# reversing switch; DIY?



## Mark in Portugal (Jun 13, 2019)

hello; first post for me on this forum.


I'm American, live in Portugal, have some canal boats in Amsterdam [Netherlands].
As some of you may know, Amsterdam is going emissions free in a few years.


My service / work boat is 12-14 tons, 14 meters long, and 2.2 wide. If I want to keep it, I have to put in electric propulsion for use inside the town. 










It needs about 6HP to cruise [speed limit is very low]. 20 to stop would be nice but I;ll take what I can get.


This boat has a very low value; and so do I.



I had the opportunity to buy an old 12HP forklift motor from someone's go cart project, and a less old electronic control. It has no reverse contacts. 



















There are various challenges to overcome; right now I'm focusing on how to reverse.
It's a series wound motor with just 2 terminals; I will open it up and separate the armature from the field, and put in 2 more lugs.
I did this before, long ago, for a starter motor I re-purposed. 



Now I find there are no reverse relays rated at 150A 48V continuous. 

I found some single pole relays; but I'd need 4 of them, and they're too expensive.


So I'm considering fabricating a switch [I'm good at fabricating]. 

Has anyone here done this? how is this problem usually tackled?


----------



## Duncan (Dec 8, 2008)

Hi 
There ARE reversing contactors that will do nicely

http://www.albrightinternational.com/products/

Don't worry too much about the current capability - my small contactor from a 24v forklift lasted me for five years with 1200 amps going through it

I did kill it last year but a replacement - 36v unit cost me $110 from out local forklift scrappers 

The secret is to only shift directions at zero throttle

https://www.diyelectriccar.com/foru...dubious-device-44370p28.html?highlight=duncan


----------



## MattsAwesomeStuff (Aug 10, 2017)

Because you're a big, slow boat, not a car... I would not bother with switching contacts if your pilothouse is close to where the power cables run.

I would just build a Double-Pole-Double-Throw knife switch from scrap copper.










You can cover it if you want it to be pretty and not worry about a screwdriver falling across the contacts.

They make them in giant size too, which is just multiple pieces of thinner copper in parallel:










That one is 1600 amp! https://filnor.com/quality-products...ed-on-time/switches/type-l-knife-switch-back/

Probably like, $3 in scrap copper and a few nuts and bolts and a piece of wood to mount it on. $5 total.


----------



## Mark in Portugal (Jun 13, 2019)

Thanks for the replies;
Matt, I was thinking more like a spring loaded snap switch that operates with a marine gearbox push/pull cable.
But I'm interested if anyone has used any manual switch for this sort of application.



The boat is big and slow, but reverse is the brake on a boat. This thing will drift 100 yards after powering off, and the canals are full of shiny expensive vessels I don't want to pay for. The nose is a steel block!
No pilot house. 



Reverse is vital, and has to be quick and sure to engage. 



Duncan; 

thanks for the tip. 

I'd passed over a couple of albright relays that didn't suit, but now that I've had a better look I found many more; maybe there's one even I can pay for. 



But then I won't build my own, and I'll miss out on all the fun.


----------



## The_Sasquatch (Feb 11, 2018)

Mark in Portugal;1039465\ said:


> But then I won't build my own, and I'll miss out on all the fun.


Like Duncan said, you can use an inexpensive reversing contactor if you ensure there isn't any current flowing while the contactor switches... It sounds like the next thing you will need is a good throttle lever with a dead zone between forward and reverse that has a switch for energizing the reversing contactor... I'm not aware of a cheap off the shelf solution for that, and it sounds like a fun fabrication project.


----------



## Mark in Portugal (Jun 13, 2019)

The cheap ones look ok at first; then I realized that their ratings are reduced for higher voltages. 250A at 12v, 125A at 24v. etc. The contacts have a little resistance. 

I don't quite understand how a higher voltage should affect the switch; but now I'm spooked off of the Chinese cheapos on ebay.


The 'real' ones, albright for instance, don't lower their ratings at higher voltage.



The boat already has a morse single lever throttle / gear control for the diesel engine.
It has the required movement; gear lever moves, then the throttle. the throttle is closed before shifting to neutral or reverse.



I plan to add the rheostat to the throttle lever on the diesel [this is an OM636 Mercedes, and actually does have a throttle].
Then put limit switches on the marine gearbox lever to switch forward and reverse on the electric motor.
When one is off, the other will not respond.
The marine gearbox is hydraulic activated clutches, so when the engine isn't turning it will not engage, regardless of lever position.


Anyway, that's the easy part. 



The hard part is adding a water cooling jacket to the case.
The very hard is adding a water cooling jacket to the armature shaft [which likely won't happen].


----------



## Duncan (Dec 8, 2008)

Why do you want to go water cooling? - if it's a 12 hp motor and you only need 6 hp continuous then you are sweet!


----------



## Mark in Portugal (Jun 13, 2019)

There's a line on the plate that spooks me; "servizio s3 = 25%"
I don't know what s3 means, but I assume this meas duty cycle is 25%.




240 amps x 48V = 11.5 kw


The plate says the output is 8.3 kw 



so at full output, 3 kw has to go somewhere.


Maybe at 1/2 power it wouldn't melt; but it would be hot. then when I give it full power for 5 - 10 seconds, it would be too hot. 

With the fan cooling, slower motor speed means slower fan speed too.
I don't want to do all this work and have it running at the edge.



I have little experience with this sort of motor [I modified a starter motor for a reservable hoist long ago], so I'm open to suggestion. 



