Small repair....

[Pennywise]

Hello all, I live between Renfrew and Arnprior, Eastern Ontario and have some tools but not a milling machine. (A old unimat that was a gift, for example)
Here's the problem, I have an attachment for my outboard called a trolling plate that keeps breaking at the same point,the part that breaks is called a "locking bar"
It's made from glass filled nylon and I want to replace it with an aluminum piece.
I have the aluminum rod stock 11 mm dia. and need to mill 2 flats down to a cross section of 7.65 mm, that's it. The ends I can do myself, the photos should show my problem.
I was hoping there was a local hobby machinist nearby that could earn some cash, as the commercial shop near me would likely have a minimum charge that would make such a job too expensive for me.
I have enough material for two locking bars as I have two trolling plates with the same defect.I have some welding equipment and do auto repairs if someone with a milling machine would like to trade repair jobs....

 

[Susquatch]

I'm too far to help directly, but I have some questions that might be helpful to you. I know what a trolling plate is.

Why does it break? And when does it happen? Is the plate aluminium? Can you post a photo of a broken part?

Would a round stainless bar the same diameter as the slot work? It wouldn't need the flats and would still be stronger than the original.

In either case, you have to make sure that a strong rod doesn't break the next weakest link - the plate slots.

Is it designed to release when you throttle up the motor, or is that what breaks it?

 

[Pennywise]

The plate is plastic, in fact the whole device is.

I don't know why it breaks, it happens under water while in use so a clear view is impossible.

Yeah, the photos in my first post should show everything.

I figure the flats are there for a reason, I'm mechanically inclined but not an engineer.

If I had to guess if the bar was round it would spin and the holes that the spring engages would torque/spin and bend the wire, eventually snapping it/wearing it out.

A single lever engages/disengages the plate, so when I trailer it it's in the up position, same as for when I just travel on the water, but when I need to troll I pull the lever up with a lanyard, (engine in neutral) and the plate is pulled down by 2 springs and locks.

When I finish trolling I stop, put the engine in neutral pull the lanyard which unlocks the plate then put the prop in gear and a touch of gas will pop the plate back up and it latches automatically.

Years ago we ran larger motors with the bigger versions of these plates which were all aluminum and while a really careless operator would bend them by gunning the engine while in the "down" position you had to be a real idiot to do any real damage, all of mine survived years of use, until I started with the smaller engines and the plastic trolling plates.
In my opinion the smaller trolling plates should be aluminum as well, but the tooling and material is cheaper when you go to glass filled nylon and ABS, so the profit incentive drives that decision, I suppose.

 

[Susquatch]

Just noodling.

If you pulled the rope to release the plate and then throttled up to lift the plate, but the plate didn't actually fully release, I think the bar would break. Perhaps this is what is happening.

But if you replace the bar with stronger aluminum or stainless, and it didn't break or release, the plate would break instead.......

What keeps the flats of the bar aligned with the flats in the plate? Why are flats required?

 

[Dusty]

@Pennywise said, Here's the problem, I have an attachment for my outboard called a trolling plate that keeps breaking at the same point, the part that breaks is called a "locking bar" It's made from glass filled nylon and I want to replace it with an aluminum piece.

Although I'm unsure what a trolling plate and locking bar is used for I CAUTION you on using aluminum for the following reasons. Believe we all understand structure fatigue and failures on aircraft, that said my working years around military aircraft gave me some insight into using stronger materials being used to replace structure that was fatiguing and cracking. More often than not replacing materials with some thing stronger frequently simply transferred stress somewhere else on a war bird.

Rather than using aluminum why not try Duralin (also known as Acetyl or Delrin) is a unique material with an extraordinary combination of strength, stiffness, dimensional stability, fatigue resistance, and low friction.

My suggestion for what it's worth, just saying!

Better yet can you determine the cause of the locking bar failure?

 

[Pennywise]

@Pennywise said, Here's the problem, I have an attachment for my outboard called a trolling plate that keeps breaking at the same point, the part that breaks is called a "locking bar" It's made from glass filled nylon and I want to replace it with an aluminum piece.

