Making rod bearing inserts, Attention Machinist

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Buccaneer
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Making rod bearing inserts, Attention Machinist

Postby Buccaneer » Tue Jun 12, 2018 1:01 pm

The Speedster I'm working on had homemade brass / bronze rod bearing
inserts. Whoever made them did a nice job, but they weren't fitted
correctly, as one couldn't tighten the rod cap bolts tight without
the inserts binding on the crankshaft. This problem was overcome by
the rod bolts being loose, but wired in place.

I re-fit the first one by sanding down the ends of the insert halves so
the cap would mate tightly with the connecting rod, then reamed out
the bushings to a nice fit to the crankshaft.
The first one turned out nice. I screwed up the second one and got
the "hole" too big.
(I never claimed to be a machinist, but played on in the garage on occasion.)

I ordered some 660 bronze rod to make a new set of inserts.
I'm trying to think ahead how best to make the new inserts.
Turning the OD to fit in the rod, and ID to fit the crank is no problem,
but when a person goes to cut the bushing in half to make it
into "inserts", the inserts become shorter by however wide the saw kerf is.
If the insert ends don't "butt" tight together, they will be loose in the
rod and turn.
Also, I have nothing to cut the bushing in half to make inserts, other than
a hacksaw, which I'm never made a straight cut with in my life.
I know babbit bearings have shims between the rod cap and rod, that
can be removed as needed to re-fit the rod to the crank, but my rod
cap and rod body have notched, overlapping ends.
Ideas greatly appreciated.
Thanks.
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dmbono
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Re: Making rod bearing inserts, Attention Machinist

Postby dmbono » Tue Jun 12, 2018 3:48 pm

Cut the rod to length of bush plus 1" or so for chucking. Split the bronze rod with hacksaw, then file or belt sand surfaces flat. Then soft solder together. Then mount in a four jaw chuck, turn OD and bore Id right to size, then part off. Heat to separate the halves.

That cut joint doesn't have to be perfect.
Dave

FrankR
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Location: Florida

Re: Making rod bearing inserts, Attention Machinist

Postby FrankR » Tue Jun 12, 2018 5:32 pm

Does it really matter if the inserts rotate in the rod?

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Buccaneer
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Re: Making rod bearing inserts, Attention Machinist

Postby Buccaneer » Tue Jun 12, 2018 6:54 pm

dmbono wrote:Cut the rod to length of bush plus 1" or so for chucking. Split the bronze rod with hacksaw, then file or belt sand surfaces flat. Then soft solder together. Then mount in a four jaw chuck, turn OD and bore Id right to size, then part off. Heat to separate the halves.

That cut joint doesn't have to be perfect.
Dave


Interesting way to go about this problem. Sounds "do-able", but I only have a 3 jaw chuck
for my old Logan lathe, but perhaps it would work?
By "soft solder", do you mean anything but "silver solder" ?
Thanks!

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Buccaneer
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Re: Making rod bearing inserts, Attention Machinist

Postby Buccaneer » Tue Jun 12, 2018 6:58 pm

FrankR wrote:Does it really matter if the inserts rotate in the rod?


Frank, that was a "bad thing" to have bearing inserts rotate when
I went to Vo-Tech in 1975. I presume you loose some heat transfer
between the inserts and rod if the inserts are loose. Also, if
the inserts rotated too much, I suppose they could wear.
That being said, "I have no idea if it would matter in my situation!"

FrankR
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Joined: Tue Mar 10, 2015 6:32 pm
Location: Florida

Re: Making rod bearing inserts, Attention Machinist

Postby FrankR » Tue Jun 12, 2018 8:16 pm

Well yeah, but didn't those auto inserts spin because they seized to the crank? I'm not a car mechanic though.

amuller
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Re: Making rod bearing inserts, Attention Machinist

Postby amuller » Tue Jun 12, 2018 10:24 pm

Interesting discussion. I'd say you want a little "crush" on the OD of the inserts to keep them in place and encourage them to stay round. is your lathe big enough that you could bore the rods with the inserts in place and the caps torqued down? Or do you have access to a Sunnen rod hone or an expansion reamer?

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Buccaneer
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Re: Making rod bearing inserts, Attention Machinist

Postby Buccaneer » Wed Jun 13, 2018 8:19 am

amuller wrote:Interesting discussion. I'd say you want a little "crush" on the OD of the inserts to keep them in place and encourage them to stay round. is your lathe big enough that you could bore the rods with the inserts in place and the caps torqued down? Or do you have access to a Sunnen rod hone or an expansion reamer?


I have no way to mount the rod in the lathe, especially with a 3 jaw chuck.
Not sure if my 11" swing would be big enough.
I was reaming the inserts out to size them with the rod cap on, by
mounting them in a vise and using an adjustable reamer. Perhaps
a little crude, but worked. I haven't seen a Sunnen honing machine in these parts
for 20 years.

I was thinking that maybe I could turn the OD of the bushing, and
approximate ID, cut the bushing in half to make the inserts, apply solder to the insert ends and
sand them down until I got the required "crush" , then finish boring the ID.
What about that plan? Similar to suggested, but maybe "easier".

dmbono
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Re: Making rod bearing inserts, Attention Machinist

Postby dmbono » Wed Jun 13, 2018 8:55 am

You can still use my method with a three jaw. The soldered blank is no longer round, but you only need to get the split line roughly centered. I've made many split bushings by this method. No, you don't want the bushing to rotate in the rod. Yes, soft solder is used, not silver solder. That means any type of plumbing solder will do.

dmbono
Posts: 87
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Re: Making rod bearing inserts, Attention Machinist

Postby dmbono » Wed Jun 13, 2018 8:57 am

This motor was designed with roller bearings, so any bushing is going to be a compromise.


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