JohnH
Member
I just read this post. Awesome work on this engine!
Can't wait to get mine started.
Can't wait to get mine started.
Chevy V8 Scale Engine Plane
- Thread starter TrashCo
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Help Support Home Model Engine Machinist Forum:
Looks like there are at least three of us working on the Li'l Demon. That's really cool. Keep the info coming.
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Getting close, still a lot of small stuff to make and final assembly.
Those brass carbs are beautiful! And the linkage is really something.
I’ve been putting it in the microwave every now and then to keep it hot. The first time I did this I put the measuring cup on the stove burner. CRACK! Then I read that it is not for stovetop use. My wife was not amused. I can see the tiny stream of bubbles coming from the steel parts, so it is working.
Kitchen engineering operations can be a source of domestic friction. I set a useful precedent when I used the oven to sweat the valve guides out of the cylinder head of my wife's bike!
I feel your pain. I did the same thing to the oil pan. The alum works but you need to keep it hot.
I bought a cheap electric burner off Amazon and ceramic Corningware pan from eBay. For some reason, the spouse didn't want me using her Corningware or the stove top.
Keeping it warm didn’t do much yesterday. I removed a broken tap from the carb this way, maybe the extra mass of the block is making it difficult to keep it hot. So I put it in the oven set at just below the boiling point and I’ll leave it for several hours. I can see more bubbles streaming from the steel parts, so I think it is working better.
It took most of a day for me. You can pick out some of the loosened pieces to give the alum a better chance at getting to the remaining bits.
Novice question. I'm having no luck with the crankshaft. Bent another trial crank, this time with 12L14 instead of aluminum. I got through the four rod journals and was working on the farthest end from the spindle when it grabbed, spit out two "cookies" and bent the crank. I get lots of chatter and then the tool grabs. I have the tool as close to on center as I can get it and have it honed quite sharp. Using HSS at 180 rpm. Stock is 1" round.
The process I tried is to do all the offset turning first, the four rod journals. I mill away the excess of the furthest journal away from the spindle and turn it to size. I then mill away the second rod journal and stick a "cookie" in the first and turn. Rinse and repeat for the third and fourth. I then started to turn the crank end furthest from the spindle to size. That was where it grabbed and bent the crank.
Should I do the work sequentially from the end away from the spindle instead so that the crank is stiffer from the driven end?
The process I tried is to do all the offset turning first, the four rod journals. I mill away the excess of the furthest journal away from the spindle and turn it to size. I then mill away the second rod journal and stick a "cookie" in the first and turn. Rinse and repeat for the third and fourth. I then started to turn the crank end furthest from the spindle to size. That was where it grabbed and bent the crank.
Should I do the work sequentially from the end away from the spindle instead so that the crank is stiffer from the driven end?
Cogsy
Well-Known Member
For my V4 I milled all the excess away before I started any turning and then finish machined starting from the tailstock end and worked towards the spindle. I used 1144 stressproof which machines very nicely and is less prone to warping after machining.
I wonder about your 'cookies' and how well they fit. If they're not a tight fit your crank can flex and if they're too tight it'll bow. I made up some mini jack-screws just using a short bolt with an adjusting nut and a second nut to lock it in place.
I can't remember what tool I used for the crank ends but for the journals and mains I used a narrow parting blade which I ground a bifurcated end on, so that I basically had a narrow, combined, left and right handed cutter. It was no good for plunge cutting of course, but you just walk it side to side with a shallow depth of cut and it works well. Chatter was virtually nonexistent.
I wonder about your 'cookies' and how well they fit. If they're not a tight fit your crank can flex and if they're too tight it'll bow. I made up some mini jack-screws just using a short bolt with an adjusting nut and a second nut to lock it in place.
I can't remember what tool I used for the crank ends but for the journals and mains I used a narrow parting blade which I ground a bifurcated end on, so that I basically had a narrow, combined, left and right handed cutter. It was no good for plunge cutting of course, but you just walk it side to side with a shallow depth of cut and it works well. Chatter was virtually nonexistent.
Can any member tell me what I can use for the crankshaft instead of 1144, have tried to buy from USA but sellers say because of America export laws we decline the sale to you. I am in Australia
Hi John from down under! One of the ways I use is to rough out all the journals a bit at a time this seems to spread the turning load proportionately as you go. In your case I would suggest using a fixed steady to support the shaft to turn the end main journals and i would shorten the length of the shaft to just over finished length this will reduce the flexing at the weak points where you have finished the journals. Looking at the photo you maybe could have chucked the shaft and turned the main journal at the head stock end and put no load on the weaker areas. Hope this helps
More..
