No vibration damper?

[tvrgeek]

Tuning up my machines. Made me wonder. Why aren't their shock absorbers in an idler in out belt drives to reduce vibration? If a gas shock, might even provide optimal tension without adjustment.

Link belts sometimes help, good segmented belts help, flat multi-rib help, but all can go through harmonics. A damper could reduce that.

 

[chris_goris]

Cost

 

[tvrgeek]

Yea, low end machines are sold by cost, not actual performance. I know the sheaves are not perfect. If I had a metal lathe, I would true them. Most drill presses violate the minimum radius for the V-belt for the low speed on the motor end. It takes a lot to go from 3600 to 400.

Curious. Several videos showing how great link belts are, only show defective belts and wrong tension. In other words, fraud. Not saying the link belts are bad, just the hack videos of non-experts.

I did find several patents on the idea of a damper. Seems sketchy as I would consider it prior art. As drill presses usually have the center idler arm, I wonder if a damper on it would even out the two belts without adding a idler and spring. Hard part is finding a damper that I can change the oil in to adjust. An old Armstrong lever off an MG might work.

My TS is harder. Ribbed belt. The problem is as it raises and lowers, it moves, so a spring provides tension. But the spring is very short so the tension varies quite a bit. A counterweight might be a better design. My old belt was bad so put on a new one. Kind of wonder if it is good as it is not as smooth as when the saw was new. Amazon belt, not a Gates.

My joiner seems pretty smooth after putting on a new cogged belt. But I could tension it fixed. It sits more than my other tools, so a link belt might be a better option. Changing the belt is a PITA. Actually, a big lever to pull the tension off would be a smart mod.

 

[junquecol]

Because the viberation is based upon a harmonic, I don't hink a gas shock would help. On my Delta Contractor's saw, link belt and tuned sheaves helped greatly. Remember that cast iron sheaves are machined. Some blades introduce a harmonic of their own. With a little experience, you can tell when a saw is running a 50 tooth combo blade. It has it's own unique sound, and doesn't matter what saw it's on

 

[chris_goris]

I also think you would find the more you use your machines the belts will not take a set and induce vibrations. I have found this to be true when my equipment was in storage after I moved before building my shop. Sometimes the belts just need to warm up a bit.

 

[Oka]

I read an engineering report for HVAC units that are belt-driven systems. The author did a critical analysis and comprehensive testing on several types of belts and sheaves.

Short version- with sheaves, make sure they are solid steel machined type. The cheaper ones are lighter and tolerances are all over the place.
With belts, the ribbed belts if the pulleys are configured that way or the cog belts are best for experiencing the least amount of vibration and maximum amount of torque transfer.

 

[tvrgeek]

Because the viberation is based upon a harmonic, I don't think a gas shock would help. On my Delta Contractor's saw, link belt and tuned sheaves helped greatly. Remember that cast iron sheaves are machined. Some blades introduce a harmonic of their own. With a little experience, you can tell when a saw is running a 50 tooth combo blade. It has it's own unique sound, and doesn't matter what saw it's on

Actually where a hydraulic damper is beneficial. Remember, their function is to lower the Q. The function of gas in a gas shock is to reduce the foaming as the fluid passes the valves so maintaining the value. But as they by nature provide a little spring force, that might be useful for self adjusting.

We don't always have the option of nice steel machined sheaves. I had a heck of a time getting one close enough for my drill press. ( Original Delta one was bored off center!) Spacing was slightly different from industry norms. Not all cast are machined. Take a look at some HF tools. For that matter, the alloy one I got for my DP was die-cast and only cleaned up on the seams. It was not turned true.

Yes, cogged belts if the radius is any where near the lower end. Lower durometer rubber if you can get it. If you can run a multi-groove flat belt, even better but as they are wider, not common on 12 speed drill presses. My TS does run one. I am wondering if the brand was a poor choice.

All belts will vibrate, The point is how to reduce it after the proper design is already implemented.
Yes, all belts wil take a set especially with small diameter sheaves. I have sketched a little lever to release the motor on my joiner much as I release the tension on the BS band. If I can figure it out, it may even be possible for the damper to release the tension on the DP. Fuzzy in my mind, but should be possible. Key is a longer rear belt with an idler/damper.

 

[Oka]

With any belt driven motor system, too tight or too loose will cause increase of vibration too. The only real modification I see would be, to add harmonic dampers. Put them in 8 locations where the top meets the base equally spaced. Then, any vibration would be dampened. Any other add would get tricky and likely to make things worse. Trying to modify the motor to arbor part would require a lot of re-engineering with small benefit.

 

[tvrgeek]

That is another design fault of a lot of machines. Inconsistent tension. On a typical drill, you set it by guess every speed change. On my saw, it varies with depth of cut.

