# Roll your own



## torch (Dec 8, 2014)

I don't know if anyone else here likes to make their own repair parts, but here's my recent effort. 

The whistle rectifier was just about shot on my KW, so I took it apart to upgrade to a modern silicon diode. That's when I discovered the pick-up rollers were shot. The "bearing" holes were sloppy around the rivet "axles". They had obviously stopped rotating and started sliding, wearing a flat spot on one side of each roller. 

I'm not sure why Lionel made them out of graphite in the first place. After all, they roll, not slide. Graphite is used on sliding brushes (eg: electric motors) because it's self-lubricating. Unfortunately it's also soft and less conductive than most metals. I decided to make new rollers out of 660 bearing bronze. 











Steel rivets also seemed a bit silly. What's the point of the copper frame it's riveted to? So I elected to make my own from brass:










Here's the finished result, with one assembled. I held a 1 thou clearance and applied a thin smear of electrically conductive grease. They roll very nicely. 










For the diode, I used a stud type, the idea being that I could bolt the existing bus bar to the eye in the diode. I made a delrin spacer to keep it centred in the original location, but then discovered the diode would hit the windings. I had to remove the spacer and massage things into place, adding some heat-shrink to the bus bar to prevent it from contacting the resistor wire. 










A regular old #6 bolt & nut would have been sufficient, but since I was at the lathe, I made a nice brass one with a shoulder sized to fit the holes and a couple of washers. 










It works well. Too well. First time I hit the whistle, it burned out the wire from the pickup on the tender... hwell: (it was a week spot from years of bending back and forth)


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## rkenney (Aug 10, 2013)

Very nicely done!!:smilie_daumenpos:

So, when will you be offering these for sale?


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## servoguy (Jul 10, 2010)

I don't believe making the rollers out of metal is a good idea. The rollers often short two windings together. The resistance of the carbon roller limits the current under these conditions. The metal roller does not limit the current and could cause the windings to get very hot.


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## gunrunnerjohn (Nov 10, 2010)

Bruce is right on target, as usual! This is really a BAD idea, as you're shorting two windings much of the time. The carbon rollers are designed to have a higher resistance, so the short through the resistance of the roller is not a big issue, but your brass one will provide a low resistance connections.


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## rkenney (Aug 10, 2013)

Looks like you were shorting more than two coils with that carbon slider arrangement.

Since you are the only one with any empirical knowledge of this specific application you will have to be the one to determine how well it works.

There are a few transformers with wipers that contact more than one coil.

It is a nice piece of work. Let us know how it runs over the long haul.:appl:


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## servoguy (Jul 10, 2010)

To finish this discussion, I opened up my ZW and made some measurements. I measured the resistance of a single turn of the winding and also of the roller. The roller roller has wear marks that correspond to the coils of the transformer secondary. I measured between two wear marks and got 1.35 ohms. I measured the resistance of a single turn of the secondary and got 0.22 ohms. I counted 46 turns on the secondary winding. The low voltage of the secondary is 6.5 volts, and the high voltage is 20 volts. The voltage across each winding is (20-6.5)/46 = 0.294 volts/winding. The current with a dead short across a winding is 0.294/0.22 = 1.33 amps. The current with the carbon roller is 0.294/1.335 = 0.218 amps. Power dissipation with the metal roller is I^2*R. For the metal roller is is 1.33^2*0.22 = 0.39 watts all of which is dissipated in the winding. For the carbon roller it is 0.218^2*1.335 = 0.063 watts most of which is dissipated in the carbon roller. 

I made measurements of the resistance and voltage of the individual coils of the secondary, and they came close to the calculated numbers.


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## servoguy (Jul 10, 2010)

BTW, I opened up my ZW a few days ago because the whistle control was not working properly. I noticed some of the rollers were not turning properly, so I oiled them with motor oil They now turn perfectly.


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## servoguy (Jul 10, 2010)

One more thought on the brass roller. Brass is harder than copper, and you may get some wear of the winding that is not good.


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## torch (Dec 8, 2014)

servoguy said:


> I don't believe making the rollers out of metal is a good idea. The rollers often short two windings together. The resistance of the carbon roller limits the current under these conditions. The metal roller does not limit the current and could cause the windings to get very hot.


