Home made drum sander -what are component change dangers?

[Jaager]

I have a drum sander made using plans from the guild - probably from the 1970's

I use it now for 60-80 grit  to get two clear smooth surfaces -  my bandsaw slices need ~0.045" planed on each surface for scar and wander removal.

 

The old motor - a 1/3 HP cap. start finally died - I was a bad daddy = poor vent closed box - did not see the ocean of saw dust that was haft way up the motor.

 

I have replaced it with a new Granger  1/2 HP 1700 rpm TEFC GP no cap. and I cut large holes in each side for air flow.  It works really well.

The new 1/2HP has a 5/8" shaft instead of a 1/2".  I bought a new 4: x 5/8" pulley that got here the same day as the new motor.

 

I do not have room for an actual planer -  It would be that or my car in the garage.  The constant salt air - not good for a car.

 

Now I want to tempt Fate.

The drum is 3" x 11"  Hard Maple -  it is showing cracks -  way back when 9x11 paper was it and this drum fits that exactly.

I use Weldwood Contact cement to hold the medium.  Even though I now use cloth backed medium, it is still a chore to replace - nothing that I have tried will dissolve the contact cement.  Mineral spirits and Naptha will kill it and turn it into sticky balls, but it is work to clean.

 

I can get an Aluminum rod - custom cut to 11" -  3"  but I thick I want to get a 4" diameter.

The increase in diameter will increase the area per unit time of sandpaper at a given RPM.  Should be OK for the new motor I think.

If I leave the pillow blocks where they are - I will lose 1/2" of stock thickness.

My drum has a 6" pulley

My motor has a 4" pulley

This means that the drum is rotating 66%  of the motor.

 

 

If I get a 4" Al drum - custom cut to 11"  from MetalsDepot,

I found a 1/2" steel  keyed rotary shaft at M-C ,

If I get two 6" wedges from MM  -  with a wedge mechanical paper hold like Jim's design - paper change will be easy.

If I raise the pillow blocks to be able to sand thicker stock,  I can keep my present belt if I replace the 6" drum pulley with the 4" pulley from my old motor.

I will get an additional 1.75" of possible stock thickness

 

I just need a local shop to dill a 1/2" hole down the center of the AL rod.  Mill a key way into the inside hole to connect the shaft to the drum - partway at one or either end should do the trick?  Mill a wedge slot and tap for 4 holes.  I figure that trimming 1/4" from each end of the two 6" wedges should be no problem?

 

 

Now the question:

Will increasing the drum circumference from 9.4" to 12.5" and increasing the RPM of the drum from 1100 RPM to 1700 RPM  -  thus increasing the area of sanding medium per unit time cause a problem?

If it does, I guess I can get a larger diameter drum pulley and try to find a new belt that fits.

 

I am of a hope that I will find out Tuesday if I can find a local shop to mill the Aluminum and if the cost is acceptable.

I really would like to surface my rough 8x4 by 2 foot Maple and Cherry to play nicer with my bandsaw,

 

[Altduck]

6 hours ago, Jaager said:

Now the question:

Will increasing the drum circumference from 9.4" to 12.5" and increasing the RPM of the drum from 1100 RPM to 1700 RPM  -  thus increasing the area of sanding medium per unit time cause a problem?

This would increases the surface speed from about 2,700 to about 5560 Ft/minute; will heat be a problem?

[Jaager]

1 hour ago, Altduck said:

This would increases the surface speed from about 2,700 to about 5560 Ft/minute; will heat be a problem?

That is the factor that concerns me.  I see a balance  between the friction and the contact time being half and the longer trip around the drum allowing for more cooling.  

If the fabricator can and will do it, and does not want a king's ransom I guess I will just try it and see.   If heat is a problem, I can fit a larger pulley on the drum and take the machine to a local belt supplier and get the correct new belt.

 

I see a challenge feeding a two foot plank that is 2" thick and 7-8" wide.  It weighs a lot more than a 1/3" slice.

 

Bandsaw observation:

The 2x4 framing timber slices are a lot straighter than a fuzzy cupped hardwood plank allows.   

