Arbor press tonnage ratings

[LD1]

Not really a good forum to post this in.....and not a member of anywhere else that may yield better answers....but figure with many people here someone might know.

Here is the dilema. I have a Famco #2 arbor press....rated at 2 tons, and a 35:1 leverage ratio.
Also have a famco 3-1/2R arbor press rated at 5 tons and 70:1 leverage ratio

The job is punching some sheet metal holes. And to my surprise, the smaller famco #2 punches just as easy as the larger.....3-1/2r which is supposed to have 2-1/2 times the force.

So started doing some digging of just how they come up with their leverage ratios and force calculations and all that.

the smaller famco has a pitch radius of 0.70 and a lever arm of 24.....which calculates pretty close to the 35:1 leverage ratio. Meaning that 114# hanging on its 24" arm should yield the 2-ton claimed. And I have no doubt that it does just that.

However, the 3-1/2R only has a 1" pitch radius, and a 35" arm.

So how in the world are they coming up with a 70:1 leverage ratio.

To get 5-ton rating....at 70:1....should only need 142# hanging from its 35" arm....which is very attainable. But in reality.....I am only getting a 35:1 ratio.....even with the longer arm. Meaning its no stronger than the small benchtop famco #2???

So what gives? I know this is an older press. did it originally have a 70" handle???(which would seem odd)? Dont really know how someone would change the pitch diameter. everything looks original?

Is this just a case of marketing gimmicks like everything else that ratings are bogus on...like logsplitter tonnage, etc?

 

[CincyFlyer]

I used to sell industrial machinery. If you larger press is older, it may have had an additional reduction gear set; some of these could be removed, and were, leaving you with about 1/2 tonnage.

 

[LD1]

Don't really see where anything could have been removed.

And it's not listed as a compound racheting either. Looks identical to what's on their site now.

 

[LD1]

 

[HarryVanderpool]

The tonnage has nothing to do with the work load or effort.
The rating is the maximum force that the arbor press frame can withstand and not deflect.

 

[bcp]

Beat me to it.

See tonnage ratings, ratios, and weights about halfway down this page.

Single Lever Arbor Press 1 | Dake Corp

Bruce

 

[LD1]

Fair enough. But why so they claim a 70:1 leverage ratio (which would only require 140ish pounds to reach rating).....but it actually only has a 35:1 leverage ratio.

Simply put.....I cannot make it pretty any harder than the much smaller bench top #2 press....even with it's foot longer handle.

 

[bigdeano]

Maybe the larger press came with a piece of pipe to put on the handle. Like hydraulic jacks come with two piece handles.

 

[hawkeye08]

maybe one of the units has engineering information (facts) and the other has marketing information (whatever number is needed to sell the product).

 

[LD1]

Maybe the larger press came with a piece of pipe to put on the handle. Like hydraulic jacks come with two piece handles.

Actually, as per their parts list.....the 3-1/2r comes with a 32" handle....

So technically to attain 70:1 leverage ratio....the pitch radius of the pinion needs to be ~.457"......meaning that the pitch DIAMETER of the pinion would need to be LESS THAN 1" diameter.....thats nuts. Pinion shaft that small on such a large press and 32" handle would not last long.

maybe one of the units has engineering information (facts) and the other has marketing information (whatever number is needed to sell the product).

Maybe. But both from the same MFG. I e-mailed them....they couldnt give me an answer other than "we have never had any issues with the tonnage on our larger presses."

Rest assured its no where near its claimed 5t rating......and no better than a 2t bench top model.....just has a larger throat and working height is all. But NOT a stronger press as claimed.