If the steel rod is the same size as a piston pin and it slides through piston rods with very little resistance, is it safe to assume the rods are straight? The rods are fitted to the crank with .0015 clearance and they line up perfect. My question; is this a legitimate way to check the rods?
Sorry for the typo. Too stupid to proof.
Interesting low tech way to check them
Unfortunately you can't clamp the piston pin size rod with the clamping bolts since you would have needed cut outs in the rod at exact locations, so the rods won't be very precisely located by this method. Maybe if you clamp piston pins in the rods and use a thinner long rod that fits precisely into the hole through the piston pins?
How straight is the crankshaft?
Bob, that's a great piece of lateral thinking. Roger's thought about a smaller rod through the pins clamped in the rods would be more accurate. The length of the hole in the pin will mean minimal slop with a close fitting smaller bar through it. Any bend/twist in a rod would make it difficult to push the bar through a misaligned pin into the next.
I am spoiled, having picked up an aligning jig and sea lion at a clearing sale.
Allan from down under.
The inside surface of the typical rod is not a very accurate surface as well. It's a good practice to clean up burrs in that area before installing.
I suspect a feeler gauge under the pin ends is most accurate. Somebody with more experience can correct me if I'm wrong.
I see nothing wrong with this method. Should provide satisfactory results for most people.
A lot of rods have a forward/backward double offset which would not show up this way. I have never had (been able to afford) a good rod checking or straightening jig. I use several methods to check for straight, quick checks before hand fitting, final checks after fitting before final assembly. One thing I do to check for straight after the crank is bedded into the block is to assemble the rod and wrist pin into the cylinder on the crankshaft. If the rod and wrist pin are not centered in the cylinder (forward and backward), it means the rod is bent or the Babbitt was cut crooked, or both. Further alignments need to be checked to determine where the fault is, and make corrections if deemed safe to do so.
What do you feed your sea lion? Do you keep it in the backyard pool?
Neil, he doesn't eat anything at all and we don't have a backyard pool either. Now, a backyard fool is often in attendance.
Here is my rod checking jig. They come with 3 different size square mandrels to accommodate different size rods. I have this smallest size one on permanent loan from the local machine shop, them having no use for such small bearings as a T.
Here is the sea lion, or seal if you like.
With a wrist pin clamped in place, he sits on the pin this way to check bend. The two points need to contact the jig surface if the rod is straight.
Turn him around and the pins on his back flippers will show if the rod is twisted.
Now all I need is the special vice used to straighten rods and remove twists, and I have found one! Just have to convince the owner it needs to be with my jig for it to be of any use.
Allan from down under
Sure beats all my silly straight edges, steel rods, and carpenter's squares!
And measuring the wrist pin in the cylinder bore.
Gee's Wayne, If Herm was still posting, he would have a field day bagging you on your post!! let alone criticizing those who even use any other method but his!
Interesting use of square mandrels. I have & use a Stevens jig. My flywheel holding fixture is shown.
What an organized shop. Wish I could do that!
Steve, there are two advantages to square mandrels. This type of aligning jig comes with just three sizes of mandrels and these cover all rods. My machine shop has used just he middle size mandrel on car engines, having to use the larger size on on tractor and truck rods. They have never had to use the small one they have loaned me.
The second advantage is the radiused edges of he mandrels allow any size rod to sit squarely. There is no need for multiple mandrels of different sizes to suit rods with varying bores, and no need for great accuracy in sizing the mandrels.
When these jigs turn up at swap meets/sales, the first thing missing is the seal. It often gets parted from the jig and is mislaid. Because there is little/no use for the smallest mandrel these days, that goes missing too. While what I have is a great diagnostic tool, it is limited in usefulness by the lack of the separate jig/vice for making the corrections necessary.
Now to get hold of the bending/twisting jig.
Allan from down under.
Frank v E, Wouldn't bother me, I don't mind being the butt of a joke occasionally. Life has never treated me very well, and my needy crazy family has been NO help. I learned a long time ago, that I could do a lot making do with what I had or could scrounge up. I also learned that with a few decent old pieces of equipment, a bunch of old hand tools, and very careful measuring, I could nearly match a good machine shop for a lot of things I needed done. Of course, it might take me a little longer to do the job than they could do it in with the proper machine.
Understanding what needs to be square to what else, understanding the reasons things need to fit a certain way, helps a lot!
I sure do enjoy seeing all these wonderful original pieces of equipment and special jigs!