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Motor driven blast gate

9fingers

9fingers

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Recent changes in the workshop have put at least one blast gate out of comfortable reach and I sometimes forget to open/close them as needed too. So I had the idea to experiment with making some gates that could be electrically actuated and linked to the relevant machine.
The idea came to me on holiday where I was least able to do any more than paper sketches. The motor unit is from a central heating valve. I was able to buy a used motor head on ebay and this was ready waiting ready me when I got home.
Honeywell are one of the commonest and also the same as I have on my heating system so if the experiment fails, the spare head will be useful.

You might recognise this from your heating too.



They have a small motor and gearbox inside and slowly turn about 90 degrees when the motor is powered up and a strong spring closes the valve when the power is removed from the motor. Careful design of the motor means that it is happy to sit stalled in the open position and only consumes about 3watts from memory.

The first job was to machine the end of a shaft to fit into the gearbox.



The two flats pick up the rotating motion from the gearbox, and the small diameter pip locates in the gearbox as a reference. the near full size diameter locates in a plastic bush in the motor head body.
A bit fiddly to measure everything ( all in fractional inches down to 64ths - dontcha just love those 'merkins?)

Sample shaft fitted



As you can see the shaft is offset to one side of the motor housing and as the shaft need to be central on the blast gate, a whole lot of measurements and calculations were needed - so much easier if everything is referenced off a centre line.....

Here is the method of fixing to the pipe - standard 110mm soil pipe.



and in detail



A 55mm radius curve sits smoothly on the pipe. A couple of steel pins locate in each pair of cheeks and a jubilee clamp goes around the pipe. Making the curve on the cheeks accurately means the when the jubilee clip is tightened, the distortion on the pipe is minimal. In an ideal world I'd have machined a clamps to fit right round the pipe but this was easier and should do the job.

In between the two clamps a 1/4" thick plate is fitted, this is yet to be machined but will be the equivalent item to the top of the water valve and drilled & tapped (US threads!) to match.



In the next photo I have balanced the motor head on top of the plate to give an idea of the final external appearance.



To be continued....

Bob
 
Oooh very clever! I love watching metalwork in action. Can I come and get lessons from a you Bob, then go and spank all my cash on a lathe and mill? :)

Cheers
Mark
 
TrimTheKing":1be75zmb said:
Oooh very clever! I love watching metalwork in action. Can I come and get lessons from a you Bob, then go and spank all my cash on a lathe and mill? :)

Cheers
Mark
Click to expand...


Always happy to help Mark but metal work as a hobby can be an even more slippery steep slope than woodworking.
Start collecting stuff now and you might be getting there by retirement :lol:

I got my first lathe in 1977

Bob
 
Yes I can vouch for that apart from a lathe and a mill, the bits are smaller but a lot more expensive?

My metal working friend has just bought himself a 7 1/4 steam locomotive (train) - ouch!


Rod
 
I've been working away on this project during odd moments since I posted last.

Now the prototype is complete, it might be better to show the end result to help set the component parts in context.

So here is the completed gate.



Looking down the pipe in the closed state you can see the butterfly flap based on the design of a carburettor throttle.



and in the open position



Not the most exciting movie but here it is in action and yes I should of got the tripod out but .....
Click on the thumbnail to play


Opening could be a bit faster in an ideal world but should be acceptable.

There have been a number of issues during the build.

I found out the hard way that the dimensions of the shaft where it enters the Honeywell motor head are far more critical than I anticipated. The first attempt was deliberately a rattling good fit as I hope it would take out alignment issues. However the diameters of each section of the shaft are critical to keeping the gears in mesh. Even the little pip in the end needed to be within a couple of thou.



I had to deal with any misalignment in another way. Trying to clamp something on drain pipe is bound to move out of line with time and temperature so it is not a case of simply accurate machining.

I made my own version of a classic mechanism to deal with misaligned shafts called an Oldham coupling.
this consists of three pieces show here all aligned.



and with exaggerated misalignment



The central part is a disc with a tenon on each side. the axis of the tenons are at 90 degrees.



these tenons fit into matching grooves in the other two parts

The end of the motor shaft



and the end of the butterfly shaft



a few other shots of the Oldham coupling parts





As the coupling turns, the central portion tenons can slide in either of the grooves to take up any misalignment. You can buy these commercially bit much more fun to make and I needed a compact version to fit the available space anyway.