I thought about that -- actually thinking in terms of arc pitting as the roller approached the next winding. There are approximately 50 windings. The range is from approximately 6 volts to 20 volts, so about 0.28 volts per winding. 660 bearing bronze is more conductive than graphite, but still only 1/4 as conductive as copper. 

I can't see any visible arcing in operation, but I guess time will tell. If I run into problems down the road I'll come back here and eat crow. 

Edit: The rollers are not brass. They are 660 bearing bronze. I picked it because it is highly machinable, ensuring I could polish it to a very smooth finish. I don't think it's obvious from the photos, but the edges of each roller are rounded and polished. It's a high-leaded tin bronze with excellent anti-friction properties so even if it does stop rolling, it should not damage the copper windings. Just the rivets are brass. 

As for selling them, that was not my plan. I just thought I'd throw out what I did in case someone else was interested.


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## BillCN (Jan 6, 2013)

.
WOW
Fantastic workmanship!
I am wondering why you have a metal lathe?
I have an old ATLAS...probably from the 30ies...that my Dad had....
The problem is that I can't find any practical use for it.:appl:


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## torch (Dec 8, 2014)

BillCN said:


> I am wondering why you have a metal lathe?


So I can make square things round. I also have a mill for when I need to make round things square. :laugh:

Seriously, I like to tinker with almost anything mechanical, but particularly antique outboards and old motorcycles. I often have to make my own parts and/or special tools because stuff just isn't available anymore. So I set up a small home machine shop in one corner of the garage. 



> I have an old ATLAS...probably from the 30ies...that my Dad had....
> The problem is that I can't find any practical use for it.:appl:


Those old Atlas lathes are quite popular amongst home machinists. Do you still have your Dad's tooling? The tooling (including meterology) is just as important as the machine itself. If you still have that then you are all set to start making things. Although when I first started, I mostly made mistakes... :laugh:


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## Big Ed (Jun 16, 2009)

torch said:


> So I can make square things round. I also have a mill for when I need to make round things square. :laugh:
> 
> Seriously, I like to tinker with almost anything mechanical, but particularly antique outboards and old motorcycles. I often have to make my own parts and/or special tools because stuff just isn't available anymore. So I set up a small home machine shop in one corner of the garage.
> 
> ...



Excellent work torch. :smilie_daumenpos:
Nice to have a lathe around. I hope it works out.

The only lathe I ever used was way back in the high school wood shop.
I made a nice salad bowl. 
The lathe process didn't take that long, for the rest of the year all I heard was it needs more sanding Ed. I think I spent most of the school year just sanding it.

Got any old Evinrudes?:smilie_daumenpos:


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## BillCN (Jan 6, 2013)

torch said:


> Do you still have your Dad's tooling? The tooling (including meterology) is just as important as the machine itself. If you still have that then you are all set to start making things. Although when I first started, I mostly made mistakes... :laugh:


.
By tooling...do you mean the cutting bits, etc.??

Ya I still have lots of those....many that he made himself for a special purpose.


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## sjm9911 (Dec 20, 2012)

Cutting metal is a lost art. Nice work , but above my pay grade. I can see how that skill set could have advantages with model trains . 
Ed, we had woodshop and metal shop in high school. Unfortunately they have been cut years ago for computer and art classes. Like I said its lost art.


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## torch (Dec 8, 2014)

BillCN said:


> .
> By tooling...do you mean the cutting bits, etc.??
> 
> Ya I still have lots of those....many that he made himself for a special purpose.


Yes, the lathe bits are a big part and most HSS bits are hand-ground on a bench grinder to suit the application, although there are a few standard shapes (RH, LH, facing, parting, threading, boring etc.) that are used for 90% of all the work. Custom bits are ground for "form" work, like round-overs, coves, o-ring seats, circlip grooves, etc. You can buy insert tooling, usually carbide, but they get expensive fast and may require more rigidity and/or power than usually found in a small bench lathe. 