Although I'm unsure what a trolling plate and locking is used for I CAUTION you on using aluminum for the following reasons. Believe we all understand structure fatigue and failures on aircraft, that said my working years around military aircraft gave me some insight into using stronger materials being used to replace structure that was fatiguing and cracking. More often than not replacing materials with some thing stronger frequently simply transferred stress somewhere else on a war bird.

Rather than using aluminum why not try Duralin (also known as Acetyl or Delrin) is a unique material with an extraordinary combination of strength, stiffness, dimensional stability, fatigue resistance, and low friction.

My suggestion for what it's worth, just saying!

Better yet can you determine the cause of the locking bar failure?

I appreciate the caution, Dusty, I worked for DND as a civilian a long time ago stocking spares for all manner of equipment , from the Frigates in the 90's to F18's and the once thing they trained us to recognize was the "consequence of error".

In this case a failure in the assembly due to an upgraded/stronger component isn't a deal breaker.

No injury to worry about as the "RUD" (rapid unplanned disassembly) if any would take place 2 feet under the water and 5 feet from the nearest human,at speeds under 5km per hour.

My best guess as to the failure is poor choice of material for a part that is under a lot of stress.
Other users have complained to the manufacturer about how fragile this item is.

And my past experience with the larger ( aluminum) trolling plates used on 50+ Hp outboards with little issue/problem tends to make me favor that material.

You are probably familiar with the first jet airliner the British fielded?
The Comet, metal fatigue due to the constant flexing of the aluminum skin when pressuring/depressurising, and the Boeing 737 over hawaii that came in and landed with half of its upper fuselage missing? Aloha flight 243.

 

[Pennywise]

Just noodling.

If you pulled the rope to release the plate and then throttled up to lift the plate, but the plate didn't actually fully release, I think the bar would break. Perhaps this is what is happening.

But if you replace the bar with stronger aluminum or stainless, and it didn't break or release, the plate would break instead.......

What keeps the flats of the bar aligned with the flats in the plate? Why are flats required?

Yeah, I could speculate as to why it breaks, but the fact is it does and the weak point is the glass filled nylon part, I've had experience with this stuff years ago and it's great, strong and durable, but maybe a poor choice for this application.

My guess is it's used because it's cheaper than aluminum, both to buy and manufacture.

The slots in the base match the slots in the plate, it's seen in photo #1 I think.

Like I said earlier the slots and the flats are to keep the bar from spinning and stressing the springs by virtue of the holes in the bar.

 

[Pennywise]

So, no local member has risen to the challenge with an offer to mill flats into my aluminum round stock? a pity.
I drove over to the local machine shop after lunch but it being Friday it looks like they closed up early.
Oh well they would probably say something like "Sure, our minimum for any small job like this is a Gazillion Dollars" Lol!

 

[ChazzC]

So, no local member has risen to the challenge with an offer to mill flats into my aluminum round stock? a pity.
I drove over to the local machine shop after lunch but it being Friday it looks like they closed up early.
Oh well they would probably say something like "Sure, our minimum for any small job like this is a Gazillion Dollars" Lol!

Have faith: while it’s been 6 hours since your initial post, it is a week day and not everyone checks the Forum during the day. I would be surprised if someone doesn’t pop up in the next few days.

For a local shop, look for a one-person operation: when I was looking for help getting a large diameter rod cut into a couple of slugs, the shop I could walk to talked $50/hr and minimums. I then found a guy who was interested in what my project was and cut the stock for free. He’s since done some other odds & ends and I’ve paid him more than what he asked. He also lets me scrounge through his offcuts (do you know how hard it is to find large 12L14 square stock?).

 

[Dusty]

@Pennywise said, You are probably familiar with the first jet airliner the British fielded? The Comet, metal fatigue due to the constant flexing of the aluminum skin when pressuring/depressurizing, and the Boeing 737 over Hawaii that came in and landed with half of its upper fuselage missing? Aloha flight 243.

Hear what you are saying, in !959 wife and I flew overseas in an RCAF military Comet, I was well aware of the issues with the Comet's airframe structure failures with windows popping out although my wife wasn't even though she was six months with our first child. By this time the problem was fixed so de Havilland said.

