Block Tumbler Help

[Adam C]

Anyone have any tips on a block tumbler? I bought the block buster from Model Expo and tested it on some junk blocks, but when I put a couple of Chuck’s internally stropped blocks in, it ripped them to shreds. I tried a bunch of different angles and techniques, but it started to destroy the paddles too. blocks get jammed between the paddles and the sides and either the block or the paddle breaks. What on earth and I doing wrong? 

[Dziadeczek]

Sandpaper too coarse?

Edited February 18 by Dziadeczek

[Chuck]

Probably too coarse(I use 320 grit)....but more than anything you are not gluing up those layers securely with enough glue...and or not waiting long enough for the layers to completely dry.  Dont be afraid to use enough glue.   In my case usually CA.   A drop on each area needed to be secured.  And I tumble at the highest speed in my tumbler...3000 RPM.  Note how my tumbler is home made and very simple.  No wood flapper and instead just a few sheets of 320 grit which are very flexible yet stiff enough to do the job.

 

the center shaft is also simple…a wooden stick (cherry) with a slit in it to accept the sandpaper.  Like a tuning fork of sorts with some cross strips in the center to prevent splitting.  
 

This thing gets a ton of use and does the trick beautifully without any broken bits afterwards.

 

 

[Adam C]

Thank you both! The support on this forum is incredible, when even the guy who makes the blocks is there to help! 
 

I’m going to try and modify it to get rid of the paddles like Chuck’s. Even when I threw in normal blocks it jammed them against the sides and chipped the paddles.

 

Sir, you’ve got another block order coming tonight. Let’s try this again!

[robert952]

Us lurkers like this kind of thread, too.  Thanks for posting. 

[Chuck Seiler]

Chuck,

    What did you use as a container?

[Dr PR]

I made a simple device to round the edges of blocks. It worked fine on Chuck's blocks:

 

https://modelshipworld.com/topic/19611-albatros-by-dr-pr-mantua-scale-148-revenue-cutter-kitbash-about-1815/?do=findComment&comment=981060

 

 

I used SIG SIG-Bond aliphatic resin model airplane glue and was careful to get glue on every mating surface. I let them set over night and then tumbled them. For times and results see the link.

 

Edited February 20 by Dr PR

[Chuck]

7 hours ago, Chuck Seiler said:

    What did you use as a container?

I bought a case of metal cans with a screw top.  It cost me $15.  They are the size of a can of peanuts give or take. 
 

Folks use them to make candles or to store candy and other stuff.  Got them on Etsy.  I thought I would need many and I would wreck them after a while but this is still the first one after about 6 years.

 

Chuck

[Adam C]

Based on y’all’s feedback, I ended up modifying my block sander with 320 grit and replaced the paddles with sandpaper. I just stapled a double ply to the center mandrel. Worked like a charm! Chuck’s blocks came out looking incredible. 
 

[Dr PR]

Very nice. You used a lot finer grit than I did (80 grit) and got the same results. So I looks like it doesn't matter much what type of sandpaper you use. How long did you tumble them?

Edited February 27 by Dr PR

[hornet]

Mine is made of a piece of poly pipe with 2 end caps. It has a four bladed sandpaper impeller. Fitted with a motor that is hooked up to a variable speed switch box. 

[robert952]

16 hours ago, Dr PR said:

Very nice. You used a lot finer grit than I did (100 grit) and got the same results. So I looks like it doesn't matter much what type of sandpaper you use. How long did you tumble them?

And at what speed?  

Rock tumblers run about 30 RPM. It would seem that using a drill you'd get a lot higher speed.   (I like the small speed control motor idea @hornet uses.)

[Dr PR]

With my cobbled together tumbler I just ran the drill at "medium" speed - whatever that is. It is a hand drill with a variable speed "trigger" and a set screw to set the speed. I can lock it on so I don't have to sit there pulling the trigger. I let it run for 8 to 12 minutes (longer for larger blocks).

[Adam C]

I ran it at a pretty high speed. I don’t know what my drill goes up to, but I just held it at wide open for about 30 second increments. Took maybe two or three minutes total.