The blade seems to cut straighter if the convex side is on the table.

[Rik Thistle]

Jagger,

 

A 4" dia piece of Aluminium rotating at a possibly higher rpm will contain a lot more energy than the previous (lighter) wooden block. You'd really need to make sure any bearings, support structures, cooling etc  were up to the task.  I'd tread carefully....not saying it wouldn't work but be wary.

 

Richard

 

[bruce d]

Out of curiosity, why change to aluminium?

[Jaager]

The cooling  - new motor - now TEFC - and wide open cross ventilation because I cut away the two sides of the box.

The 1/2 HP is powerful enough I think. 

The old pillow bearings may not stand up to twice the RPM.  I will watch.  And probably opt for a new belt and keep the 4" drum pulley if I decide to increase the axle height. 

 

Same UCP pillow block  =  $10 vs $17 vs $23 on line -  the serious ones have grease fittings - and I left my grease gun back in KY with my John Deere.

A small gun for 3oz cart not too expensive

 

This is getting more and more involved - 

 

 

1 hour ago, Rik Thistle said:

A 4" dia piece of Aluminium rotating at a possibly higher rpm will contain a lot more energy than the previous (lighter) wooden block.

I had been thinking that Maple was fairly dense,  but my back of the envelope calculations 

s.g.  Map 0.71   Al  2.7

3" = 1.5 squared   4" =  2 squared   pi and length cancel -   2.25x0.71  vs 4x2.7 =  1.6 vs 10.8  = 6.75 times heavier  WOW

 

Every time I approach building a new hull, I forget just how much time and work are involved in getting enough framing stock.

At 1:60 scale  I am estimating that I will need  60 x 2' x 2"  for a 3rd rate    and 100 x 2' x 2"  for a 1st rate for framing stock

The wood needed for everything else is trivial in comparison.

I don't think scratch POF is feasible if you are not your own sawmill.

 

[Jaager]

58 minutes ago, bruce d said:

Out of curiosity, why change to aluminium?

Mostly for the ability to clamp the sandpaper instead of using glue.

 

 

Plus - the Maple is no longer a uniform diameter -  not a serious problem when its job is to get bandsaw slices to 80 grit surfaced stock that is close to final thickness to finish using my Byrnes unit for 150 and 220. 

[Rik Thistle]

Hi Jaager,

 

That was a good weight comparison you did....it surprised me too that it was almost 7x.

 

So you are dealing with a significant increase in kinetic energy. That, plus adding a new motor would tend to push me towards trying to find an existing, off-the-shelf solution that has been design tested by the manufacturers and then many users.

 

I know you are tight for space, but I would avoid tempting Fate at all costs 😉

 

Richard

[bruce d]

4 hours ago, Jaager said:

Mostly for the ability to clamp the sandpaper instead of using glue.

 

Have you considered aluminium thick wall tubing?  That will keep the mass down.

[Jaager]

30 minutes ago, bruce d said:

Have you considered aluminium thick wall tubing?  That will keep the mass down.

Then there is a new problem - getting a 1/2" steel shaft fixed dead center in the long axis.

 

I am of the thought that 7x not very heavy is still not very heavy - at least  as far as a 1/2HP motor is concerned.

 

 

4 hours ago, Rik Thistle said:

I know you are tight for space, but I would avoid tempting Fate at all costs

I will still have the old parts.  I can recover what I now have.

I will do search for commercial drum sanders.  My prejudice/supposition going in is that there are model size sanders -  and then there are commercial shop size.  I am guessing that the middle belongs to bench top cutting planers.  I will explore.

 

 

 

[Roger Pellett]

Dean,  

 

Price points:  

 

Dewalt portable planer.  Mine is mounted atop a plywood box with castors. I move it outdoors for planing it’s very noisy and can quickly make a wheel barrow load of shavings.  Capacity about 1in.  Cost $500 +-.  Corrosion- Store In plastic snap on lid box w/ zrust.  Space- not much larger than what you have.

 

Byrnes sander-  Enough already said;  if Company resumes production. Cost $650?

 

Full sized drum sander: $1500 and large.

