Author Topic: ENGINE SPEED GOVERNORS  (Read 3616 times)

Offline Brian Rupnow

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Re: ENGINE SPEED GOVERNORS
« Reply #45 on: May 09, 2019, 06:12:14 PM »
George--we may be on the same page. The way I see this is that when the flyweights are close to the center spindle, in a static no load position, the throttle is held wide open. As soon as the engine starts, the open throttle spins the engine and governor up to a speed where the flyweights come out under centrifugal force, and force the lever back to whatever rpm you have the governor set for. The engine is driving something that imposes a varying load on the engine. As the load increases and makes the engine slow down, the governor senses this loss of speed and consequently moves the arm to open the throttle a bit more to increase the engine speed back to whatever speed its was at before the load was imposed. So--The natural movement of the governor is to increase the throttle opening as it senses less speed at the engine. When it senses zero movement of the engine, the governor reverts to it's "at rest" position with the throttle held wide open. We have a finger adjusted "knob" which tightens or loosens the counter spring, which works against the flyweight springs on the governor. By increasing or decreasing the tension in the counter spring, we are able to adjust the rpm at which the governor responds.  If we want to start the engine with the throttle in the closed or "idle" position, we have to find a way of removing any effect the governor is exerting on the throttle. My idea is to install a positive "stop" at the throttle so that it can not advance to a higher rpm. The governor now still works the same as ever and tries to initially move the throttle to a wide open position, but it can't, because of the positive stop I have on the throttle plate. So---All that happens is that the spring in the linkage between the governor and the throttle is compressed but there is no resultant movement at the throttle end of the linkage. When I want the governor to work, I remove the positive stop and everything reverts to "governed rpm".

Offline gbritnell

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Re: ENGINE SPEED GOVERNORS
« Reply #46 on: May 09, 2019, 09:01:01 PM »
Hi Brian,
On a governor for a small engine the engine starts with a closed throttle. Otherwise it won't start. The throttle lever on the handlebar is in the idle position and the throttle plate is closed, or almost closed. Idle setting) The engine is started and the throttle lever is moved to the operating speed. The cable doesn't open the throttle but pulls on a spring hooked to the governor lever. The governor lever has a rod that goes to the throttle plate. There can't be any solid mechanical connection between the throttle lever and the throttle plate otherwise the governor couldn't control it.
So when the engine starts and is throttled up it pulls on the spring hooked to the governor lever. The governor lever also has a load or return spring, whatever you choose to call it. This spring controls the rate of movement of the governor weights and therefore the governor shaft. Once the engine is started the handlebar lever is moved to increase the engine speed. This movement pulls on a cable which pulls on a spring which pulls on the governor lever thus overriding the control of the governor and speeding the engine up. At this point the linkage spring and the governor spring are basically in balance for the desired engine speed. As the engine is put under load and slows down. the governor starts to close down because of the reduced speed allowing the tension of the cable spring to override the governor and speed the engine up.
You can start a lawnmower engine and set the throttle. Now you can reach down to the lever hooked to the governor shaft and pull on it which will increase the engine speed but you will feel the resistance increase from the governor trying to control the engine.
gbritnell

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Offline Brian Rupnow

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Re: ENGINE SPEED GOVERNORS
« Reply #47 on: May 09, 2019, 09:53:32 PM »
Okay George--I will have to think on this. Thank you for your help and guidance.---Brian

Offline gbritnell

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Re: ENGINE SPEED GOVERNORS
« Reply #48 on: May 09, 2019, 11:08:30 PM »
Hi Brian,
Here's quick sketch of the typical governor linkage.
When the engine is at idle the cable link hasn't loaded the spring between it and the governor link. The throttle plate is closed. Engine can be started.
When the engine starts at slow speed the governor is keeping the throttle closed.
When the throttle lever is opened it moves the cable link and therefore pulls on the spring hooked to the governor link. This opens the throttle plate, increasing the engine speed.
If the engine were to go too fast the governor would override the spring and close down the throttle to a speed controlled by the tension of the spring and the centrifugal force of the governor weights.
As the engine slows down the governor link moves to the right being pulled by the spring and increases the engine speed.
You can't just have the throttle plate hooked to the governor, well you can but you have no way of increasing the speed because as the governor spins it wants to keep the throttle closed. You need another adjustment (spring) to load the governor arm.
Most newer mowers have no manual throttle control. You start them and they run to a preset speed. When the engine needs more power (slows down) the govenor opens the throttle more to maintain a set RPM. The governor never slows them down past the pre adjusted running speed.
gbritnell
« Last Edit: May 09, 2019, 11:13:12 PM by gbritnell »
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Offline Brian Rupnow

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Re: ENGINE SPEED GOVERNORS
« Reply #49 on: May 09, 2019, 11:15:21 PM »
This is going to get very interesting. I ordered a 3/8" Lovejoy coupling today, and I will use it to connect the camshaft of the horizontal sideshaft engine I just finished to the governor, all on a common base. The engine will eventually drive something with a varying load to see how the governor responds.