Diving into the weeds. ( That's what us techies do)

Only my joiner and band saw are a fixed distance, so an adjustment remains. ( and pretty smooth) . Joiner came with an A36 belt, which has a minimum spec of 4 inch pulley. I put on an AX37 with a spec of 2.4 inches. This is a common problem on woodworking tools. Pulleys are too small for the belt. Ridgid manual says belt tension is "1 inch deflection" but that does not give the force necessary. Even if I had a gauge. Tension depends on RPM, distance between sheaves and diameter of sheaves. FWIW, link-belts have the same spec as AX series, so no magic advantage there.

I found this from Continental, courtesy of Granger: https://www.grainger.com/ec/pdf/458T89_1.pdf
And it led me to : Continental Industry - Service

First run, guessing a few values, it says I should apply about .6 Lbs for 1/4 inch deflection. I'll go get the missing specs after my coffee. What is confusing is the three gauges they sell range 30 to 150, 100 to 300 and 300 to 700 Lbs so this must be reading tension which is another calculation.

As the drill has a lever for applying tension, I might experiment for a range of speeds, manually adjust the tension while running and see if the vibration changes.

 

[chris_goris]

What TS do you have? Something sounds very wrong with the "tension varies with depth of cut". Also, not to knock your machines, but it sounds like they are lower end pieces to start with, hence cost about quality of all components. Also, larger, more expensive woodworking equipment is much less affected by any belt vibration do to the mass (much more cast iron and steel to deaden it). For instance I recently purchased a used Bridgewood 15" belt sander, this is an industrial quality belt sander . It has 2 V belts driven from a 5 HP motor in the bottom of the cabinet, these belts are probably 40" center to center on 3" pulleys. They appear to be very loose but are actually "tight" , I can move them side to side in the middle of the 40" probably 2". When the machine runs, they are flopping all over , yet, I feel zero vibrations in the machine.

 

[tvrgeek]

Ridgid contractor saw. Virtually all contractor saws use either gravity or a spring. As height changes, the spring takes up the slack, but it is a very short spring so the tension changes quite a bit. Gravity is probably a bit more consistent.

My tools are not professional production level. No money, no room, no excuse. For sure, as I have suggested to as many first time anything buyers, bigger and heavier is better. This is why I am killing myself deciding between a Harvey, Powermatic, and PCS 3 HP cabinet saw as an upgrade. I decided against the Bailey and Grizzly as they are dovetail trunnions. My reasoning is they are assisted by a gas spring which only last a few years and I have no idea if they are generic. I am slightly scared on the PCS as it has so many unique parts like the very short secondary belt that again, will it be available 20 years hence?

DP is the ubiquitous Delta 17 from years passed. I made the mistake of thinking it was a quality machine but even 20 years ago, seems the Taiwan factories started shipping junk. I would have bought the Palmgren but for the T-slot table. Never had one and my go to clamps and jigs are all for through slots.

Joiner (reasonably smooth) is again, the ubiquitous Emerson/Craftsman/Ridgid/ you name it 6 1/8 inch. I am happy with it. ( see below)

BS is my new Harvey C-14. Smooth as can be. Love it. Drive belt is a very short multi-rib. Big massive iron wheels.

Planer is my modified Delta lunchbox. It will probably be replaced with the Delta 735 like everyone else, even if they lie like a dog on the power requirements.

Did some testing on my DP. Running @ 450, played with the tension. It is very clear when the minimum tension comes in. I don't have a force gauge, but my "moderate" uncalibrated thumb says it is about 1/2 inch on the rear belt. Just a tad loser than I might typically have set. Tighter did not change the vibrations. I have not tested at higher RPM. I rarely go above 1200. I would like to go slower, but the smallest motor sheave is way below belt spec and does not have enough wrap, so I get slippage when spinning a big circle cutter that slow. The chart says I should be running 3000 for small bits in almost everything, but all that does is burn its way through. When I am cutting metal, I expect to produce curls or chips, not dust.

If I want smoother drill, I have to buy one. Tolerances in the sheaves are just not that good. I found the motor mount to be way off skew but with some tweaking, it is now in a parallel plane. Good enough for woodworking. If I get more serious in metal fab, then I guess a Smithy would be needed.

Belts should be just tight enough to not be flopping. I have been reading as much as I can find from belt manufactures. One thing you maybe can do with 2 belts is if the sheave is "standard" go to a single bonded belt. Basically the same two belts but joined. Much stiffer laterally.

So, I have two choices for my joiner. I can either put on a link belt, or put the motor on a hinge with an eccentric on a lever to release the tension between uses. I only use it every few months, so the likelihood of the belt to take a set is greater. The motor is quite a way from the cutter. I think a big block and a shorter belt would be even smoother.

Observation: Y-tubes showing vibration and fixes only show the the machines idling, not cutting. Different blades/cutter heads, etc. may set up different harmonics. This is why I was thinking about a damper to lower the Q.

Back to installing my new DC ductwork. Last pieces came last night.