Finally the butterfly which was quite tricky to make as I needed to machine the shaft down to half the diameter and still hold it in the machine vice. I cheated and offset the flat by 0.2 mm and so just missed cutting into the vice jaws - I should have taken a picture but forgot until it was too late.

Here are the butterfly parts



and assembled



There are still a few issues to resolve but the prototype has served its purpose in demonstrating that it is possible to get a central heating valve to open/close a buttery fly of this size.

To get a good seal I need a jig to drill the pivot hole exactly across the diameter of the pipe and also to make a machining jig to create the elliptical shape required by the butterfly to fit the tube.

The latter will be interesting - a wedge of a few degrees to mount on the lathe and hold the butterfly at the same angle as the closed position whilst I turn the periphery of the the disc.

I'll try and remember to take some more pictures.

Thanks for reading.

Bob
 
Andyp":u24zuuq9 said:
Bob, is there an externally visible indication that the gate is either open or closed?
Click to expand...

Hi Andy,

Not at the moment but a couple of marks with a felt pen would soon fix this. However I have confidence that they will work as commanded.

Motorised gate operation will be automatic eventually. The relevant gate with be enabled when the particular machine starts up.
The extractor has already been automated when the saw or the planer comes on by measuring the supply current.
There are currently 8 gates but I only propose to automate 3 of them. 1 because I can't easily reach it now and the other two, saw and planer as they are the ones that get left shut at times.

The detail of the control is TBD. I wanted to get the gate working first.

Bob
 
9fingers":2lym4gyu said:
Motorised gate operation will be automatic eventually. The relevant gate with be enabled when the particular machine starts up.
The extractor has already been automated when the saw or the planer comes on by measuring the supply current.
Click to expand...

Very clever, I'd have more chance of working out how to do magic than I would of doing this sort of thing!

Terry.
 
Wizard9999":2ufqx524 said:
9fingers":2ufqx524 said:
Motorised gate operation will be automatic eventually. The relevant gate with be enabled when the particular machine starts up.
The extractor has already been automated when the saw or the planer comes on by measuring the supply current.
Click to expand...

Very clever, I'd have more chance of working out how to do magic than I would of doing this sort of thing!

Terry.
Click to expand...

I agree. There is always a delightful precision about Bob's work that I can only dream of.
 
Wizard9999":3scik7gv said:
9fingers":3scik7gv said:
Motorised gate operation will be automatic eventually. The relevant gate with be enabled when the particular machine starts up.
The extractor has already been automated when the saw or the planer comes on by measuring the supply current.
Click to expand...

Very clever, I'd have more chance of working out how to do magic than I would of doing this sort of thing!

Terry.
Click to expand...
How did you manage to get the name Wizard then Terry?

I start with the premise that something must be possible to do even if I don't know how - yet.
Then I have a bit of a think on what information/signal/inputs could be extracted from the device and carry on from there.
The results vary from "it's too hard/not worth the effort- no wonder no one else does it" through "Hmm! That's an interesting effect, how can I exploit that?" through "why did I not think of that before?".

A large pile of used envelopes reside by my chair for doodling ideas on before lobbing them into the bin.

Bob
 
I've been distracted by domestic DIY lately but now I'm waiting for the carpet fitter to do his stuff tomorrow so I've had some time to get back to this project.

I laminated some 18mm mdf together to make a plug 103mm diameter (the bore of 110mm soil pipe) on a base with mounting holes.

I first mounted it on a face plate to turn the plug to the same size as the pipe bore. Then I transferred it to the mill



The butteryfly flap needs to be made into an ellipse which fits inside the pipe at an angle of 5 degrees. The exact angle does not matter.
The jig also needs to be machined at 5 degrees to hold the butterfly at the correct angle to machine the outside edge into the ellipsoid shape.

