Speed Reducer Quick-Release?

[Pintodeluxe]

I have a simple speed reducer setup on a Consew 206rb.  I like the control and power of the speed reducer, but it's sometimes a hassle to release the belt to tip the head back.  Has anyone seen a quick release to de-tension the belt without using a wrench?  If there's no commercial solution, I have two ideas...

1.  Star knob to replace the bolt that tensions the belt on the smallest pulley.  That would allow me to quickly release the belt tension so I could slip off the belt and tip the machine back.  However, I'd have to get the belt tension right each time I adjust the knob.

2.  Toggle clamp (Push Style) bolted to the sliding portion of the speed reducer frame.  This should allow me to quickly release the belt tension, and lock in a consistent tension setting each time.  When tightening the toggle clamp to start sewing again, the tip of the clamp would exert light force to the underside of the table.  This is pretty hard to picture, but I'll post a picture of the installed clamp if it works.    

 

[garypl]

I use a speed reducer with a 206RB and I simply swing the head back - the belt goes loose, then when I put the head back the belt tightens up.  No problems with belt falling off.

Gary

[Uwe]

You can move the speed reducer pulley toward the back. There's a bit of science/geometry to installing motors and speed reducers. Tilting back of the machine is part of it. When installed just right the tilting works like it does without the speed reducer.

Essentially, when you draw an imaginary line through the hand wheel and the hinge pivot, the center of the connecting pulley (speed reducer or motor) needs to be slightly towards the back of that line. Otherwise you have to overcome increased tension at first when tilting the machine back. 

There's nothing you can do about the position of the hand wheel and hinge pivot, so the only thing you can adjust is the position of the pulley.

Here's a quick diagram that hopefully illustrates the concept. Green pulley (or motor) position is good, red position is trouble when tilting the machine back. The graphic exaggerates a little. Pulley on that line or slightly behind is fine. 

In the red pulley position the distance between hand wheel and pulley (and thus belt tension) increases at first, then decreases as you tilt the machine back. In the green position, the distance between hand wheel and pulley only decreases (reducing belt tension) as you tilt the machine back.  

 

Edited August 3, 2018 by Uwe

[DonInReno]

Uwe did a great job describing where to move the reducer.  

Along similar lines I’m using multiple machines on one table and need a quick way to get a properly adjusted belt.  The dimensions of each machine and their hand wheels vary all over the place so each machine has its own belt and I’m looking to add a simple tensioner pulley that’s spring loaded like the one in this picture.

[dikman]

Don, I tried that with one of my tables where I swapped machines around but found it wasn't very successful. It looked like it should work but I couldn't get rid of "belt slap" so I gave up on the idea. I suspect that it was caused by having a very small pulley on the motor.

[Pintodeluxe]

Great info here.  It sounds like someone installed the speed reducer in the wrong spot, or maybe had to work around obstacles.  Uwe, thank you for the detailed description of how to mount the speed reducer properly.  

If I can't relocate the speed reducer, I'll try my quick release idea.  I'll still have to slip the belt off, but at least it will be loose.

Thanks for the replies!

[SARK9]

The main limiting factor I encountered when mounting a speed reducer/servo combo was the location of the stock motor's bolt hole pattern in a "regular" 21x48 industrial table. If you reused those holes for mounting your servo motor, it was nearly impossible to place the reducer pulley's mount far enough back to keep the large pulley on the reducer from actually interfering with the motor pulley, since to allow your machine head to tip back normally, the reducer pulley must be located in a position which places the centerline of its axle BEHIND the centerline of your machine's hinge pins. You actually need the pulley which has the belt driving your handwheel pulley to end up in about the same fore-and-aft location as the original stock clutch motor's pulley, in a nutshell. This lets you have the tilt feature and requires no modification of the table's belt slot for extra clearance.

When using a "pedestal" mounted speed reducer of the type shown, the easiest solution was to make a motor mounting offset plate which attached to the 3 existing table bolt holes, and had a set of 3 tapped holes by which to attach your servo motor to the table in a new location. No one likes drilling more large holes in their table!

 

-DC

[CowboyBob]

Edited August 4, 2018 by CowboyBob

[brmax]

Sark9: That is an extremely nice reducer you have machined and setup. 

Also just saying a very professional write up and especially with regards to the standard bolt hole mountings. 

