Billet rod help
- Thread starter doodlebug-8hp
- Start date
- Tags billet
Bearings require different material than what a con rod does. For example if you made a con rod from bearing material it would break, so if you eliminate the bearing you run on the harder material that the rod is made from and it not suited for moving parts like a crank.
What are you trying to gain from not running bearing?
Running a bearing has so many advantages over the oem style, that's why they do it, from top fuel to formula 1. If there something you know that they don't? Please enlighten us, we are all here to learn, except the know it alls that are about....
Cheers Coxy.
What are you trying to gain from not running bearing?
Running a bearing has so many advantages over the oem style, that's why they do it, from top fuel to formula 1. If there something you know that they don't? Please enlighten us, we are all here to learn, except the know it alls that are about....
Cheers Coxy.
I have zero clues as to why.
As evidenced by the LAST thread, I haven't seen any effort to understand how exactly critical bearings are, and how they act as a bearing surface for an oscillating/reciprocating/rotating mass (travelling some 800+RPM's at a minimum).
This is like asking if I can run an engine without oil because REASONS.
As evidenced by the LAST thread, I haven't seen any effort to understand how exactly critical bearings are, and how they act as a bearing surface for an oscillating/reciprocating/rotating mass (travelling some 800+RPM's at a minimum).
This is like asking if I can run an engine without oil because REASONS.
Bearings are not required as evidenced by the millions of Briggs, Tecs, etc. without rod bearings.
Clearances and adequate oil are required for the two surfaces to not meet. As rpms increase, it becomes harder to maintain the oil film between the rod and bearing. This is the point where the aluminum rod meets the steel crank and starts to gall.
This is where the bearing comes in. A bearing shell has a steel or other strong material to contain the babbitt inside. The babbitt is harder to gall on the crank than the aluminum rod when there is adequate oil. In most ARC rods, the dipper has a hole that feeds oil to the bearing surface. The pressure of the oil coming up the dipper is higher with higher rpm ensuring there is adequate oil on the bearing surface.
From Wiki:
Babbitt metal is most commonly used as a thin surface layer in a complex, multi-metal structure, but its original use was as a cast-in-place bulk bearing material. Babbitt metal is characterized by its resistance to galling. Babbitt metal is soft and easily damaged, which suggests that it might be unsuitable for a bearing surface. However, its structure is made up of small hard crystals dispersed in a softer metal, which makes it a metal matrix composite. As the bearing wears, the softer metal erodes somewhat, which creates paths for lubricant between the hard high spots that provide the actual bearing surface. When tin is used as the softer metal, friction causes the tin to melt and function as a lubricant, which protects the bearing from wear when other lubricants are absent.
Clearances and adequate oil are required for the two surfaces to not meet. As rpms increase, it becomes harder to maintain the oil film between the rod and bearing. This is the point where the aluminum rod meets the steel crank and starts to gall.
This is where the bearing comes in. A bearing shell has a steel or other strong material to contain the babbitt inside. The babbitt is harder to gall on the crank than the aluminum rod when there is adequate oil. In most ARC rods, the dipper has a hole that feeds oil to the bearing surface. The pressure of the oil coming up the dipper is higher with higher rpm ensuring there is adequate oil on the bearing surface.
From Wiki:
Babbitt metal is most commonly used as a thin surface layer in a complex, multi-metal structure, but its original use was as a cast-in-place bulk bearing material. Babbitt metal is characterized by its resistance to galling. Babbitt metal is soft and easily damaged, which suggests that it might be unsuitable for a bearing surface. However, its structure is made up of small hard crystals dispersed in a softer metal, which makes it a metal matrix composite. As the bearing wears, the softer metal erodes somewhat, which creates paths for lubricant between the hard high spots that provide the actual bearing surface. When tin is used as the softer metal, friction causes the tin to melt and function as a lubricant, which protects the bearing from wear when other lubricants are absent.
Stang, thanks for the explanation of the babbit material. I noted on the Tec HS's that bring the rod caps to proper torque left just enough room for an oil film. That's why I now mark the caps before I remove them.
Is that bearingless system the reason why there is a "bump" at top and bottom of stroke? Everytime I assemble one, that kind of freaks me out. Like something is binding, only with spark and gas, it doesn't. :shrug:
Is that bearingless system the reason why there is a "bump" at top and bottom of stroke? Everytime I assemble one, that kind of freaks me out. Like something is binding, only with spark and gas, it doesn't. :shrug:
I still don't get why you wouldn't just pay the friggin' $80 or whatever it is for a billet rod already tailored to your engine, that's already proven time & time again to be pretty damn strong & capable of supporting mondo HP numbers out of a clone.
Paying a real machinist to do the work, including mic'ing everything out, laying down prints, etc. is going to cost you what you could get a bunch of billet rods for.
(Also, that "bump" is in fact normal, as long as there really isn't any slop to match it, kind of hard to describe).
Paying a real machinist to do the work, including mic'ing everything out, laying down prints, etc. is going to cost you what you could get a bunch of billet rods for.
(Also, that "bump" is in fact normal, as long as there really isn't any slop to match it, kind of hard to describe).
ditto that. i imagine that just using dimensions of the
custom connecting rod without taking into account
the material science of metal you choose to make it
with would result in a poor component lifetime.
given that, buy a chunk of aluminum and make a
connecting rod. lets' see how it works!
:thumbsup::thumbsup:
phil
custom connecting rod without taking into account
the material science of metal you choose to make it
with would result in a poor component lifetime.
given that, buy a chunk of aluminum and make a
connecting rod. lets' see how it works!
:thumbsup::thumbsup:
phil
You've made the best decision you could have.
$85 is cheap insurance. :thumbsup:
(I've also toyed with the thought of machining a connecting rod out of 4140 for a few "junk" engines I have just to muck around with the idea. I imagine it would unbalance the poor thing, but it may not provided the design was sound... and would support wickedly high revs.
)
$85 is cheap insurance. :thumbsup:
(I've also toyed with the thought of machining a connecting rod out of 4140 for a few "junk" engines I have just to muck around with the idea. I imagine it would unbalance the poor thing, but it may not provided the design was sound... and would support wickedly high revs.
)
I guess my posts were in this thread.
http://www.oldminibikes.com/forum/honda-clone-predator-engines/92465-rod-bearings-2.html
http://www.oldminibikes.com/forum/honda-clone-predator-engines/92465-rod-bearings-2.html