 

Improving what you have:  The speed issue should be easily solved by swapping out the pulley combination.  I would swap out the bearings with new ball or roller bearings.  These are not expensive.  So, it is certainly possible to upgrade what you have.  The question is cost.  I doubt if any custom machine s hop can machine the shaft and drum for anything close to the $500 spent on a small portable planer.

 

Roger

[Jaager]

1 hour ago, Roger Pellett said:

 Capacity about 1in.  Cost $500 +-.

My stock is 2 in.    But serious food for thought.  Looking on-line 12"  is more than wide enough,  most seem to accept 6" thick and 3" is the most that I will need. 

 

1 hour ago, Roger Pellett said:

The question is cost.  I doubt if any custom machine s hop can machine the shaft and drum for anything close to the $500 spent on a small portable planer.

If I am reading you correctly,  the Aluminum milling will be too expensive?

It is beginning to look like there is more to this than appears at first glance,

 

I have a Ryobi 10" tables saw system - it will mount a router under the table - extra surface on either side of the blade- it is on wheels -  The table saw works  but I would rather not use it - I like having 10 fingers - plus the blade kerf and limited depth of cut per pass does not compare to my bandsaw for milling.  Right now, it is a table that holds my scroll saw and parks my sander off my work bench.  Now that I think on it,  I guess that I could park a CRAFTSMAN 12.25-in W 15-Amp Benchtop Planer ( favorable review and is $350 at SLowes -  65 lb)  on it and play musical chairs with the other tools.    Move it out to my driveway for use. 

 

[Roger Pellett]

I would assume that machining your Aluminim bar would also require turning of the drum  to get concentricity with the shaft and to remove the as delivered tolerance on the aluminum bar.  While you can probably order different grades you need tolerances in the thousands, not hundreds. You would want both ends of the cylinder faced off square to minimize vibrations of the rotating mass.  

 

Roger

[Jaager]

Drilling down the center for the axle.

I propose to use a 1/2" steel rod with a key way already cut into it for the axle.

The drum would need two matching key way slots - one at either end to mate with the axle slot.  ?A 1/2" or so deep slot - enough for an off the shelf key?

I do not think a glue bond would be wise and I understand that Al to Fe welds do not work.

Then the drum would need to be trued and polished a bit.

Then a slot milled on the long axis  to match the wedges on the Byrnes sander and four tapped holes.

I guess truing the ends too.

 

Something like six separate operations -

Edited December 4, 2023 by Jaager

[Jaager]

Up date:

 

For my rough 8x4 - I now have a Craftsman benchtop planer.  It said to use a jointer, but it smoothed out the minor cupping -  I took 1/32" passes - several of them -  Still did not fix the horrible 2" faces, but the 6-8" faces are as clear as I wish - I am happy with it.  I have room to park it on my Ryobi BT3000 table.   I think that I can place it in the middle and plane stock where it is.  It is no fun to move.

I tried a 2" straight bit on an under the table Wen router, but the guide setup was beyond me so that was a mess. 

I plan to try mounting a 3" drum and doing multiple passes.  I have a speed control box - a rheostat I think - the question is - will the motor have any torque at the 1700 rpm range that the sanding drum requires?

 

One of the 2' Maple 8x4 stock had a branch root or something irregular and my bandsaw blade did a bit of wandering with the change in grain direction.  It will be touch and go to get 100% return to produce 0.25"  220grit stock from my initial thickness.

 

Now, moving on to my original thickness sander upgrade project.   I have new pillow blocks and shaft collars.  I have an 18" x 1/2" shaft with a key way.  And  the 4" x 11" Al cylinder is here.  Boy am I surprised at how heavy it is.   It worries me a bit about the work on the motor to move that thing.  But, it has to turn it, not lift it - there will be a lot more momentum.   I was just notified that the 6" wedges will be here on Monday, so everything needed is almost here.

The local fabrication shop says they will treat me fairly.  I think I will wait out the season before I do my visit.

 

Cutting a big hole on each side of the box was a really good idea.  The motor does not get too hot.  Now I wear out before the motor.  The old one had a thermal switch and it stopped after an hour or so.