Possible bent crankshaft?

Hello briar members,

I have been working to get a letterpress machine running for a few months and have just run into a potentially serious issue. The smaller flywheel rotation is slightly off. The wheel shifts ever so slightly on the axis each revolution (no more than 1/8”).

I’m wary to run the press at all until I fully understand the problem, so as to not make anything worse.

You can see (and hear) the issue here: http://youtu.be/H3gitsRB6j4

Press information: 12”x18” C&P New Style, motor operated. Very well oiled.

What are your thoughts? Solutions?

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Can’t tell real well from your brief video. The camera moves too much. I don’t think you have a big problem. You have a wobble. The size of the flywheel amplifies the wobble.
You should determine how true the shaft runs. It will not run perfectly true. The machine is old and there is some wear in the bearings.
If the flywheel is not mounted exactly true and concentric with the shaft, it will amplify the apparent problem.
It would be good to have a dial indicator, but if you do not have one and know how to use it, you can do as the old pressman did.
With great care put a long screwdriver or metal rod on the shaft at the bearing where it exits the frame. With the press turning and with GREAT CARE, put the other end in your ear. You are listening for any grinding or thump sounds. You don’t want to hear any.
Next and again with GREAT CARE, hold a screwdriver in the vertical position with the tip on the shaft as it exits the bearing. The screwdriver will move up and down a small amount as the bearing has some wear. Shouldn’t be a great amount.
I think you will be good to print. Keep the bearings on both sides well oiled.
I was taught that if there is not some oil on the floor, you were not oiling enough. Oil is cheap. Wear is bad.
Get some ink on your shirt.

Note that this is not a flywheel — it’s just a flatbelt pulley. You mention that the press is motorized, but not how the power is getting from the motor to the press — maybe a belt around the flywheel (which is the big, heavy wheel on the left of the press)? If you were powering the press from the pulley on the right side, especially with a flat belt, the wobble might be an problem if it tended to throw the belt off, but if not being used to power the press, it’s not an issue (and you could remove the pulley if you like). As Inky mentions, it would be good to check the bearing for wear and the shaft for straightness, but it may be just the pulley that’s a bit “off.”

Dave - the motor powers the press via a leather belt on the flat belt pulley.

The wobble does not throw the belt off. It does cause a nasty grinding sound that amplifies with the speed of the rotation.

Grinding sound is not so good…

Whatever bent the pulley may have pushed the crankshaft toward the left side of the press (such that a rough spot or the bend is running in a journal). I’d see if the crankshaft has play left to right and if it can be moved and affixed back to the right. It might run freely in that manner.


I came across a C&P the made a grinding/screeching because one crankshaft bearing was installed upside-down and was not getting oiled. I’d check for that too.

Ladybird, as has been suggested, but not followed through completely!! It would be normal and almost a must for any shaft, that traverses the machine laterally, (wether it be a straight shaft or, the crankshaft with the crank pin, in the middle) TO BE HELD LATERALLY by 2 plain collars immediately inboard of the main frame, side stanchions, normally, only anchored, with 1 or two grub screws, usually more than enough, but if as is possible, the machine has been either dropped, onto the lopsided heavy flywheel, or encountered an immovable object on delivery, one or either retaining collar(s) have shifted even/only 1/8” of an inch, the mainshaft can and may well wobble laterally by that amount? and you will surely find that, on the opposite side, that same shaft, carries at least one cog, to mesh with the main drive train, should that be happening you may well get, one of 2 possible effects, i.e. one cog is running out of line, and rubbing the main frame, hence the grinding noise, OR as the machine has seen a lot of service over many years, the cogs and the teeth thereon, wear in a particular way and not always exactly tooth for tooth, i.e. if/when some mishap occurs, and it is not uncommon, as the wear that has built up over a long time only has to be slightly out of sync. laterally and the little unworn extremities, (like needle points) are trying to run in the worn (valleys) of the corresponding gear(s) or vice versa, again Grinding Noises… Possibly quick check, machine turned by hand, and a second pair of hands putting slight side pressure on either end of the shaft, excessive/unusual, lateral movement could/should be felt and seen..
All, Just possibilities. . Apologies for rubbish.!! Good Luck.

AnonyMouse - thanks for the tips, I’ll check those and report back

Mick - I appreciate the comment, though I don’t understand your suggestions completely.. I’ll check the retaining collars and report back. Cheers.

Apologies, my efforts were based on current repairs to an English Adana T.P. 48 (small floor standing platen) with exactly the same problem, in essence, the Flywheel was wobbling and the shaft had a slight bend, I suspect dropped by a previous owner, there was side play on the (main) shaft by at least 1/8”. In this case because, in the presumed accident, one aligning side thrust collar, HAD BEEN, forced along the shaft, allowing the wobble and more importantly putting the driving and driven cogs, on the opposite side to run out of line, not seriously, but audible and annoying.!
Resorted to replacing the shaft, fortunately 1” diameter quality steel, just had to machine 3 slots for key-ways.!

The foregoing only based, on current Adana repair, but there appears to be, the same basic arrangement, in machines with outboard mounted, flywheel wether treadle and crank, or motorized. . N.B. conjecture only, Not facts, with apologies.

