Need mathematical help with new mechanism

[frank brownParticipant @frankbrown22225]

So I have a cottage in a wild and windy place with an en-suite. I have built a heat recovery system for it which seems to work. My problem is that for 23.5 hours of the day, heat is escaping from it. So it is always cold to start off with and so I thought I need a way of sealing the air ducts when not in use.

I have built a prototype which is a geared down induction motor (as used in washing machine timers etc.) driving a flap that moves through 90* to open or seal the 4" air duct.

The motor which only starts and stop and runs in one direction is 46.6mm from the hinge pin of the flap. At a distance of 17.02mm from the centre of the motor shaft is a bearing onto a connecting rod of 40mm centres. The connecting rod then connects on to a disc ,24.4mm from the centre of the flaps hinge.

I have mounted microswitches on the other side of the flap so the motor only stops when the flap is open or closed. The whole thing works beautifully, with a change over light switch the flap opens an closes.

There is no slop to speak of in the con rod bearings, but I am worried that when I proceed to invest in stainless steel shafts etc, that the whole thing will jam up. So I thought I would do maths on the various bits and pieces to prove to myself it can work. But I can't seem to even get started.

So has anyone seen a con rod mechanism working on unequal swing arms and its mathematical proof?

Frank

[frank brownParticipant @frankbrown22225]

Any good with sines and cosines?

[Brian OldfordParticipant @brianoldford70365]

Could you produce a sketch of what you have. A picture says a thousand words.

[JasonBModerator @jasonb]

If I understand your figures correctly you will only get about 84deg movement of the flap

[JasonBModerator @jasonb]

No you are a lot closer to 90deg than I thought, so stick with what you have as it won't matter if the flap moves a fraction more or less than 90deg from closed

[frank brownParticipant @frankbrown22225]

Thats brilliant Jason, Did you have just do it graphically?

Frank

[MWParticipant @mw27036]

What is this marvelous program that produces these intricate pictures, Jason?

Michael W

[JasonBModerator @jasonb]

Alibre, Geometric design, Cubify Design – all the same basic programme that has had a few name changes in the last few years.

Thats really just the rough geometry using the dimensions given and the fact they move radially. Could flesh it out into discs and conrods but was too busy watching Le Tour to bother.

[JasonBModerator @jasonb]

Comes out at about 90.6deg flap movement and looks like it will work

 

Bit rough and ready but principal is right, small disc is the one on the motor, large on the flap valve

Edited By JasonB on 10/07/2016 21:01:17

[Tim StevensParticipant @timstevens64731]

Jason says '… principal is right …'

Not quite, Jason. Principle is right, Principal is the bloke at the top of the school stairs who is paid not to teach.

Cheers, Tim

[Michael GilliganParticipant @michaelgilligan61133]

Nice animation, Jason

A picture is worth a thousand words, and an animation even more.

MichaelG.

Edited By Michael Gilligan on 11/07/2016 15:38:03

[JasonBModerator @jasonb]

Posted by Tim Stevens on 11/07/2016 14:54:16:

Jason says '… principal is right …'

Not quite, Jason. Principle is right, Principal is the bloke at the top of the school stairs who is paid not to teach.

Cheers, Tim

That's why I was always better at maths and geometry than English

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