Remove as little material as possible
When you adjust the tool or adjust something, rotate the chuck by hand before you turn on the lathe
calm down and be patient , Drink a cup of coffee if needed
Remove as little material as possible
When you adjust the tool or adjust something, rotate the chuck by hand before you turn on the lathe
calm down and be patient , Drink a cup of coffee if needed
There are some tricks to making a multi-plane crankshaft that we use to build crankshafts for the Black Widow V-8s which are supercharged and regularly run up to 10,000 RPM for short periods of time. We make them from 4130 or 4140 alloy steel (chromealloy) and they are not hardened. The majority of the metal is removed by milling so the final turning is relatively easy. An article on how to do this is in Issue #30 of Model Engine Builder but here are the major 'tricks' of the trade:
The raw crankshaft is supported everywhere but at the journal or throw this is being machined. Milling is done with a conventional cutter but the lathe work is with a specially ground tool.
Crankshaft reinforcement is a clamped sleeve in two parts.
Ready to rough mill another journal
The tool bit looks like this and is just slightly narrower than the width of the bearing surfaces so it can cut from cheek-to-cheek. Other than a final finish with abrasive cloth, this is the way the journals are brought down to almost final diameter. The tool bit cuts just slightly over one-half of the journal width. The tips of the tool HAVE to be parallel to the long axis of the crankshaft or you will get a 'stepped' bearing in the middle.
The crankshafts are not hardened and some of the engines are now over 15 years old with no rebuilds required even though they have endured running at many shows.
I hope this helps.
Mike Rehmus
Editor
Model Engine Builder magazine
The raw crankshaft is supported everywhere but at the journal or throw this is being machined. Milling is done with a conventional cutter but the lathe work is with a specially ground tool.
Crankshaft reinforcement is a clamped sleeve in two parts.
Ready to rough mill another journal
The tool bit looks like this and is just slightly narrower than the width of the bearing surfaces so it can cut from cheek-to-cheek. Other than a final finish with abrasive cloth, this is the way the journals are brought down to almost final diameter. The tool bit cuts just slightly over one-half of the journal width. The tips of the tool HAVE to be parallel to the long axis of the crankshaft or you will get a 'stepped' bearing in the middle.
The crankshafts are not hardened and some of the engines are now over 15 years old with no rebuilds required even though they have endured running at many shows.
I hope this helps.
Mike Rehmus
Editor
Model Engine Builder magazine
Good suggestions all.
Cogsy, the cookies were a good light press fit. They were tapered a couple of tenths on the rod journal end. The two that fell out were due to the twisting of the rod journals. I milled away the rod journals one at a time, not all at once, to minimize the twist they would be subjected to. That went reasonably well but there was a lot of chatter. My tool is wide, .163 with no center relief which may be the culpret. I tried a 3/32" parting toolbut it was worse due to the extensioin required to clear when offset turning. The tool I am using is much stiffer and resists twisting better. I think there is some twisting going on due to the length of the stock. The finished OAL will be 7". The stock I am using 12" long with the part centered. That leaves an extra 2.5" on each end so I can get a lathe dog on with clearance for the carriage and minimizes tailstock extension. I might be able to reduce this some.
Jowen, I'm doing all the turning between centers. I have debated about using my collet chuck for the mains and ends but was concerned about maintaining concentricity. Using a collet would be much easier and would eliminate most of the twisting issues. Would someone comment on using a collet for the mains and ends versus turning between centers? Flipping the part and using a steady sound like they are doable without concetricity issues.
minh-than, ahh - stress relief. When things like this happen I just have to shut everything down, clean up, walk away, and reflect on what happened. The problem here is I don't have enough experience with long, single-piece crankshafts to figure out what I am doing wrong. This was a test run for learning purposes and failure was an option.
Cogsy, the cookies were a good light press fit. They were tapered a couple of tenths on the rod journal end. The two that fell out were due to the twisting of the rod journals. I milled away the rod journals one at a time, not all at once, to minimize the twist they would be subjected to. That went reasonably well but there was a lot of chatter. My tool is wide, .163 with no center relief which may be the culpret. I tried a 3/32" parting toolbut it was worse due to the extensioin required to clear when offset turning. The tool I am using is much stiffer and resists twisting better. I think there is some twisting going on due to the length of the stock. The finished OAL will be 7". The stock I am using 12" long with the part centered. That leaves an extra 2.5" on each end so I can get a lathe dog on with clearance for the carriage and minimizes tailstock extension. I might be able to reduce this some.
Jowen, I'm doing all the turning between centers. I have debated about using my collet chuck for the mains and ends but was concerned about maintaining concentricity. Using a collet would be much easier and would eliminate most of the twisting issues. Would someone comment on using a collet for the mains and ends versus turning between centers? Flipping the part and using a steady sound like they are doable without concetricity issues.
minh-than, ahh - stress relief. When things like this happen I just have to shut everything down, clean up, walk away, and reflect on what happened. The problem here is I don't have enough experience with long, single-piece crankshafts to figure out what I am doing wrong. This was a test run for learning purposes and failure was an option.
I previously tried a sleeve like that when I was using aluminum bar for tests. I used spiral thread hose clamps and it was not strong enough. I don't have a welder but I might be able to braze the cylinders on the end.
My tool bit is essentially that design without the center relief and wider. I will reduce the width and relieve the center. I can't believe how clean the grinde is on your tool. Was it done on a tool and cutter grinder or by hand?