This plate you made for an adaptable mounting of the motor or any bolt pattern of the same is great work, I have found this to be a use in my own tables. 

In my plywood adapter, needed only for a reducer install I needed to initially get below some 2” angle support bracing I made for my tables long ago. The adapter I found to be a benefit in both directions. Thanks for sharing your build. 

 

Good day

Floyd

 

[Garyspruill]

Cowboybob,

That is a great looking reducer. (top image)

You could get that slowed down to around 30 stitches a minute with no torque loss at all. Great job!

I'm calling you when I need one.

Gary

[Ken Nelson]

Cowboy Bob,

Are you selling that speed reducer and if so, How much?  Thanks

[CowboyBob]

Yes,we are it sells for $190.00+ UPS. It give a 3-1 reduction same as the other type.

[BattleAx]

Edited August 4, 2018 by BattleAx

[BattleAx]

2 minutes ago, BattleAx said:

Had some scrap angle a couple of pulleys  ordered bearings and a shaft from eBay works very nice.

[DonInReno]

On 8/3/2018 at 9:03 PM, dikman said:

It looked like it should work but I couldn't get rid of "belt slap"

 Yes that odd “pulsing” tendency of the belt does make a spring loaded tensioner harder than it looks to overcome.  I’ve seen a few that incorporate a small shock absorber piston so the tensioner can move, but can’t quickly cycle in and out with the variations in the belt/pulley.  With the proliferation of soft closing hinges and drawer slides in cabinets, there are a few parts that seem ideally suited, but I have no idea if the pistons have enough resistance and travel.  There are small industrial soft close cylinders in varying amounts of resistance, but they are too $$$.  Hell, half the new toilet seats are soft closing so something cheap should work! Lol

Another design uses a one-way bearing and friction clutch like the drag on a fishing reel so it cinches down easily but requires much more force to loosen.  Unless it’s incorporated into an automotive tensioner that can be modified for less spring force that seems too complicated to cobble together.

The pivot bolt could always be tightened so the spring adds the tension and the position is simply locked in place.  

In the end maybe it’s no more complicated to add an easy method of moving the motor.  Moving the super smooth feed handwheel of a mill or lathe makes me think of an easy to reach handwheel moving the tensioner...hmm...

I also wondered if pulley size made a difference in belt slap, but when I added a larger drive pulley it actually became worse - in this case the paint on the pulley had more grip so the belt would noticeably ride up where the belt was slightly thicker.  

 

Edited August 5, 2018 by DonInReno

[dikman]

I think for this to work the tensioner needs to have a fixed adjustment, for instance a sliding tensioner fitted with a screw adjuster to keep constant tension on the belt. Perhaps not as convenient as a spring loaded one but it would still allow slackening off the belt without moving the reducer or motor assembly.

[brmax]

I believe if you wanted to fabricate a very square and supportive bracket. You could use one of the many many small gas cylinders made for lifting and etc. 

The ticket would be finding one at a price your happy with, they are sure out their, good luck with it.

 

Good day

Floyd

[Pintodeluxe]

BattleAx, that is an impressive looking improvised build.  Takes me back to my Erector Set days as a kid!  Nice work.  

[CowboyBob]

1 hour ago, Pintodeluxe said:

BattleAx, that is an impressive looking improvised build.  Takes me back to my Erector Set days as a kid!  Nice work.  

Yes,very well built & look like it'll do the job.

[Pintodeluxe]

I didn't think I could move the speed reducer far enough backwards to alleviate the problem, so I installed a toggle clamp quick release.  Cowboy Bob's solution looks best, but this works in a pinch.  Now at least I can release belt tension to tip the machine back for maintenance.  When I lock the quick release, the belt tension is set automatically.  

  I did need to drill a slot in the toggle clamp, but no modifications to the speed reducer are required.  A low profile furniture connector bolt attaches the toggle clamp to the speed reducer.  The bolt that comes with the speed reducer is re-used and threaded finger tight with locktite.  

[Pintodeluxe]

[Pintodeluxe]

[Uwe]

That locking lever is actually a very cool solution. Thanks for posting the details!

[dikman]

Nice. I like it. I think I'd re-route that cable, though, just in case. It should be ok, but.......

[DonInReno]

Very cool!