I'm working on a conveyer belt project for some side work. I have a simple problem, and I cant come up with a solution. At this point I'm just wasting time.
I'm copying the customers existing system. They turn the bolt, and the green arm extends out to tension a pulley. But what stops the bolt from coming out on the left side? I could have this wrong, in that the threaded part shouldnt be welded on the green arm. Maybe it just pushes against a plate in the green arm. The force is from right to left.
It looks like the tube the arm sleeves into will limt the clevis wnough to stop it coming off the bolt head. Is the bolt head eccentric?
How about a bolt-on end cap with a double nut on the inside of the tension bolt head to push against the end cap?
Edit: something like this?
Double nut on the inside with a thrust bearing is what I'd probably do.
In reply to VolvoHeretic :
In my head I was thinking that would restrict the bolt from turning. But if you don't torque the first nut, I bet it would still allow the bolt to spin. I will try that. Thank you!
You're welcome. Keep us up to date, we require closure on these projects. 
Are you just building a tension bolt by welding a nut onto some threaded rod?
In reply to lnlogauge :
Every bolt hole should be 1/16" larger than the bolt size. Make the clearance of the jam nuts 1/16" larger also. There should also be a washer on the left side of the end plate. Don't forget to add grease to that area.
If you are worried about it unthreading once it is all assembled. If there is room in the C chanel that the threaded rod runs through, you could red lock tight a nut on the end. Or just weld a slightly larger washer on the end as a stop.
If I understand it right. The bolt is in compression. Have you seen the bolt. It could easily have a shoulder on the inside and then install from right to left, with the head protruding from the gray carrier. The green adjustable to ram you drew would work as is. Just thread the bolt into the ram first and slide the assembly in to the gray carrier. That concept kind of stinks in that you can't lock the bolt to the sleeve, so you'll lose tension with time.
It'd be better if you built it as drawn, but with a captive nut on the inside of the gray carrier, or tap the carrier itself. Then you can install a jam nut on the bolt and thread the bolt in the gray carrier. Once you find the tension you like, cinch the jam nut down.
I want to know how the tension bolt hooks onto the adjustable block bearing tube end? Is it just a nut welded into the tube?
What size of nested tubing are going to be used?
VolvoHeretic said:
I want to know how the tension bolt hooks onto the adjustable block bearing tube end? Is it just a nut welded into the tube?
Close. The bolt would just push against a face on the green part. Probably want a countersunk recess to keep the end of the bolt centered. It's not a great practice to have a bolt in compression since it's going to want to bend/walk and buckle.
As drawn, the length of exposed thread would never change as the bolt is tightened.
I have seen the bolt, it looks like an ordinary bolt. You are correct, the bolt is compression.
In reply to lnlogauge :
That's a commercial part. The entire assembly is probably commercial components.
I suspect that the threads are on the fixed part and the bolt simply pushes on the tensioner instead of threading into it.
In reply to MadScientistMatt :
It's a commercial part. The OP is asking the wrong questions. Who makes it? What's the correct part number? Where can I buy it? Is there a 3D model available? Those are the questions he needs to be asking.
Reading this thread is a bit like watching a train wreck.
I had no idea it was something I could purchase. Thank you!!!
I do appreciate the help, but I have zero experience with conveyors, and the item I have pictures of is not a purchased item. Knowing its an off the shelf item is super helpful, but calling it a trainwreck, isn't very helpful. Thank you.
In reply to lnlogauge :
Sorry. I just don't like to see people waste time and effort.
First thing an efficient engineer checks is what you can get from McMaster or MSC. Even with no part number, eventually you get a feel for something that is bought vs built. McMaster offers stainless versions, CAD, and dimensioned drawings.
https://www.mcmaster.com/products/conveyor-belt-tensioners/enclosed-conveyor-belt-tensioners/
Reminds me of a project I worked on where a talented young engineer remodelled some work car wheels in solidworks, detailed them, and assigned them a unique part number instead of a purchase part number. To have four of those wheels made cost us around $40k, and you can buy them off the shelf for under $1000/ea with an actual engineered load rating and easy to replace down the road.
In reply to 93gsxturbo :
Seems like asking on a post, and getting an answer from someone who knew the item, was a pretty efficient solution. Again, the item I have seen and have pictures of was a made item, not purchased. Tester's post was a McMaster screenshot. The McMaster item is similar enough, and will work for what I need. Seems a little ridiculous to say I should be efficient enough to know that it could be purchased.
Really don't understand the need for putting people down, but you do you I guess.
In reply to lnlogauge :
Sounds like 93gsxturbo was born with all the knowledge. Good for him.
So, we have established that the best solution is to just buy those belt tensioner adjusters instead of fabricating them. However, I can not leave such a flawed drawing on the internet, so I have fixed the flaw in my last drawing.
In reply to VolvoHeretic :
That's by far the simplest way. But it's not the way of the one that was fabricated. Somehow the bolt doesn't move in or out, so the threading has to be on the bearing arm. The McMaster one I believe works like your drawing. I'll confirm when I buy it, but it still makes me wonder.
In reply to lnlogauge :
It must be built just like that Harbor Freight vise that sits in everybody's garage.
My wife was given an old cheap treadmill from the neighbor who was moving away. It had the goofiest contraption for tensioning and also aligning the belt. It took a long time to adjust and after awhile, it would start walking off of the rollers again. It would be interesting to see how they align a real conveyor belt.
