I finally got the standard done for my poppin' engine (see flinging it across the shop). I could use some advice on building the crank. I have never built a crank this small or built up from pieces. My first attempt was less than perfect. I think the parts separated some during the jig drilling (one stacked on top the other). Any tips on how to tackle this part would be appreciated.
poppin crank shaft ?
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rake60
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The Poppin crank was a challenge for me as well.
The plans show fabricating the crank with the main shaft the whole length then cutting
away the center section. I'm a better machinist than that, I could make it from 5 pieces
rather then 4 and eliminate the need to cut that center section away.
WRONG!
I went back to the plans design and made as shown.
The fit was stuff to stuff, meaning it could be put together with a little help from a
light plastic hammer.
Then the joints to the throw beams were soft soldered tight, and the center section
was cut out.
That time it worked!
BTW I have something that resembles the standard for a Poppin in my "Recycle Box"
Rick
The plans show fabricating the crank with the main shaft the whole length then cutting
away the center section. I'm a better machinist than that, I could make it from 5 pieces
rather then 4 and eliminate the need to cut that center section away.
WRONG!
I went back to the plans design and made as shown.
The fit was stuff to stuff, meaning it could be put together with a little help from a
light plastic hammer.
Then the joints to the throw beams were soft soldered tight, and the center section
was cut out.
That time it worked!
BTW I have something that resembles the standard for a Poppin in my "Recycle Box"
Rick
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I brought the crank throws to finished size and then drilled and reamed them individually in the mill. Actually I used a 5/32 end mill that I knew cut a little under size to poke holes through them and then ran a reamer through to finish to size. By taking the backlash out by approaching the hole location from the same direction for both holes, they will be more than accurate enough as far as distance between them. You don't really have to be concerned if the hole pattern if off a little bit from the ends, only that the two holes are the same distance apart on both parts.
In years past I used the match drilling technique by soft soldering two slightly oversize blanks together, then machining them to width and drilling and reaming the holes. Heat and separate the parts and then file off the thin solder layer on each part. The solder removes easily as it is soft and cuts easily.
When assembling, I made a rectangular spacer to fit between the two throws and slid it between the crankshaft and the crankpin tomake sure the two throws were parallel to each other. The crankshaft was made as one piece and everything was assembled using Loctite 680. Then the center section of the crankshaft was removed by sawing, milling and filing.
My finished Poppin is at:
http://www.homemodelenginemachinist.com/index.php?topic=1916.0
Gail in NM,USA
In years past I used the match drilling technique by soft soldering two slightly oversize blanks together, then machining them to width and drilling and reaming the holes. Heat and separate the parts and then file off the thin solder layer on each part. The solder removes easily as it is soft and cuts easily.
When assembling, I made a rectangular spacer to fit between the two throws and slid it between the crankshaft and the crankpin tomake sure the two throws were parallel to each other. The crankshaft was made as one piece and everything was assembled using Loctite 680. Then the center section of the crankshaft was removed by sawing, milling and filing.
My finished Poppin is at:
http://www.homemodelenginemachinist.com/index.php?topic=1916.0
Gail in NM,USA
Thanks for the advice. I tried to drill the throws both at the same time. I think that was my mistake. I am pretty sure they pulled apart slightly causing the hole to go off square. Because, when i assembled the silly thing one end of the throws was .209 apart and the other was .190. I think next time I will drill them one at a time, clamped to the table.
This project has been a make 2, to get one. I guess I am used to Phil Duclos engines and the nice LARGE parts.
This project has been a make 2, to get one. I guess I am used to Phil Duclos engines and the nice LARGE parts.
Divided He ad
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Hi BM, glad you stuck with it
Just a little bit for you to read, a good post on both making multiples and a useful way to make crankshafts.
http://www.homemodelenginemachinist.com/index.php?topic=862.0
Hope this helps?
Ralph.
Just a little bit for you to read, a good post on both making multiples and a useful way to make crankshafts.
http://www.homemodelenginemachinist.com/index.php?topic=862.0
Hope this helps?
Ralph.
rake60
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BMyers said:
And I should have seen that! LOL
TIG rods are usually dead on size.
Anything would actually work. Drilling the joint is going to create an internal burr.
Just try drilling through a joint then dismantling it.
Anything you put into that hole as a pin is just reinforcement.
Rick
Gentlemen,
thank you for the replies. Crank #2 was a success. I spent last night making a vise stop, so I could mill each throw individually. I used advise from another post of Bogstandard's. I cant wait for the bearings to arrive so I can test spin the crank in the standard.
thank you for the replies. Crank #2 was a success. I spent last night making a vise stop, so I could mill each throw individually. I used advise from another post of Bogstandard's. I cant wait for the bearings to arrive so I can test spin the crank in the standard.
Divided He ad
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Hey BM, it's easy when you know how..... That's why I as you do find everything so hard the first ..... erm many times!!
As Rick said, 'don't give up!'
At least you sound like you have found that fighting spirit ;D
Keep us posted on the progress,
Ralph.
As Rick said, 'don't give up!'
At least you sound like you have found that fighting spirit ;D
Keep us posted on the progress,
Ralph.
rake60
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As I said, I liked your idea of pinning the joints.
My Poppin has been run to death and it's time to make a new one.
I was playing with the old crank today and ended up with this:
Those pins are small wire nails I found in the shop.
I drilled the joints for a stuff to stuff fit, tapped the wire nails in and nipped the opposite
ends off leaving about 1/16" sticking out. A few raps with a small ball peen hammer and I
have rivits, or something close to that. :big:
When I do my new build on the Poppin that's what I plan to do.
Rick
My Poppin has been run to death and it's time to make a new one.
I was playing with the old crank today and ended up with this:
Those pins are small wire nails I found in the shop.
I drilled the joints for a stuff to stuff fit, tapped the wire nails in and nipped the opposite
ends off leaving about 1/16" sticking out. A few raps with a small ball peen hammer and I
have rivits, or something close to that. :big:
When I do my new build on the Poppin that's what I plan to do.
Rick
nice Rake, I used 1/16" fill rod. drilled the holes. pinned it with pins a little long, mushroomed the pins and filed smooth. The pinning worked good. I need to get a 5/32 ream, drilling isnt working for me. Maybe after 4 or 5 I'll get a system worked out
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