High-force Push Solenoid

Hi, I am having some trouble looking for a push solenoid that I need for a project.
I am looking for a push solenoid capable of pushing at about 5 kg.
Furthermore, I want to be able to vary this force. I am using this to push a fully weighted piano key to create different loudnesses, so the dimensions of the solenoid need to be relatively small. Does anyone know an appropriate device for this application, or shall I be forced to make my own?
Thanks for your help.
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mtowns wrote:

Hi, Try a place that supplies pinball repair parts. They probably won't be marked for the force availible, but there are many varieties to mess with. It has been a long time since I searched through solenoid vendors catalogs, but as I recall, 5 KG is a lot of force from a solenoid.
Another thing to think about is that powerful solenoids will heat up quickly if you hold them energized. Some of the pinball solenoids have a separate holding coil that will not provide as much force, but it will not heat up as fast while keeping the plunger pulled in. When the solenoid heats up, it's DC resistance increases, so it will have less force on subsequent operations until it cools.
The force is proportional to the current in the coil. You can control the force (and correct for thermal issues mentioned earlier) with a current source drive instead of a voltage source drive circuit.
Good Luck, Bob
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mtowns wrote:

5Kg is a hell of a lot of power from a solenoid - you will be drawing several amps at 24v for that sortof thing. I suggest making your own using an electric door lock magnet (energize to lock) with a plate of iron/steel and a through-hole shaft.
Side view: Sheet Iron / =======||====== _____ || _____ |_____||||_____|-Magnet || ||- through-hole shaft.
When the magnet energizes it pulls the plate of iron down and pushes out the shaft.
You may need to drill the hole yourself for the shaft and a return spring would probably need to be slid between the magnet and the shaft. Some of these magnets run off 24v and so could be PWM though a lot run from mains.
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I discovered that solenoids used in things like washing machines and the like behave very well with a variable speed resistor much like what you use in dimming lights in the living room after sipping that glass of wine with your most significant other and.....
But these are pull mechanisms, so you need to create a fulcrum and lever device and have them work upside-down on your piano. So a linkage is required. But the force control with the light-switch control is quite keen.
I have a breadboard of the device I'll be happy to photograph and send to you you'd like to see it.
Wayne
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mtowns wrote:

I have made solenoids in the past from automotive starter solenoid coils.
These flow 20A @ 12V and push ~ 20kg.
Haven't seen a commercial one more than 2kg or so from mmemuri?...momery?...ummm...memmeri...yer, thassit!
Stroke may be a problem too...you will need 10 odd mm to operate a piano key no?
If you make your own solenoids (88 of them?) they can be placed closer together by using long & short actuation rods... _-_-_-_-
And use steel cases to provide a magnetic circuit...the end cap is important in hold applications, but if you are going for a linear force adjustment via current control it may not be needed
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