The jig is mounted on a tilting angle plate set to 5 degrees



and then a fly cutter cuts the angle on the jig. Just a matter of watching the machine do the work



And after the machining is complete



Then mount the jig back onto the lathe faceplate and attach a butterfly.



and a closer view of the machined edge.



Note that an ellipse is the shape formed by cutting a section through a cylinder at an angle. so this jig cuts a perfect ellipse but using the circular motion of the lathe without having to worry about the major and minor axis dimensions that usually define and ellipse.
A circle is a special case of an ellipse where major and minor axis dimensions are the same.

The next jig will ensure that the hole drilled for the shaft is exactly across the diameter of the pipe.

Bob
 
Ingenious Bob. The valve seems to close 3 times faster than it opens would it not be possible to change it around so that the faster operation is the opening and the closing is slower by turning the damper 90 degrees?

Cheers

Bungle
 
Bungle":34ll5z5t said:
Ingenious Bob. The valve seems to close 3 times faster than it opens would it not be possible to change it around so that the faster operation is the opening and the closing is slower by turning the damper 90 degrees?

Cheers

Bungle
Click to expand...
That would be the difference between the spring and the motor. The motor only moves the vane in one direction, winding the spring up as it goes, when the power is removed the spring moves it back again.
Bob has it set up so the vane is closed by the spring, power only needed when that gate is open.
 
Bungle":2q4gi290 said:
Ingenious Bob. The valve seems to close 3 times faster than it opens would it not be possible to change it around so that the faster operation is the opening and the closing is slower by turning the damper 90 degrees?

Cheers

Bungle
Click to expand...

Unfortunately not. The motor drive is the slower of the movements and a spring return the faster of the two.
To do as you suggest would mean that the motor has to be powered to keep the valve closed and consuming power continuously.
On machines such as the saw, planer and router table where I plan to use these, there is usually a delay between switching on the machine and starting the cut so I'm hoping it will be OK.

Bob
 
The second problem I needed to solve was making the two holes for the butterfly shaft exactly acorss the diameter of the pipe. The plastic pipe tends to deform under drill pressure and additionally the drill can snatch and draw itself into the hole.

I made a laminated block of MDF - 3 layers of 18mm and machined the side true and square and mounted it up on the lathe to bore a hole through the exact centre to take the pipe.

Sorry no photo of this set up. I sneaked up on the bore diameter until the pipe was a tight sliding fit.

The block was then mounted on the mill and drilled across the diameter of the hole. Easily done as all the dimensions were known and centres could be found.





Once aligned on the mill, the pipe can be pushed in to the correct position. Drilling pressure on the pipe would tend to deform it into an oval, but the block stops this and the grip on the pipe tends to increase as I drill - just what I need.



Release the drill pressure and the pipe can be slid out.

The prototype is all working well and the jigs proven so production can start on a further three gates.

I'm in the middle of making all the parts and trying to acquire sufficient motor heads. I won another used on on ebay that arrived yesterday so just two more to find at sensible prices.

Cheers

Bob
 
I grabbed some workshop time today to start the build of three more motorised gates.

Lots of repetitive manufacture but some opportunities to save time.
eg making these part for the clamps.



Each gate uses four of these where the curved section has to be an exact fit on the circumference of the pipe.

One the holes were drilled in each piece, they were bolted down as a stack of 12 on a scrap block of aluminium.



Using a single point fly-cutter set to the radius of the pipe (55mm) I took progressive cuts of about 0.5mm at a time to start to form the curve.



After a few more cuts, the job was complete. All 12 parts cut at the same time means they must come out the same size & shape.



SWMBO is going out for the day tomorrow, :eusa-dance: so more workshop fun then with luck.

Thanks for looking

Bob
 
TrimTheKing":2pw7pvyl said:
I soooooo wish I knew how to do metalworking…. :(

Cheers
Mark
Click to expand...

I guess it is an easier material to work with than wood - none of problems associated with grain, splitting, weakness etc

Maybe partition off part of your new workshop and start to collect some metalworking toys. partitioning needed as oily things don't go well with wood and wood dust can ruin precision machines.

Bob
 
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