Carl Ijames wrote:
"stryped" wrote in message
...

On Thursday, June 18, 2015 at 12:17:07 PM UTC-5, Carl Ijames wrote:
"stryped" wrote in message
...

On Thursday, June 18, 2015 at 11:28:01 AM UTC-5, Carl Ijames wrote:
"Jim Wilkins" wrote in message ...

"stryped" wrote in message
...
I have a spare 13 horse Honda engine laying around and a need for a
vibratory compactor. My thought was to use the engine to drive a shaft
attached to two pillow block bearings. The shaft would have a piece of
square tubing or something else welded to it to create the "off
balance" effect.

Yes I know I can rent one but I need it for several different things
and not all at the same time if that makes sense.

Any ideas on the proper way to build the out of balance shaft? Such as
how much weight and how far from the centerline of the axle it should
be?

Thanks,

============

You could rent one the first time and study its design.

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HarborFreight has a 6.5 hp model,
http://www.harborfreight.com/65-hp-p...tor-69738.html, they say
5500
beats per minute and a total weight of 176 lbs. In the manual is an
exploded diagram that is probably close to scale, which makes it look
like
they step up the engine speed less than 2:1 with pulleys and two drive
belts
in parallel, and the eccentric is pretty small. They list the bearings
for
the shaft as a 6308 so that tells you the shaft size and what strength
bearings they felt it needed, the weight looks to be less than the shaft
diameter and tight to one side of the shaft. They claim 3000 lbs of
force.
Anyway, just one place to get some info.

-----
Regards,
Carl Ijames
Thanks so much. What size would you say those pulleys are?
================================================== ==================

No comment :-). If I had to guess, I would print out that page and grab
some calipers to get the ratio. Look up the 6308 bearing and use the
eccentric shaft diameter to get the scale factor, then you could estimate
the pulley diameters. If the motor runs at 3600 rpm which seems the
popular
speed for governed lawn mowers and such, and they get 5500 beats per
minute,
the step up ratio has to be 5500/3600=1.53 or just 1.5, and then just find
some pulleys to get that ratio. Read the rest of the manual to see if
they
specify the engine speed, in case my 3600 guess is wrong. It's on sale
for
$550, and you could probably sell it for over half that when you are
finally
finished ... (Just saying; I know, building is the fun part for most here.
For me it's doing the design work, I think through lots more designs than
I
ever try to build.)

-----
Regards,
Carl Ijames

Looks like a 6308 bearing is about a 1.5 inch shaft. I would have never
guess it to being that big....
================================================== ====================================

They claim 3000 lb impact force, and they do want it to survive a few
impacts. At 5500 per minute, say 1000 hours to wear out (complete guess on
my part), that's 330 million impacts. Also a great reason not to couple the
eccentric directly to the motor crankshaft :-). If you are going to step up
a little, with 16.5 vs 6.5 hp, I'd keep the speed the same and guess the
volume and center of gravity radius on the eccentric, then multiply the
radius times the volume of theirs by 16.5/6.5 to get yours. Yes, you should
convert volume to weight, but then you would just divide it right back out
:-). I'd bump the shaft cross sectional area by 16.5/6.5 as well, and use a
6300 series bearing as well. You are going to need some very good vibration
isolation mounts for that motor, too.

-----
Regards,
Carl Ijames



Usually the plate and eccentric are one item. That is then isolated from
the motor and drive assembly by isolation mounts. The one I have uses
almost the same idea as a sway bar end link. Two rubber mounts on each
end with a tube and bolt holding it together. Mounted at about a 45
degree angle.

--
Steve W.