Grinder design questions: tracking wheel & drive wheel position, over-center tension, etc.

Drew Riley said:
I’m a little late to the party here, but I figured I’d chime in. Not sure who’s seen it, but I made a vid about updating my tracking mechanism to something very similar to the Reeder idea:

Fast forward to about 3:50 to skip a bunch of rambling... also more rambling at the end. :D

The main take away (I suppose) is the simplicity of the design. Minimal material or mechanism change, and no spring needed. The belt tension is enough to keep it tight to the stops.
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Drew, thank you for posting this. I think I watched it a while ago. This is very similar to what I want to build.

You mention belt tension is enough to keep it tight to the stops, but you have a locking lever on the yaw adjustment. Is that just so it does not pivot away on its own, e.g., when you tilt the grinder and there is no tension on the belt? That was the purpose of the spring in my design.
 
Thanks for linking the video, and for making it in the first place.
I had watched it but the other time I didn't have the sound on and assumed there was a spring I couldn't see.

I've been playing with ways to contain the aluminum chips on the miter saw and got all excited when I realized I could just get a pink pop up princess castle tent with glow in the dark stars for $17 when my wife asked why are you... followed by "oh, I've got one of those tent things for a saw at work, nobody uses it. I'll bring it for a while."
My princess dreams have been crushed.
 
I would have spent a few dollars more and gone for the rocket ship, to be honest.

I keep hitting the post reply button too soon when on my phone.
 
Not much progress this weekend, only got about a couple of hours. It felt like I spent more time setting up and cleaning up than doing actual work. I had a piece of 1/2"x8" stock that was just over 14.5" long, so I cleaned up the cut ends and made it 14.5" even. That will be the base plate. I also got a start on a couple of hinge pieces. They will get rounded over eventually and the front one will have a slot in it for locking the grinder in the horizontal or vertical position. They have press fit bushings and are bolted to the frame with a long bolt through both side pieces and the tool bar spacers. The 3/4" aluminum I used looks way too thick. Maybe that will improve once the pieces are rounded and chamfered a bit.

tBYSfC9.jpg
 
Hubert S. said:
Drew, thank you for posting this. I think I watched it a while ago. This is very similar to what I want to build.

You mention belt tension is enough to keep it tight to the stops, but you have a locking lever on the yaw adjustment. Is that just so it does not pivot away on its own, e.g., when you tilt the grinder and there is no tension on the belt? That was the purpose of the spring in my design.
Click to expand...

The locking lever PROBABLY isn’t necessary, but I just tighten it just in case. Honestly, I rarely even have to mess with that adjustment unless I’m running backwards on certain attachments.
 
Thank you. I have a pretty good idea now what I'm going to build. I'll report back when I find time to try it out.
 
I just watched a Kyle Royer youtube video where he is making a hammer. I think he is in Australia. At about 6:15 he is grinding the hammer and they show a close-up of the tensioning mechanism and it looks just like my cam design in reverse, i.e., pull to tension and push to loosen. It also looks like the tracking is separate from the tension arm, maybe it is on the motor like on the TW-90. Is anybody familiar with the grinder in the video? There is a logo that looks a bit like an eight or maybe a clef combined with engineering.
 
Hubert, it looks like you did the same thing I did years ago, invented something that was already invented. It does look like his tracking wheel is fixed in location in that video and would require the motor tracking setup like the TW-90. Good catch - I watched that video a while back and I missed that on the belt tensioner.
 
I have figured out that the grinder in the video is the "Gibson 72" by googling "Australian belt grinder". Not much info on it. Alec Steele sells the grinder in the US ($4,295) and has a promo video on youtube. I am excited to find out that this mechanism has been used successfully on a commercial grinder. That gives me hope that my contraption will work!
 
Hubert S. said:
I have figured out that the grinder in the video is the "Gibson 72" by googling "Australian belt grinder". Not much info on it. Alec Steele sells the grinder in the US ($4,295) and has a promo video on youtube. I am excited to find out that this mechanism has been used successfully on a commercial grinder. That gives me hope that my contraption will work!
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There is some pictures: https://www.australianbladeforums.c...4090-belt-grinders-evolved-check-product.html

it seems that the tracking system consists of changing the angle of the contact wheel
Y5bUiiT.png
 
Thank you for the link, Fernando. It looks like the whole motor and drive wheel pivot around the axis you drew in the picture.

The cam mechanism uses a small spring to apply pretension. I thought I might need one when I built the wooden prototype, but the steel cam did not seem to need it. I wonder if tilting the grinder to horizontal will change that.
 
Drew Riley said:
The locking lever PROBABLY isn’t necessary, but I just tighten it just in case. Honestly, I rarely even have to mess with that adjustment unless I’m running backwards on certain attachments.
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Hello Drew! Now I saw that you are here. I'm the guy who's bothering you asking questions on your YouTube channel. Very cool channel BTW. :thumbsup::thumbsup::thumbsup:
 
Fernando Maia said:
Hello Drew! Now I saw that you are here. I'm the guy who's bothering you asking questions on your YouTube channel. Very cool channel BTW. :thumbsup::thumbsup::thumbsup:
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Haha. No bother. If I can answer anymore questions, let me know.
 
I made the doubler plate today to attach the tracking support to the grinder. It feels rock solid. In hindsight, it would probably have been better to move the motor back a little bit and attach it to the plate on the right. I was a bit concerned because that would have shifted the tracking arm to the left by about half an inch, but now I think that would probably work just fine. Well, there is always v2.

Midwest steel is pretty slow compared to xometry. I ordered some more materials Tuesday morning and they have not shipped yet. There are a few more things I can complete before I run out of aluminum so I think it's not going to slow me down.

U1Hhskc.jpg
 
I hope midwest steel is faster shipping for you than they were for me. Took about 1-1/2 weeks for them to ship. After a week they sent email saying "we shipped" and gave tracking number. BUT, USPS only had notice a label had been created, but had not received a pkg. Took another 3 or 4 days before USPS actually got the package.

That frame is looking really solid - got a photo of other side?
 
I hope they ship a bit quicker than that so I can get it before next weekend. I have some larger pieces of aluminum that I could use to complete the grinder, but I want to save them for other projects. Tomorrow I will machine the parts for the tracking assembly. I'll take some more pictures then. I think the only picture of the other side I have at the moment is from before I cut the motor mount. It is in post 96.
 
Yeah, Midwest is about as slow as they come with processing and shipping. I normally allot at least 1-2 weeks. Their prices are pretty hard to beat though, and they don’t gouge you on shipping like others I’ve used.
 
Hubert, that photo in post #96 answered my question. When I saw it before I wasn't sure if it was final fit or not.
 
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