Advice appreciated

[Dasher]

I am currently in the process of upgrading my old 4" x 48" bench sander to take 72" x 2" belts, and while waiting for some cheap sanding belts for setting up with to arrive, I thought I would throw it out for anyone to comment , good or bad , whether my system is likely to be ok or not, in the pics attached, I have stapled some 4"" sandpaper I had to make a 72" belt to get the geometry close to what I need.  My main questions are ; The vertical post is spring loaded internally, allowing a bit of give vertically, will this be ok?  The existing sander has a tension/ tracker head pulley,  do I also need an adjustable top pulley? The top pulley is adjustable now, by about 7 degs either side of centre along the line of belt, and 2 or 3 degs either side of centre horizontally at the head, as these are not idiot proof safety wise, I'm hoping they will be set and forget, once I have a belt running true, and any tracking adjustments for change of belt etc, can be handled via the existing tracking controller of the head pulley which doesn,t need hands or clothing near the moving belt. Next, with the reduced contact on the drive pulley, am I likely to get belt slip, or should I rubber line the pulley now?,  Lastly, as the motor is not enclosed/ sealed, would a light metal enclosure with a strong magnet attached reduce the entry of airborne filings, my Idea is to keep the enclosure far enough away for the magnet to have no effect on the motor field. Almost forgot, does the top pulley need to be radiused, or should flat be ok?  Thanks for reading all this, and comments, yay or nay appreciated.

[pnut]

I have never owned a 2x72 belt grinder, but I do know an unenclosed motor won't last long in a metal shop. Have you looked at other 2x72 in. Grinder designs? I've seen some here you may want to check out some of those threads.   A rubberized drive wheel sounds like a good idea to me. If my memory serves me right and it does not a lot of times I seem to recall people using larger diameter skateboard wheels to good effect but don't quote me on that definitely look into it further. Good luck and keep us posted.

Pnut

[Dasher]

Thanks Pnut, I'm just trying to make do with stuff I have laying around, the existing sander works ok, but being horizontal and waist height, it is hard to do detail work or sharpening without being in a bad posture, and these old bones complain when I do, so I figured the vertical belt section will take care of that, and it's only 5 minutes and 4 bolts and it can be set up as before as a bench sander, if it works ok, I'll keep an eye out for an enclosed motor.

[Dasher]

Update, and more questions; The belts finally arrived and I tried them out, everything runs pretty well and true, the only issue being a bit of belt "flutter" [for want of a better word] on the hypotenuse leg of the triangle, where the belt is first "pushed" from the drive pulley, given that ATM I have only tried ultra cheap ebay belts, am I over worrying about it, or do i need to add a 4th tension wheel? The working leg of the belt runs very smoothly and the vertical support is spring loaded, and I have tensioned it to what I guess and feel is about right, I'm hesitant to tighten any more without some advice from people who have been through a similar trial. Thanks for taking the time to read, and all advice appreciated.

[picker77]

On 8/31/2019 at 2:23 AM, pnut said:

I have never owned a 2x72 belt grinder, but I do know an unenclosed motor won't last long in a metal shop.

I suppose there is an exception to every general rule, and Pnut is correct that a TEFC (totally enclosed fan cooled) motor is definitely preferred for longevity. I built the pictured 2x72 grinder in 2006. The motor is a non-enclosed 1.5 HP 120V 3450 RPM capacitor-start fan motor rescued from the attic when we had our central A/C replaced back in 1996. The shaft drive wheel is 4" diameter and rubber covered, the tracking wheel was recently replaced with one from OriginBladeMaker, and my original skateboard wheel platen setup (which never worked well) has been upgraded to OBM's nicely machined platen/wheels, which run smooth and true. Every few months I suck the grinder crap as best I can from inside the motor with a large shop vac, and blow it out with the shop air hose, but that's been it for maintenance for the past 13 years. I used it daily and pretty hard, and it still runs just fine. Because I really would like to have speed control, I'm getting ready to upgrade with a VFD and a new 2HP 3-phase TEFC motor. I also have an accessory tool arm with an 8" rubber covered contact wheel that works really well. I guess my point is don't hesitate to at least temporarily make use of a non-enclosed motor if that's what you have and cost is a factor at the moment. You can always upgrade later as funds permit. That's what worked out best for me.

[Dasher]

Thanks  picker77, I've got it running and tracking well atm, haven't made a lot of dust due to other things needing doing, but I' ll run it as is for a while and keep up the maintenance like you noted, if it lasts 1/2 of 13 years they can put it on my coffin.

[picker77]

Sounds like me, I'll be 78 next month, I'll have to leave instructions for the wife to make sure she doesn't yard-sale this grinder for $30. Looks like you have a great setup for slack-belt grinding. I'll bet you will also eventually want to add a removable tool arm holder of some sort, so you can run home brew tool arms with a platen and a contact wheel one of these days. Neither are hard to add, the tool arm/contact wheel was easy, but from my experience I recommend purchasing a professionally fabricated platen/wheel setup from the outset. I initially made a platen using skateboard wheels and it worked OK most of the time, but wheel alignment on a platen needs to be perfect, and my "precision" home shop fabrication/assembly tolerances (add one more washer here or there, lol) resulted in intermittent tracking problems, depending on which side of the belt I put pressure on. After I was making knives more often I finally bit the bullet for the real deal, and it runs smooth as silk. Very well spent $90.

BTW, in 1978, when the Navy was scheduling my next duty transfer after three years in Hawaii, they offered to send me on a 3-year assignment to the USN communications facility near Perth. But with two boys in high school at the time I opted to go to the U.S. east coast for my final tour before retirement (I retired the first of three times in 1980). I think I would have enjoyed a down under tour, have always liked Oz folks, they are salt-of-the-earth type people.  G'day and enjoy the grinder!

[Dasher]

Thanks  picker77, yes I think I will need to sort some time of platten arrangement eventually . BTW  that communications facility you mention "near Perth" is almost 1/2 way up the state, over 700 miles from Perth.

[ThomasPowers]

From 10K Miles away they look almost next door!

[Frosty]

10 hours ago, picker77 said:

I'll have to leave instructions for the wife to make sure she doesn't yard-sale this grinder for $30.

Well, so much for attending YOUR estate sale. 

I don't know what Deb'll sell my stuff for if I go first, she keeps talking about having a yard sale to make more room for things she want's space for. 

Frosty The Lucky.

[picker77]

Dasher, you're right. It's called Northwest Cape for a reason, ha. Technically, I think I would have enjoyed the job (Electronics Maintenance Officer), but boy, it's definitely out in the sticks.

Frosty, I've already told my two sons to bring U-Hauls behind their trucks when they come to the funeral.

[Dasher]

Well  picker77 I applied for a job there in the early 80,s, doing maintainence on the towers, I missed out, in hindsight, luckily, I, ve already had 1 knee and 1 hip replaced, and another hip being done soon. I think had I been climbing 1000' towers all these years  Í' d be on my 2nd or 3rd set of hips and knees by now.