Eclipse Inertia Starter

General information about Wing42's Lockheed Vega.
Jarek
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Eclipse Inertia Starter

Post by Jarek » 06 Jul 2018, 01:20

Here are some details about Direct Cranking Starter Motors manufactured by Eclipse Aviation (Bendix subsidiary). This picture I believe is from 1938. In principle, the construction did not change much till present times. Starter switch is connected to the solenoid, which engages high-amperage circuit. So if fused, it should not be much sensitive to the battery voltage.
eclipsey.png
eclipsey.png (23.81 KiB) Viewed 422 times
But these direct starters arrived in late '30. Earlier, in late '20 and early '30, electric Inertia starters were used (probably due to lack of sufficient amperage capacities in early batteries). An example of such flywheel-assisted starts could be found in the movies that could be found in the Vintage Videos section. This will affect engine startup procedure and characteristic rotating flywheel sound. We have mention about "No. 6 Eclipse inertia starter" in the Winnie Mae book.

A quote from British "Flight" magazine, March 7, 1929:

"An easy method of starting large internal-combustion engines is by the use of inertia starters, which require only the same effort whatever be the engine stiffness or temperature conditions prevailing. These starters are made either for operation by hand or by electric motor, the essential principle involved being first, the storage of energy in a small free-running flywheel, and, secondly, the utilisation of this energy for rotating the engine crankshaft after removal of the externally-applied power. Inertia starters are extensively used for aeroplane engines as, in addition to advantages already mentioned, they have minimum weight in proportion to capacity, and give a high initial engine cranking speed (about 80 r.p.m.).

These starters are manufactured by the British Thomson-Houston (Co., Ltd., Coventry, this company holding the sole manufacturing and welling rights for Great Britain of the Eclipse Machine Company's inertia starters, and are available either or operation by hand-cranking or by electric motor. The hand inertia starter is operated by turning a crank handle, which is inserted in the spiral slot provided in the end of the crank extension. Hand cranking the starter usually for between 15 and 30 seconds, with gradual acceleration until a speed of about 80 r.p.m. is reached brings the barter flywheel up to a rotation of some 12,000 r.p.m., when removal of the crank handle and a pull on the operating rod engages the flywheel with the engine crankshaft through determined torque to suit the engine to which the starter is applied.

Mechanically, the electric inertia starter is the same as the hand inertia starter, there being an electrical attachment bolted to the starter flywheel housing. Acceleration of the flywheel to operating speed is obtained by means of an electric motor, and it should be mentioned that as the current required is independent of the atmospheric temperature, the combined weight of starter and battery is the lowest possible — an important consideration on aeroplanes.

Moreover, one-man starting from the pilot's cockpit is available, so that the engine can be cranked while the 'plane is in mid-air, and, in the event of a forced landing, the ability to start the engine conveniently without manual or external assistance is highly desirable. A push-and-pull switch in the cockpit gives remote control of the starter through a solenoid switch mounted integrally with the electric motor. Pushing the switch button closes the electric circuit and allows the motor to accelerate the starter flywheel to operating speed, the time required usually being about five seconds. As soon as this speed is reached a pull on the switch button opens the electric circuit to the motor, and further pulling on the switch button acts on the operating lever of the starter through the medium of a cable or rod fastened to the end of the switch button rod, so as to engage the rotating starter drive jaw with the engine crankshaft. As soon as the engine fires, the starter jaw is automatically disengaged from the engine crankshaft by means of a quick thread. The operator then releases the switch button, and a return spring brings it back to its normal neutral position.

In addition to the electric attachment a hand-cranking shaft is provided so that the electric inertia starter can also be used as a hand inertia starter. As an automatic device is provided for connecting the electric motor armature to the flywheel only when the electric motor is running, the starter is relieved at all times of any losses due to brush friction, and any excessive drag on the starter when it is operated by hand is avoided."