Tooling also includes things like tailstock chucks, lathe dogs, live and dead centres, etc. An important part of the tooling is the meterology -- dial indicators, calipers, micrometers, etc. You can't do precision work without the ability to measure accurately. In the case of the above example, I used a micrometer to measure the rivet diameter and a set of minus pin gauges to measure the hole (minus pin gauges come in one thousandths increments and are 2 ten thousandths smaller than the marked diameter, so they *just* slide in the hole.) A broad range of tooling can cost as much as the lathe itself, so if you have the tooling you are really in good shape to get started. 

This is not really the place to delve deeply into setting up a home machine shop. If it is something that interests you, I highly recommend the Chaski home machinist forum. The guys there are highly skilled, very friendly and very helpful. I have learned a lot from that forum over the years.


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## BWA (Jun 16, 2012)

Actually, when the roller touches two adjacent windings, it doesn't form the type of short you guys are thinking about. Basically, all it's doing, is removing one coil of winding from the set of windings, and, shouldn't produce any large current flows.

More like isolating that coil from the circuit rather than shorting out the circuit itself.

To eliminate any arching problems, just oil the roller to winding contact path, that should stop any pitting that may or may not occur. I do this on all my variable transformers, including my two KWs. This really cuts down on the roller/winding wear, and makes operation very smooth.

I also have various lathes and milling machines. Here's my Clausing Milling machine, being used to modify a TR6 Bearing Hub Puller.......


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## torch (Dec 8, 2014)

Nice. Do you make parts for your trains as well?

Unrelated to trains: Is that a tapping head, or where you holding the tap in a Jacob's chuck? Also, what's the small motor to the right, below the table? I doesn't look like it's in the right place for a power feed.


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## torch (Dec 8, 2014)

big ed said:


> Got any old Evinrudes?


Several. From 1914 up to about mid-60's. I have mostly OMC, some Scott-Atwater and a couple of Mercs.


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## BWA (Jun 16, 2012)

Not a tapping head, just a keyless chuck. I turn the Mill on, use the manual quil feed to drop the tap into the hole, once, it starts to bite, and, feed itself, I turn the mill off. By the time the mill stops, it has run the tap about the proper depth. I then just run the mill backwards to drive the tap out.

Pretty crude, but, it works fine.

The motor gizmo, is the drive head for my cylinder head valve seat cutting tool. Spent most of my adult life servicing and restoring British Automobiles, ended up with lots of neat machine tools over the years. About the only thing I couldn't do myself, was, bore the cylinders for oversize pistons. Everything else, I did myself.


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## gunrunnerjohn (Nov 10, 2010)

BWA said:


> Actually, when the roller touches two adjacent windings, it doesn't form the type of short you guys are thinking about. Basically, all it's doing, is removing one coil of winding from the set of windings, and, shouldn't produce any large current flows


Sorry, but that's clearly incorrect. The bane of transformers or other stuff like motors is a shorted turn or turns. If you have a dead short between two windings in a transformer, either in the primary or secondary, a lot of current will be flowing in that shorted turn, usually with disastrous results. Things will get VERY hot in a hurry around the shorted turn.

Since I'm anticipating some resistance to this answer, here's one of many references on the issue.

Quote from: Learn About Electricity, AC Theory



> 2. The transformer has suffered an internal shorted turn. This means that the insulation between two turns of a winding has broken down. The effect of this is to create a winding of a single turn. The effect of this is to create a winding of one turn. The transformation ratio is now enormous! Imagine a transformer with a 1000 turns on its primary and 100 turns on it secondary, suffering a shorted turn on the secondary winding. The turns ratio has just changed from 10:1 to 1000:1! The result is very little secondary voltage but enormous current. In this case again the only solution is replacement.


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## servoguy (Jul 10, 2010)

John, you are absolutely correct. In fact, the failure mode of motors and alternators is a shorted turn. The windings in motors and alternators are bound together with lacing cord and glued together to prevent motion between windings. Motion between the windings will cause the insulation on the wire to be rubbed off. When the insulation fails, the magic smoke gets out and the motor or alternator is either junk or must be rewound. There are forces between adjacent windings caused by the electromotive force of the magnetic field.