Good luck with your project.

 

[Pennywise]

If you ever had occasion to land at RCAF Rockcliffe base in Ottawa during that space in time
you might've had a chance to run into my father?
He was a tool & die maker there, name was Gordy McWade

 

[Dusty]

If you ever had occasion to land at RCAF Rockcliffe base in Ottawa during that space in time
you might've had a chance to run into my father?
He was a tool & die maker there, name was Gordy McWade

Unfortunately no I never landed at Rockcliffe although I heard lots of stories about the base from the old guys.

Speaking of tool and die makers, my father was a die setter in Hamilton where I was born with Stanley Steel of Canada. Yes the same company who made saws, wood planes, hinges etc.

 

[Susquatch]

So, no local member has risen to the challenge with an offer to mill flats into my aluminum round stock? a pity.

Keep the faith and have patience. Most members visit the forum on a rough schedule. I'd give it at least 2 days. There are about a half dozen Ottawa members. Maybe search on Ottawa and then give them a direct shout by PM. That will cause the system to generate an email notification to let them know you reached out to them.

If nobody local will do it, you can always ship it to me and I'll do it free. Maybe with shipping that will wash.

Like I said earlier the slots and the flats are to keep the bar from spinning and stressing the springs by virtue of the holes in the bar.

I didn't know the springs went through holes in the bar. I wouldn't have done that. I'd have put a groove in the bar for the springs to ride so rotation didn't matter.

The flats might be cocking and binding and preventing the plate from fully disengaging. Then when you hit the throttle it breaks.

 

[jorogi]

What length is the part ?

 

[Pennywise]

9 inches long.

 

[Pennywise]

Keep the faith and have patience. Most members visit the forum on a rough schedule. I'd give it at least 2 days. There are about a half dozen Ottawa members. Maybe search on Ottawa and then give them a direct shout by PM. That will cause the system to generate an email notification to let them know you reached out to them.

If nobody local will do it, you can always ship it to me and I'll do it free. Maybe with shipping that will wash.



I didn't know the springs went through holes in the bar. I wouldn't have done that. I'd have put a groove in the bar for the springs to ride so rotation didn't matter.

I understand, a good designer will try different versions, it's possible they tried that and it tended to slip off? or the nipple formed by the groove at the end was a weak(er) point than a hole?

The flats might be cocking and binding and preventing the plate from fully disengaging. Then when you hit the throttle it breaks.

Yeah, thanks. I was attempting a little humour...it doesn't always translate over the 'net, so much is driven by facial expression/body language.


After the first device pooped the bed I was careful to check for that scenario of binding and after a few cycles all seemed well then it would come up mangled....

Thanks for your offer to do the machining, I will take you up on that if no one closer by steps up.

 

[Pennywise]

Unfortunately no I never landed at Rockcliffe although I heard lots of stories about the base from the old guys.

Speaking of tool and die makers, my father was a die setter in Hamilton where I was born with Stanley Steel of Canada. Yes the same company who made saws, wood planes, hinges etc.

Too bad, that would've been a neat coincidence.
I saw my first Starfighter at a Christmas party there ( I was 4 years old) my first reaction was to ask my father if they cut the wings off to fit it into the building.....
I still have some old Stanley saws handed down to me, still good for it after a few passes of a file.

 

[OliverTO]

If you need it right away, the flats could easily be put on that 9" rod with a hand file or belt sander.

 

[Pennywise]

If you need it right away, the flats could easily be put on that 9" rod with a hand file or belt sander.

Yeah I did think of that, I've done my fair share of what my buddy calls "Hillbilly Machining"
but this device seems to be prone to jamming which may be part of the failure mode so I want
to reduce any possibility of jamming.
Another way to do it would be to use a wood router with a carbide cutter to cut the radius but I'd need to start with a sheet/bar of 7.6 mm aluminum, then count my fingers, lol!

 

[jorogi]

9 inches long.

Flats are full length 180 degrees apart ?
How critical is the 11mm diameter, would 12.86mm work ?
Would 6061 T6 or 2024 T3 work ?