Economics of transmission
 

On Sep 26, 12:32*am, "Michael Koblic" wrote:
I am not sure if I am going crazy or the world around me is:

I am going around trying to price out a project: To reduce motor speed using
a pulley system by 16:1 would cost me in pulleys alone $50 using a local
supplier (2 6" and 2 1.5" pulley). I have just come back from an auction
where one could buy several drill pressess for around $40. For this I have
two step pulleys, a motor, a shaft, some bearings etc.

Since when has it become cheaper to buy an assembled piece of second-hand
equipment and cannibalize it for parts rather than buy parts alone? Come to
think of it, it would not even have to be second-hand equipment: Plenty of
cheap small drill presses for $100, i.e. a cost of 2 step-pulleys alone.
BTW a single sleeve 1/2" bearing - $5.00.

Is this an atypical observation? Is this a common phenomenon in the USA
also?
Michael Koblic,

It's time vs money. You can buy new parts with known specs that all
fit together and have the machine running quickly, or rebore pulleys
and machine adapters for used stuff that may be too weak or damaged.
When I build or repair a machine for industry I buy new to get the job
done quickly. Second-hand parts are usually too risky for production
machines though they may go into lab prototypes.

At home it's reversed, I adapt used stuff whenever possible except for
important equipment like the vehicles and household plumbing or
wiring. You have to consider your time and the likelihood and
consequences of a failure. If this polishing machine (?) breaks down
and makes you miss a delivery deadline then you could lose more than
the $50.

The shaft, bearings and pulleys for my sawmill cost over $100 new. The
mockup for the transmission was made from cheap used parts but when I
calculated the torques for 5HP I realized I had to buy larger shafting
and new steel pulleys.

Be glad you aren't buying new hydraulic components.

Jim Wilkins