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Vitus
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Re: Eclipse Inertia Starter

Post by Vitus » 06 Jul 2018, 13:19

I think I read somewhere that the direct electric starter was an upgrade option for the Vega, but I can't recall where I got it from. However I did see the startup procedure performed by Post (the video of him landing and taking off in Berlin) and always pondered whether to put a inertia starter in. It's quite a bit of work though...

The flywheels make such a great sound:
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Re: Eclipse Inertia Starter

Post by Vitus » 06 Jul 2018, 13:22

For the electric version of the inertia starter I'd need to know what the controls look like and how they operate. I could imagine that the control that activates the clutch between flywheel and crankshaft is some sort of lever of pulley?
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Tailspin45
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Re: Eclipse Inertia Starter

Post by Tailspin45 » 06 Jul 2018, 17:37

Two switches. One is "Energize" which spins the flywheel, one is labeled "Engage." No clutch, no lever, no pulley. The solenoid does the job.

Early AT-6/SNJ had a foot pedal on the floor between rudder pedals to do the job (similar to the illustration above). Later just had two switches on the right subpanel. Then just one switch when direct drive was introduced and the starter turned the engine with no flywheel.
Last edited by Tailspin45 on 06 Jul 2018, 22:28, edited 1 time in total.
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Re: Eclipse Inertia Starter

Post by Vitus » 06 Jul 2018, 20:49

Tailspin45 wrote:
06 Jul 2018, 17:37
Two switches. One is "start" which spins the flywheel, one is labeled "Engage." No clutch, no lever, no pulley. The solenoid does the job.
That doesn't make much sense to me. The inertia starter uses the kinematic energy, stored in the flywheel, to crank over the engine. So you need a button or switch to close the circuit for the low-power electric motor that spins up the flywheel. But to make the connection between flywheel and main shaft, there needs to be a mechanical connection. That's why I thought a mechanical pulley or something similar would be an obvious choice. A solenoid would work, sure, but it doesn't seem a logical choice, considering that you don't want to waste your battery power to create this mechanical link.
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Tailspin45
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Re: Eclipse Inertia Starter

Post by Tailspin45 » 06 Jul 2018, 21:03

The battery power is expended mainly to spin up the flywheel, as you say, and it doesn't take much to engage the solenoid--it's held in place by dogs once engaged. All the work is done by the inertia stored in the flywheel. Let me see if I can find a diagram...
Last edited by Tailspin45 on 06 Jul 2018, 22:33, edited 1 time in total.
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Re: Eclipse Inertia Starter

Post by Tailspin45 » 06 Jul 2018, 21:44

Only passing reference to inertia starter (the hand crank kind), but good info on many topics from an expert
http://www.sandersaeronautics.com/libra ... ec2011.pdf

Lots more off-topic stuff at
http://www.sandersaeronautics.com/links_library.asp

Here's the diagram I was looking for. This has a single two-pole switch instead of two switches. But same principle.

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Re: Eclipse Inertia Starter

Post by Tailspin45 » 06 Jul 2018, 22:21

The rest of the pages, from Pilot's Powerplant Manual, US Department of Commerce, 1942. Note that they do refer to a push/pull knob to engage the flywheel if the engine is ahead of the pilot. AT-6 didn't have it, but would make sense in the Vega.

Image

Image

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Last edited by Tailspin45 on 06 Jul 2018, 22:49, edited 1 time in total.
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Re: Eclipse Inertia Starter

Post by Tailspin45 » 06 Jul 2018, 22:35

Seems to me I've run across the Aircraft Engine Historical Society referenced here someplace, but just in case:

http://www.enginehistory.org
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Jarek
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Re: Eclipse Inertia Starter

Post by Jarek » 06 Jul 2018, 23:36

It looks like simple electric 2-position switch. This comes from Sirius, but it is original, it went to museum in late '30, so it is a good candidate I think. So most probably it was push/pull type as described in the magazine.

Switch:
starter.png
starter.png (153.58 KiB) Viewed 381 times
Look from the back (notice one disconnected terminal)
starter_back.png
starter_back.png (94.06 KiB) Viewed 381 times

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