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## servoguy (Jul 10, 2010)

Include transformers in my previous post along with motors and alternators.


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## torch (Dec 8, 2014)

gunrunnerjohn said:


> I'm anticipating some resistance


Punny. Very punny. :laugh:

But I have to admit that you raise some very interesting points, which are alluded to in this patent application: http://www.google.com/patents/US4189672

Obviously, this is a well-known issue in high-power variable transformers. The application mentions an upper limit of 10KVA (about 10,000 watts), but does not mention any lower limit in the definition of "high-power". 

But there must be a lower limit. There are many train transformers that use nothing more than a simple brass arm and contact to sweep the secondary windings. (I'm pretty sure my RX is one of those, and it was rated 100 watts.) Perhaps the difference lies in the magnetic coupling between the winding and core? The KW (and presumably the ZW, which uses the same rollers) can provide considerably more power and perhaps have closer magnetic coupling to improve efficiency. 

On the other hand, how many people have opened up one of these and found the roller worn to a flat spot so that the copper shoe that holds the roller has actually been making contact? Other than the obvious friction damage to the copper wire windings, has that resulted in any damage to the transformer? Obviously this is not a cause of instant death even for the large transformers, but perhaps it could lead to premature aging -- increased heat breaking down the lacquer insulation over time. 

I'm away for the weekend, but next week I'll try to perform a little experiment and measure the actual current flow of shorting one winding to the adjacent one. I'll set one roller on the peak of a winding, the other roller at the peak of an adjacent winding, and measure the current between A and B. 

If the current is in excess of, say, the current drawn by my dual-motor FM at full throttle, then it might be a problem. If the short-circuit current is less, then the transformer should have no problem handling it, right?


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## gunrunnerjohn (Nov 10, 2010)

The same principles apply to the smallest transformer as to the largest.

Try this experiment. Take two test probes and use them to get a good contact between adjacent turns on the transformer. Short the other ends and use a clamp-on ammeter to measure the current flow in the shorted turn. I suspect you're going to have some hot leads in your hands in short order.

One only has to take a look at the Weller 100/140 soldering gun to see what currents can flow in a shorted turn, which is basically what they use to heat the tip. Since my clamp-on only measures up to 50A, I can't tell you what it is, suffice to say that it pegs the meter with authority the instant I hit the trigger. Resistance soldering depends on the same principle.

The key here is how good a connection there is between the turns, a true dead short will allow some immense currents to flow, limited only by the gauge of the wire in the secondary.


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## torch (Dec 8, 2014)

gunrunnerjohn said:


> Try this experiment. Take two test probes and use them to get a good contact between adjacent turns on the transformer. Short the other ends and use a clamp-on ammeter to measure the current flow in the shorted turn.


Essentially what I am proposing. By placing the roller of the A throttle on one winding, and the roller of the B throttle on an adjacent winding, measuring the current of a short between the A and B terminals provides a measurement of the current between the two windings. The advantage of using the rollers is that it requires fewer hands when taking the measurement. The disadvantage is that the electrical path through the rollers will be greater than the distance of one roller bridging the two windings, so in theory the resistance will be higher. However, you would need a micro-ohm meter to measure it. 

It would also be interesting for someone with graphite rollers to replicate the experiment for comparison.


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## gunrunnerjohn (Nov 10, 2010)

I think you'll find the resistance to be MUCH higher going through the two rollers, the arms and hub contacts, and back to the rear terminals. It will be closer if you connect directly to the two arms, then you only have the roller to arm contact resistance.

Whatever the results of the one-time experiment is, my previous comments are still correct, a shorted turn in a transformer is a big deal!

The reason you get away with a partial short with the graphite rollers is the very small voltage differential between the adjacent windings. Lower the resistance and you increase the current.

Here's an interesting page on variacs and why they use graphite rollers and the specific properties of graphite that allow the shorted turns to be a minor factor.

Transformers - The Variac



> Fortunately, graphite is an anisotropic material, having very different resistivity depending on the direction of current vs. the alignment of the graphite planes [1]. A direct measurement across the brush of the Powerstat transformer gives a resistance of about 6 ohms, but this is reduced to ~1.5 ohms in the plane that joins the winding to the wiper arm. This means that each winding is basically feeding a resistor network that limits the maximum "shorted turn" current to a harmless level. The resistor "network" also helps average the voltage between turns, so instead of voltage steps, the output is more or less continuously variable.