Offline Brian Rupnow

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Re: ENGINE SPEED GOVERNORS
« Reply #50 on: May 09, 2019, 11:26:45 PM »
This is the sketch George Britnell sent me re. governors. Thank you George.

Offline Ian S C

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Re: ENGINE SPEED GOVERNORS
« Reply #51 on: May 10, 2019, 03:22:21 AM »
A problem was found with early mill engines that if the drive belt to the governor broke the engine went to full throttle, sometimes with devistating effect, burst flywheel that sort of thing, so a mod was made , a jocky wheel ran on the belt, and when the belt broke the jocky wheel closed the throttle. This was steam, but the same with IC engines.
Ian S C

Offline gbritnell

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Re: ENGINE SPEED GOVERNORS
« Reply #52 on: May 10, 2019, 11:58:33 AM »
Actually the jockey wheel was part of the steam governor. The governor valve was loaded with a coil spring and ratchet mechanism. When the belt broke the arm that the jockey wheel rode on would fall with gravity and trip the ratchet mechanism causing the governor valve to close. The governors on gas engines are mechanically driven so they don't have the weak link (the belt) like steam engines.
gbritnell
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Offline Ian S C

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Re: ENGINE SPEED GOVERNORS
« Reply #53 on: May 10, 2019, 01:43:35 PM »
The governors on 'most' gas engines are mechanically coupled, some such as the NZ built Anderson stationary engine, an enclosed vertical either single or twin cylinder motor has the governor driven from a pulley on the crankshaft, originally by a round leather belt similar to the old treadle sewing machine, although our motor has a bit of rope at the moment. For about 60 years the motor was used by the local council driving a concrete mixer until about 20 years ago when we obtained it in rough but going condition.
Ian S C

Offline Brian Rupnow

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Re: ENGINE SPEED GOVERNORS
« Reply #54 on: May 10, 2019, 05:13:05 PM »

Offline gbritnell

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Re: ENGINE SPEED GOVERNORS
« Reply #55 on: May 10, 2019, 05:58:26 PM »
This was a model of a Pickering steam engine governor in 2 inch scale that I made. It shows the latch and release mechanism to shut the valve off should the belt break.
gbritnell
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Offline john mills

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Re: ENGINE SPEED GOVERNORS
« Reply #56 on: May 11, 2019, 02:07:16 AM »
the petrol engines I have ronaldson tippett   and villiers engines all the governors hold the throttle fully open
when the engine is stopped on starting the throttle closes to the set speed if it has unadjustable speed then
it controls the speed to what ever the adjustment is set and can be altered as required.

Offline gbritnell

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Re: ENGINE SPEED GOVERNORS
« Reply #57 on: May 11, 2019, 10:15:04 AM »
My mower is also like that but it has a primer bulb to basically flood the carb for starting. I have never been able to start my model engines with the carb wide open. Maybe a finger over the carb while cranking to choke it might help.
gbritnell
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Online Captain Jerry

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Re: ENGINE SPEED GOVERNORS
« Reply #58 on: May 11, 2019, 05:37:03 PM »
Governor accidents were occurring well into the 1970's.  Foundries commonly used an air powered grinder to clean up cast iron municipal  castings, manhole covers, etc.  The tool was a 4-6 horsepower air motor directly driving a a 6" abrasive cup wheel.  They were supplied with guards but the guards were seldom used.  The shaft speed was controlled by a governor and the operator usually held the throttle wide open, letting the governor provide full power when he hogged down on a rough casting.  Ingersol-Rand an Chicago Pnuematic were major suppliers.  Under such heavy use, the governor springs were known to fail, with catastrophic results.  The shaft speed could accelerate from 3000RPM to well over the max safe speed of the abrasive wheel before the operator could release the throttle lever and the wheel would explode. A smaller company, Master Air Tools introduced a grinder with a fail safe governor and made a great impact on the industry.  I don't have any details of the  governor design but it saved a lot of legs.


Jerry
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Offline Brian Rupnow

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Re: ENGINE SPEED GOVERNORS
« Reply #59 on: May 11, 2019, 10:13:13 PM »
Hi Captain Jerry--Glad to see you are back in the saddle again. Haven't heard much from you in quite a few years.---Brian