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Starter springs coming loose

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Starter springs coming loose

Post  ThermalSniffer on Fri Feb 17, 2017 4:54 pm

Running in a brand new black widow this evening I was quite annoyed to have two different types of starter spring setups come loose and damage the engine's anodising in the process.

The first setup is the one that came with this 1988 engine, a hexagonal driver with a matching grey plastic catch plate. After that spring came loose I took things apart and installed a standard circular bee style driver and a brand new prop catch type spring. One of the ones Bernie sells with the catch that points upward when installed. That spring also came loose.

I don't have an electric starter but it is starting to sound tempting. I haven't run many different Cox engines but, even so, this is the first where this has happened to me. Anyone else have this happen and what's the fix?

I am hooking the springs behind the cylinder then I am also using the front of the fuel tank to pinch it in place before tightening the tank screws back down.
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Re: Starter springs coming loose

Post  Cribbs74 on Fri Feb 17, 2017 5:10 pm

Are you snapping it into the groove on the crankcase?

While an electric starter sounds nice, it will slowly destroy your crankcase.
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Re: Starter springs coming loose

Post  ThermalSniffer on Fri Feb 17, 2017 5:28 pm

The groove between cylinder thread lip on the crankcase and the tank? If so, yes I am. I am loosening the tank slightly, slipping the spring in there and then retightening the tank screws making sure the spring gets trapped as I do so. If that is the correct method then it could just be this engine I suppose.
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Re: Starter springs coming loose

Post  NEW222 on Fri Feb 17, 2017 6:34 pm

Wierd I say. It most definately sounds like you got it located in the right place. Maybe if possible, could you post a picture from the backside of the spring when attached as you had been doing? It may help see something. But without a picture, is there possibly room on the spring to give it a little more of a tighter radius where it attaches? Maybe it is spread a little from where it should be?
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Re: Starter springs coming loose

Post  roddie on Fri Feb 17, 2017 10:12 pm

With reed-valve engines.. there should be ample clearance for the spring to hook-around the boss on the case at the base of the cylinder.. whether you install the spring first.. or last. The "back-end" is not meant to clamp the wire.

Please excuse these grimy examples..

Cam-style



Zero-drag



They've always stayed in position for me once installed. I can't speak for repro-springs. Mine are genuine Cox parts.. and fit tightly. I will add that I only wind-them "one-turn". Any more than one turn is unnecessary.. and will distort the spring.. as well as risking a deeper-cut to your finger; should you slip.

I've used electric-starters in conjunction with a Tee Dee-style aluminum spinner. It's VERY important to place a few drops of light-oil behind the prop drive-plate and flip the prop a few times to work it in.. before connecting the glow-plug. Go easy with an electric starter. Use "light-pressure" and "short-bursts". This will greatly reduce heat build-up from friction.

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Re: Starter springs coming loose

Post  balogh on Fri Feb 17, 2017 11:40 pm

I second to what Roddie said, do not wind the spring over 1 or max 1.25 turns. For electric starter use you may want to put a stainless steel washer between the prop drive plate and the crankcase to reduce abrasion. Bernie sells them in different sizes.
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Re: Starter springs coming loose

Post  ThermalSniffer on Sat Feb 18, 2017 1:52 am

Ok guys you have picked up on one of my bad habits. I tend to pull the prop back through as many turns as the spring will allow before I release it. Could be what's happened here.
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Re: Starter springs coming loose

Post  KariFS on Sat Feb 18, 2017 2:51 am

I've found that about 3 quarters of a turn is enough for the cam style.

I've also noticed that some repro springs (again cam style) are a bit loose and the radius of the coil is just a little too big for the hook to catch the cam "first time, every time". Not sure whose manufacture they are, maybe they are Estes or something, but anyway different compared to the few genuine oem springs from the '80s that I have.

A few used engines, that I have received, have had the spring would up tight around the crankcase neck, clearly a sign of "winding it up too tight".

I also have an early BW with the colour worn off the neck, it had the original "wound too tight" spring on it which I replaced. I personally think that signs of use add charm to a runner Smile

I don't think I have ever had a spring come loose off the cylinder base though Huh... I'll need to check mine for that too. Maybe you can improve that situation by pre-forming that part of the spring into a tighter radius?


Last edited by KariFS on Sat Feb 18, 2017 4:31 am; edited 1 time in total
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Re: Starter springs coming loose

Post  balogh on Sat Feb 18, 2017 3:51 am

probably the most authentic source on how to use the spring starter: an excerpt from the COX leaflet "Bob and Jack start their COX Thimble-Drome Plane":

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Re: Starter springs coming loose

Post  gcb on Sat Feb 18, 2017 5:40 am

KariFS wrote:I've found that about 3 quarters of a turn is enough for the cam style.

I've also noticed that some repro springs (again cam style) are a bit loose and the radius of the coil is just a little too big for the hook to catch the cam "first time, every time". Not sure whose manufacture they are, maybe they are Estes or something, but anyway different compared to the few genuine oem springs from the '80s that I have.

A few used engines, that I have received, have had the spring would up tight around the crankcase neck, clearly a sign of "winding it up too tight".

I also have an early BW with the colour worn off the neck, it had the original "wound too tight" spring on it which I replaced. I personally think that signs of use add charm to a runner Smile

I don't think I have ever had a spring come loose off the cylinder base though Huh... I'll need to check mine for that too. Maybe you can improve that situation by pre-forming that part of the spring into a tighter radius?

If I remember correctly, the spring starter was invented by Mr. Davis of DDD. He sold the first ones to Cox, then I believe he sold the rights to Cox.

I removed some starters from my engines early on. I figured if I can't hand-start it I have a problem (bull-headed perhaps?). I finally accepted them.

George
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