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## torch (Dec 8, 2014)

gunrunnerjohn said:


> I think you'll find the resistance to be MUCH higher going through the two rollers, the arms and hub contacts, and back to the rear terminals. It will be closer if you connect directly to the two arms, then you only have the roller to arm contact resistance.


Fair enough. Here we go:

First, I used some strips of tape to ensure that I had isolated one and only one winding, and there was no possibility that a roller could contact two windings simultaneously during the test (which would obviously skew the results):










Next, I followed your suggestion and connected alligator clip jumpers (#16 stranded copper wire, approx. 14" ea.) directly to the brass arms:












I positioned the rollers precisely on the exposed windings between the pieces of tape:











I verified contact by measuring the voltage from each test lead to ground using a Fluke 175. First the yellow lead:












Then the white. Note that the difference in voltage is just about what we both calculated it would be. (sorry about the shake on these two pictures, should have used the flash):











Using a Hioki 3102, I attempted to measure the current when shorting the yellow to the white. The needle barely moved on the 6 amp setting. So I took a third test lead and made 5 turns around the clamp to amplify the current: 











The amplified reading was as shown here:










I make that reading to be 2-1/4 amps, so the actual current through that wire is 2.25/5 = 0.45 amps. 

That could mean up to 12 watts at full power _if_ both throttles happen to be precisely aligned to short the same single winding simultaneously, a non-trival figure to be sure. But I submit that it is not likely to cause undue heating in a conductor capable of handling the current of a 140 watt secondary unless the transformer is being run for extended periods at near-full power with both throttles shorting the same winding. 

Also, while it may not be clear in the photos, it is worth noting that I have the earlier version of the KW transformer. I understand that there was a revised version starting about 1957 with a different coil body which can be identified by having riveted laminations. It is possible that the magnetic characteristics of the revised version are different and that the above findings are not applicable. 

Similarly, while the rollers are identical, the ZW coil is different plus the ZW potentially has 4 rollers that could short the same single winding. So the above experiment does not necessarily apply to that model either. 

As for the soldering gun example, I would assume that while the principle of operation is akin to shorting a secondary transformer winding, it is likely that the specifics of the design are optimized towards generating the desired current and heat. Conversely, Lionel made many, many transformers that using metal contacts that shorted at least 2 windings over the designed range of travel without harm, so obviously it can and has been done. I respectfully submit that the engineers adopted the same design philosophy with the KW (at least, the early version).


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## gunrunnerjohn (Nov 10, 2010)

No problem, it's not my transformer.


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## torch (Dec 8, 2014)

No, it's not. And I appreciate your taking the time to ensure I did not inadvertently damage mine. Thankyou. 

It would still be interesting to see how the end result compares to a graphite roller. Some day I may buy another KW so I can run more than 2 trains at a time. If I do, I will have to repeat the experiment with that for comparison.


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## servoguy (Jul 10, 2010)

I think a good test to run would be to have a roller shorting two turns and see if the winding is getting hot. Just see if you can touch it with your finger and not get burned. You don't need any load on the transformer to run this test.


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## torch (Dec 8, 2014)

servoguy said:


> I think a good test to run would be to have a roller shorting two turns and see if the winding is getting hot. Just see if you can touch it with your finger and not get burned. You don't need any load on the transformer to run this test.


I realize that the secondary voltage is limited to less than 20vac, so touching the windings should not result in any harm -- at least, no more harm than touching the track it powers. However, there is 120 vac floating around in there and they were not quite so mindful of safety back in the day, so I carefully avoided sticking my hands inside while the unit was powered. Maybe a laser thermometer or a temperature probe? 

Wandering off-topic (yet again, this thread is nothing like what I originally intended :laugh my then 7- or 8- year old son got second degree burns on his wrist by touching the live track way back when. His a Medic-Alert bracelet came in contact with both the centre and outside rails and heated up enough to burn his skin. It made me realize that the on-board breaker is just way too sluggish, and I added self-resetting breakers between the track and the transformer thereafter. 

