Lets build a jackshaft

S

snowplow

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[TD="width: 85%"]I need to make a jack-shaft assembly to mount a pulley on for some gear reduction. I was looking at mounted bearings like this for a starting point.



I am wondering if I can just mount one of these solid with a 4-5" shaft coming out of it that I can put a step pulley on.

I know it would be better supported if I had one on each side of the shaft. But I see lots of jackshafts like this so I am thinking it must be possible. I am thinking that if the dynamic load rating of the bearing was not exceeded by the pressure of the belts I should be good to go right?

I could also do two of these



but I think it would just be more expense and less simple.

What do you guys think? :thinking:
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The top one might work if you keep the shaft short and the pulley in very close to the bearing face. Diameter of shaft has a lot to do with it also along with the amount of force used the tighten the chain or belt used between the 2 pulleys.

The second one has to be used in 2's as the bearing swivels in them.
 
Hi Dustin,
I dont think your 1st idea would work. Unless the drive pulley and driven pulley are exactly loaded the same and the forces are acting exactly opposite one another they would pull the shaft out of alignment. Provided that you could achieve balance, as soon as you change speeds the opposing forces will change as the fulcrum point is moved.
Also what is keeping the shaft located in the bearing? Unless you have something hard up against the bearing on both sides the shaft will move axially.

Cheers Phil
 
Charley Davidson said:
The bearings have set screws in them
Click to expand...

Ok, I didnt take note of that before.

Charley Davidson said:
You could just put the flat mount bearings back to back on the mounting plate:thinking:
Click to expand...

I would still be concerned about the amount of leverage you will get 4-5" out form the bearing. Snowplow did say he wanted to try and get away with just 1. If you were going to go with 2 then the ideal placement would be at either end of the shaft with the pulleys in between.

Cheers Phil
 
As I read this I had a flash, about #1 I have a freebee wood chipper shredder this bearing about 4''
square like #1 I think the shaft could be 5/8 anyways talk about a load, incredible weight that flywheel
has. Just food for thought. although I would go with two bearings
 
Most flange blocks as shown in your first photo, are spherical outer race for self alignment. They are not suitable to use as you describe. Also, a cantilevered (overhung) load on a single row of balls is a design no-no.

Regards
Bob
 
another option would be to mount a solid shaft to a bracket, and have bearings in the pulley.

mike
 
Hey thanks for all the replies guys. This is a great forum. I was super busy, sorry to leave you guys hanging.

Alright, here is the whole story.

I have a really nice older Jet wood/metal bandsaw. I picked it up for 130$ and it is in very good shape. Right now on the lowest speed it turns 186 final rpm at 682 fpm.

I cut a lot of 1/8" steel plate for my projects and think this machine would be sturdy enough for the task providing I can slow it down a bit. The tentative plan was to put a 3/4" wide blade on and slow it down by adding a jackshaft and either another set of belts or sprocket assembly.

The jackshaft I would build would probably mount to a 1/2" steel plate mounted vertically (picture a wall) so the flange mount bearings would work great. If I had to run 2 bearings I would prefer two of that style just for ease of mounting. The shaft size would probably be around 3/4" dia. Sounds like one bearing is out and thats ok, but if possible I would prefer to cantilever the shaft out (just like the factory one on the saw) to make belt changes a snap. The shaft would cantilever out past the bearing probably around 5".

I am also trying to find a good bandsaw speed chart that addresses a dry cut (for vertical machines) and mild steel if any of you know one. I have seen anything from 80-250 fpm but cant really narrow it down any further.

Hopefully that info helps see what I am trying to do. Any tips would be appreciated!

Dustin

Oh and for the record, I have a tendency to overbuild stuff. I was just trying to not go overboard on this because I am in this saw for so little. If I can keep the overall price lowish it would be a bonus. But we gotta do what we gotta do. ;)
 
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