As your clip shows the flywheel ,with visible gap between it and the main frame, there may be no lateral retaining collars, but the shaft kept in its correct alignment, with cog(s) being close, on either side of the mainframe(s) with side *thrust* washers, BUT still possibly disturbed one side or the other, if there has been a prior mishap, still possibly check for side play, would expect to see no more than 1/16”. . My best shot, albeit crude. Good Luck.!!!

I removed the ‘flatbelt pulley wheel’ and took two more videos - hopefully these will “shed more light” on the issue for someone?



Pure guess, (nothing more) the shaft is possibly, bent, outwards of the main frame but behind the small pinion, *A* from the wobble in the first shot on the flywheel.!! and *B* from the noise of 2 gears rubbing together in a very inconsistent manner.
Suggest possibly (with extra pair of hands and safely) turn the machine by hand, observe line of sight, on the small pinion and during 360 degree revolution, is it meshing consistently OR, the gap between the pinnacle of one tooth and the valley opposite, (male/female syndrome,) visibly varying.
If it looks suspicious, double check by slowly & gently turning by hand with a probe or spill of 1, 2, 3, or 4 thicknesses of paper, >progressively< wound round between the teeth, progressive thickness,es of course, if the problem is as suggested, the teeth will cut the spill at the point of most contact, and probably leave a visible gap at 180 Degrees.!! In the event that this test eliminates the problem from the fly wheel side, is there a duplicate gear train on the other side of the machine, needing in depth investigation.??
As treadle & crank have been specified, and the shaft has to be steel rather than cast, it would have almost certainly snapped, if the later.???
As treadle machines, Usually by the nature of there construction have to have at least one shaft bearing, carried in removable *Boss* usually, PEAR, shaped to withdraw the crank shaft and crank pin, it is not easy to remove the crank, but not insurmountable with patience.

Possibly remove the crank and have it straightened, by a reasonably proficient engineer with hydraulic press and 2 *V* blocks, reasonably common occurrence here, U.K.

My best GUESStimate, apologies for a potential load of “that stuff” but Good Luck, anyway. Mick.

P.S. (Non intended) but high-flying *ACE* cameraman you aint!!!… Ancient Limey sense of humour, as we say here if wit was **, I would be covered, *have A nice Day*

The 2nd video shows that the bad noise happens once every revolution of the main shaft. I would look closely at the teeth on the small pinion gear and see if they are OK. If need be, clean all the grease and oil out of the gears and inspect closely for chipped, broken or bent teeth on the small gear.

Also you can take feeler gauges and check for the amount of backlash,(clearance between gears) at different points of rotation. These should be fairly constant, a jump either way at the point of noise will indicate the the next step in troubleshooting.

A dial indicator on end of shaft will tell if it is bent or not. It does not appear to be bent from the video.

One of the unwritten rules of machine design is that you never design a gear train with an even number gear ratio.
For instance, you would design a gear set that has a 13/48 ratio vs a 12/48. The advantage of the odd ratio is that the gear teeth do not mate with the same teeth on the other gear all the time. The teeth with a odd ratio have to mate with all the teeth of the other gear before they mesh with the first combination. This evens out the wear on the gear teeth.

What this has to do with your press is that since there is probably an odd ratio on the gear ratio and the noise becomes noticeable at the same position on the main shaft, the problem is in the main shaft and not the larger gear. This at least should narrow down the troubleshooting.

Armchair quarterback troubleshooting. With the narrow time span of the noise I would be more inclined to think gear teeth problems vs. bent shaft.

Keep us posted. We all love a good mystery and the finial “Who done it” ending.


The noise has the same period as the crankshaft rotation. I’d make certain the teeth on the pinion are free of packed dirt/grime, and repeat the close-up shots, using a tripod/brace as Mick suggests.

The pulley is likely bent. I’d confirm by putting it on a true shaft and spinning.

In the third video, it looks like the shaft is jumping up and down at times. If you grab a hold of the end of the shaft, does it wiggle up and down to some degree?

I am parting out this press if anyone is interested, please message me.


One question. Has the flywheel and shaft been out of the press lately? Say, to move the press, etc.
Winfred Reed
Black Diamond Press (Kentucky)

Hi Winfred,

No the flywheel and shaft have not been removed to my knowledge.

Thanks for taking the time to answer my question, I’m happy to take the time to read the discussion and watch the videos about your question, only to be ignored. If you need me I’ll be in the corner flailing madly at my keyboard. It’s a bit like a infinite number of monkeys in a forest when no one is around.

Hey Keelan,

I’ll try to remember to check this next time I’m at my shop. What will this tell you?

^That could indicate a bad bearing and/or worn shaft.

I took apart an 8x12 last week… It took less than an hour to remove the crankshaft.

I would take the pinion gear off the crankshaft and measure the radial runout with a dial gauge - quite easy to do and the gauge/holder are not expensive.

If the shaft is bent: As Mick points out, a decent machine shop can straighten the shaft (likely for less than a Benjamin).

i would suspect/ inspect for bent/ damaged teeth on the pinion. there is nowhere Near the “run-out” at the end of the shaft to cause that much noise.
Damage: from foreign object entering the :mesh” area.
Bent: from solving a major “lock-up” improperly.