However, you lose the pretty "overload" light function using external breakers (automotive 10 amp self-resetting type from Canadian Tire). Has anyone simply replaced the internal breaker? Is the breaker from the later revised KW design faster than the original?


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## servoguy (Jul 10, 2010)

This example shows the danger of wearing metal bracelets or jewelry around toy trains or car batteries. You can lose a finger in a hurry if a ring shorts across a car battery. The ring will become red hot almost instantly.


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## gunrunnerjohn (Nov 10, 2010)

None of the PW transformers had decent breakers. If you're really concerned about stuff like metal bracelets, I'd suggest a fast blowing fuse in line with the track feed.


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## torch (Dec 8, 2014)

Ok, maybe today's project will be somewhat less controversial. 

My 2-1/2 year old grandson managed to get ahold of an MPC passenger car and broke the plastic post that secures the plastic dummy coupler to the plastic frame. Go figure. 

Anyway, in place of the post, I turned a tee nut of the same OD to the required length and a flange-head 4-40 machine screw and now the Times Square rolls again:




























(and yes, I know I probably could have bought a replacement for this cheap snap-together model kit on eBay for less than the cost of heating the shop for the duration...)


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## rkenney (Aug 10, 2013)

torch said:


> (and yes, I know I probably could have bought a replacement for this cheap snap-together model kit on eBay for less than the cost of heating the shop for the duration...)


I like the way you did it much better! :appl:


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## gunrunnerjohn (Nov 10, 2010)

That fix will surely outlast the car!


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## Big Ed (Jun 16, 2009)

torch said:


> Several. From 1914 up to about mid-60's. I have mostly OMC, some Scott-Atwater and a couple of Mercs.


Cool, does it run?
You can hurt yourself with one of those the way they were made.
May I ask about how much one is worth?
Does it have an all brass lower end on it?

You have the decals that they came with on yours?


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## torch (Dec 8, 2014)

Does which one run? Most of my motors are runners. A few are parts motors and a couple are works in progress. For example, I have two 1961 Scott-Atwater 25E long shafts mounted on a boat that are fully operational and in regular use. In fact, that was the last boat out of the water this year. But they are like Sea King helicopters -- they need 10 hours of maintenance for every hour of use and 2 or 3 parts motors 'cause they haven't been made for over 50 years. 

Others are fully functional, but carefully drained of fluids and stored except for display or shows. The 1914 Evinrude is one of those. So is a nice little Johnson 4 on a wood display stand in the family room beside the couch. 

As for value, they are rather like toy trains: some eBay vendors think they are sitting on a gold mine. Some of mine were free from people who know I like to tinker and decide Grandad's old kicker that has been sitting under the cottage for the last 15 years needs a new home. Most come from other enthusiasts for a nominal fee at swap meets -- maybe $20 to $200, depending on make, model and year. 

I've flipped a few 60's and 70's 7.5 hp OMCs to people who want something for the kid's tin boat at the $200 range. They are quite popular as that is the largest size before you need registration numbers, are very reliable, and I can usually get them running quite nicely for about $100 in parts and some elbow grease.


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## Big Ed (Jun 16, 2009)

big ed said:


> Got any old Evinrudes?:smilie_daumenpos:


SEE ABOVE



torch said:


> Does which one run?
> 
> Others are fully functional, but carefully drained of fluids and stored except for display or shows. The 1914 Evinrude is one of those. So is a nice little Johnson 4 on a wood display stand in the family room beside the couch.


Evinrude.....1914...................................I am a Evinrude man.:smilie_daumenpos:
Maybe these are yours? ?


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## torch (Dec 8, 2014)

That second one sure smokes like mine ;-)

(I wish my steamers would smoke like that)


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## Big Ed (Jun 16, 2009)

I said brass lower ends, I see now that some had a bronze prop.

Cool, you display them.:smilie_daumenpos:
I think everyone should have at least one in their living room.:thumbsup:
There are some for sale I see, but some look like they been sitting under salt water for 60 years.hwell:


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