track here sorry

the point I was after that I YHINK some are missing is that when machining a cylinder bore for example there is a layer or skin of torn metal that the boring tool or drill as the case may be that needs to be removed by honing or as some are doing by lapping . Lapping being the hard time consuming way. In the auto shop when boring a cylinder about .005 was left fir finishing again honing was the answere about.0025 was taken out rough honing the finishing brought the cyl to size leaving the final cross hatch finish. What this did was remove the torn metal leaving a near perfect round well surfaced surface for the rings to seat on rings ere supposed to be ready to run so I won’t get into finishing racers use a chrome faced top ring either dyke ring or plain ring second rings are filled moly rings today. They used to be cast iron with taper some times reverse taper inner chamfer some times overlap or hapless some very fancy have insert rings oiled rings have been multi piece with expander as long as I’ve been around. There has always been the dot have gaps alighted. The diesel plant had a piston ring installation station that installed ring exactly oriented interesting machine . One Christmas vacation my room mate and I were asked to disassemble some 200 engines double time and a half. Hard to pass up so we did we had to record ring position . Not a single piston of all those engines had the rings in the original position there was no way this was a failure ofvthe assembly process there were just too many checks and balances for this to happen. We put wash rod and piston in special boxes for inspection the company engineering mgr came down to see us ripping these engines apart he looked at the piston rings and just shook his head. I can’t feel you how many race engines I’ve seen the same ring rarely are the rings alighted as installed unless the engine blows up before it gets very far down the track . I’ve raken lots of high mileage engines apart with rings in every location. We even did a leak test on a new engine with rings alighted as usual and others alighted @wrong” no difference . A model maybe I don’t know models don’t scale very well so some full size things just don’t apply . I love to see test results . Fir now I just stagger as we have always done . I’m open to new testing anytime



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Dec 12, 2008
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Hi Terry. I am making the Hodgson 9 cyl Radial and I know you used the Jerry Howel design for the distributor for your H 18 Radial.
When you made the 9 cyl distributor did you use Lees design or Jerrys? I know you placed the Magnets and the Hall Effect at .900 radius on the H18 dizzys, did you do the same on the H9?

I guess what I'm asking is will the .900 radius work on the H9 like it does on the H18? I also used the Jerry Howell design dizzy.

Thanks in advance for your attention to this matter.

Ron Osborn aka ozzie46

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