Brain turned off!!

[teamcowboyup]

So I'm trying to figure out how to build a spring tension for a homemade mill or even just a plain bolt tension system but my brain turned off.  If anyone has any input or good pics please share so my brain might work lol.

[teamcowboyup]

Also I have springs already. 4x1.5 at 1250lbs per inch free spring length (3inch free spring). 

[Crusarius]

Are you trying to tension the blade? or lifting? or guide around the uprights?

The other thread I thought you meant lift assist springs.

[teamcowboyup]

Spring tension refers to blade tension. 

[york]

youtube then Cooks-they may have a video on what your looking for.....

Will look for pic. of my setup ,i would use Acme rod,not all thread or ready rod-mine is TH and Cooks is about the same.....

[Kbeitz]

I'm thinking that springs will give a much bigger bang when the blade brakes.
This made me go without one on my build.

[SineWave]

I'm thinking that springs will give a much bigger bang when the blade brakes.
This made me go without one on my build.

Me too. Also, springs weaken and blades stretch, and you still need a way to measure tension. Another reason I'm going with the hydraulic tensioner and pressure gauge (Linn Lumber head)...

[ladylake]

No way I'd be without a spring as there is some give if the v belts aren't perfect and you don't lose tension soon as the blade heats up a little .  Steve

[Kbeitz]

No way I'd be without a spring as there is some give if the v belts aren't perfect and you don't lose tension soon as the blade heats up a little .  Steve

You might be right but I don't use Y-belts or tires.

[york]

Only one method better then, using a spring, use air,think about it.....

[Den-Den]

Springs make sense to me if you are using steel wheels, not so much if using tires.
Are the springs you have, made to use in tension or compression?  Adding a short & strong compression spring to a threaded rod or hydraulic cylinder should be easy.  Mounting two or more in parallel to get a high enough spring rate would complicate things a little.  Tension springs could be used with a cable and pulley but that adds more parts that could fail in dangerous ways.

I tend to agree with Kbeitz that a spring could add to the drama of breaking a blade but don't think it would add enough to matter. 

[Kbeitz]

Only one method better then, using a spring, use air,think about it.....

There is no way I would use air. If the blade would brake things would really go flying.
I think of it like testing a boiler. Doing a tank pressure test you use water. If the tank breaks
nothing happens. Using steam or air and it breaks things keep moving.

[Den-Den]

Only one method better then, using a spring, use air,think about it.....

There is no way I would use air. If the blade would brake things would really go flying.
I think of it like testing a boiler. Doing a tank pressure test you use water. If the tank breaks
nothing happens. Using steam or air and it breaks things keep moving.

If a blade breaks, it will fly apart from its own tension whether there is a spring or not.  A spring would push the wheel outward if the blade breaks.  The wheel has a very high inertia compared to the blade so I don't see how the wheel moving could add any speed to the blade.  I would want a strong stop block so that the wheel could not move far.  Careful planning could make things safe with a spring or with air.  Lack of planning when building machines can kill.

[Magicman]

I believe that the LT70 uses an air bladder.  For a spring I would consider an engine valve spring(s).

[Percy]

I believe that the LT70 uses an air bladder.  For a spring I would consider an engine valve spring(s).

You are correct sir. When the blade is at the correct tension, there is a stop bolt about a quarter inch away from the business side of the air bladder. When a blade breaks, there is a bang but it is a non event.

[paul case]

Thar is the same as with the spring tension on the EZ boardwalk 40 I had.



 

PC

[Kbeitz]

For the people that want to use springs I was told that die springs work best.
They are color coded for strength. I was told you want the blue ones.
I have been cutting with my mill for around 2 years now and I don't see the need
for springs. Maybe one time a spring might have helped me when pine sawdust
built up on my wheels before I seen it and broke one of my blades.
Good luck with what ever you use.

[Magicman]

Kb,  Sawdust buildup is a way of life.  I doubt that sawdust buildup would cause enough additional blade tension to break a blade.  I suspect that your blade was about to go anyway. 

[Larry]

The big bang of a spring can be avoided.  In my fabricated system after the blade is tensioned and the spring compressed the nut is spun up against the frame bulkhead of the mill.  If a band breaks, nothing happens.  (Patent Pending) :D :D



After I made the above I thought of a method to automatically tighten the nut....but I didn't do it and forgot how :-[.

An exploded view of my spring assembly.  What appears to be washers are actually three different types of thrust washers.  The white one is plastic, than bronze, and a needle bearing.  I tried all three with the clear winner being the needle bearing.  I was afraid the needle bearing would rust but no problems.  They are available from McMaster Carr for a couple of bucks.



Zero problems with my assembly after two extremely hard easy years of field testing.

BTW the reason we don't want a big bang is because when the wheel assembly slams into the bulkhead that can't be good on the bearings.  Also it kills the TK gauges that measure tension.

[Grizzly]

BTW the reason we don't want a big bang is because when the wheel assembly slams into the bulkhead that can't be good on the bearings.  Also it kills the TK gauges that measure tension.

Agreed. That's why, yep.........but you left out the very stretched and rattled nerves I have after it happens!   :D

[JRWoodchuck]

I just used acme threaded rod for mine tightened with a torque wrench.



 

[Kbeitz]

I used hardened all-thread with long nuts.



 

[ladylake]

I'd put a die spring between that nut and the metal. it will be easier on your blade and keep the tension more consistent.  Also convert it to acme thread which tensions faster and easier.  Steve

[ladylake]

The big bang of a spring can be avoided.  In my fabricated system after the blade is tensioned and the spring compressed the nut is spun up against the frame bulkhead of the mill.  If a band breaks, nothing happens.  (Patent Pending) :D :D



After I made the above I thought of a method to automatically tighten the nut....but I didn't do it and forgot how :-[.

An exploded view of my spring assembly.  What appears to be washers are actually three different types of thrust washers.  The white one is plastic, than bronze, and a needle bearing.  I tried all three with the clear winner being the needle bearing.  I was afraid the needle bearing would rust but no problems.  They are available from McMaster Carr for a couple of bucks.



Zero problems with my assembly after two extremely hard easy years of field testing.

BTW the reason we don't want a big bang is because when the wheel assembly slams into the bulkhead that can't be good on the bearings.  Also it kills the TK gauges that measure tension.

Nice set up Larry, I'm thinking if I slide a piece of plastic hose or maybe heater hose over the rod between the threaded block and the frame that would limit the travel  when a blade breaks also if it would hold up  .  Also convert your tensioner to acme threads, it will take 5 1/2 half turns to tension up instead of 9 and turn easier, I just that on my B20 and should have done it 10 years ago  . Steve

[Larry]

Also convert your tensioner to acme threads, it will take 5 1/2 half turns to tension up instead of 9 and turn easier, I just that on my B20 and should have done it 10 years ago  . Steve

Yes, I should have used acme.  If I ever have a problem I will go that route.