Here in Portugal I have a lot of time and a home machine shop. Once I ship the motor 2,500 km to Amsterdam and mount it into the boat, there's little chance of making any changes. When I'm there I have little time and only basic tools.


----------



## Duncan (Dec 8, 2008)

That motor - how heavy is it?

A very crude way of determining just how much power you can get out of it

A 9 inch diameter forklift motor is about 60 kg - that is about minimum size for a car

I'm using an 11 inch diameter motor - 105 kg 

I paid $200 for mine - it's continuously rated at 10 kW - but I'm feeding it 340 v and 1200 amps - just for a few seconds

I know you already have that motor but if it's not at least 60 kg I would be inclined to find out who repairs forklifts local to you and visit them with cash in hand to get a more useful sized motor

If it IS 60 kg+ then I would not worry too much - you can always add an external fan


----------



## Mark in Portugal (Jun 13, 2019)

It's around 7" diameter; I haven't weighed it but I guess it's around 40 kg.


There is no scrap anything in Portugal; finding this motor was almost a miracle. 

They sell things 90% worn out for 80% of the new list price. I've stopped wasting time even trying to find any used machinery here. And I'm in a rural area too.

So there will be no other motor. 


Sometimes I buy on ebay UK and have things shipped, but it's difficult to arrange transport for heavy items at a realistic cost. It's always different, but heavy items rarely work out.



I'll be shipping the rebuilt diesel back to Amsterdam in a month or two, and I can add the electric to the crate at no additional cost. 

It's only 100 euros if I have it correctly crated and I can load, so shipping from my home works out ok.


This is why it makes sense for me to do extra work now. A water cooling jacket isn't rocket science. 

Lengthening the armature shaft and adding a cooling chamber is maybe slightly rocketish...


----------



## Duncan (Dec 8, 2008)

Hi

OK so you will stick with that motor - the information on the nameplate - the voltage current and power

Series motors are funny things - for a fixed motor current the motor voltage is dependent on the speed 

So when it says 240 amps and 48 volts it will only do that at a specific rpm - which is where you missing 3 kW has gone - it's not heat!

When you get your motor in the boat measure the current - if you are using a controller it will control the voltage to achieve the demanded current

My motor is continuously rated at 208 amps - I suspect that you will need to stay below 200 amps for your cruising

I think a fan blowing down the inside of the motor will be of greater benefit than a water jacket - a water jacket will keep the iron mass cool - but it's not the problem - it's the coils that are NOT in contact with the iron that will overheat - and the Commutator


----------



## Mark in Portugal (Jun 13, 2019)

What you say about voltage and rpm is at odds with everything I've read, and my own first experiment.
I connected 32V [3 car batteries] and the motor did not run at the 2100 rpm on the info plate, but accelerated through 6000 RPM, when I cut the power.


Supposedly, series motors RPM is load dependent. no load = overspeed and destruction.



I agree with you about the heat in the armature being the tough part. 

There is already forced air though the motor; my reasoning is that if the field coils are cooler [cooled from the outside], the cooling air inside the case will have to be at a lower temperature than it would be otherwise.


The rear of the shaft has the heavy fan on it, which also acts as a radiator. I plan to add a water cooling chamber to the front of the shaft. Heat from the windings will bleed into the shaft, and out through the water [as well as being air cooled].

If I do it, I'll post the work in a new thread.


Happy news; I got a 400A Albright reversing relay on ebay for 25 GBP! 

View attachment 113109

OK, so it's a little rusty on the outside...


----------



## Duncan (Dec 8, 2008)

I will try and make it clearer

You are correct that a series motor will overspeed with no load - my point is that there is unique speed for each voltage and current combination

If the motor is doing 2000 rpm with 200 amps then it will need X volts from the controller

The 48 volt and 240 amps condition may be at a different speed that the speed on the nameplate so while the motor can take 48 volts and 240 amps that would require a different (higher speed) so would produce more mechanical power than the nameplate which is the power at the nameplate rpm

In a car like mine it goes roughly like this

Zero rpm - 1200 motor amps 20 motor volts ---- 340 battery volts - 70 battery amps - 24 kw

1000 rpm - 1200 motor amps 126 motor volts ---- 340 battery volts - 444 battery amps - 151.2 kw

2000 rpm - 1200 motor amps 232 motor volts ---- 340 battery volts - 820 battery amps - 278.4 kw

3000 rpm - 1200 motor amps 340 motor volts ---- 340 battery volts - 1200 battery amps - 408 kw

Then as the motor rpm keeps rising the current has to drop (controller is on 100%)

4000 rpm - 900 motor amps 340 motor volts ---- 340 battery volts - 900 battery amps - 306 kw


----------



## Mark in Portugal (Jun 13, 2019)

So I've got this albright reversing relay;









Supposedly it's 12V. 

There are no numbers on it at all, but there is the albright name. 



Now I wonder, is each coil 12v, or are they 6v each and supposed to be wired in series?
This relay is on/on, it has no central position. 

Coil resistance is too low to measure accurately, I'm getting 1 or 2 ohms.


I assume it's normally wired in parallel, 12V each, unless someone tells me Albright likes series wiring for dual coil relays.


----------



## Duncan (Dec 8, 2008)

Hi
Reversing contactors - you have two coils - call them A and B

Four possibilities

Both energised - NO DRIVE - no circuit for the motor
Both - off --------NO DRIVE - no circuit for the motor

A - ON and B - OFF - Forwards
A -OFF and B - OM - Reverse 

Forklifts use a complex switch/lever

I just have each coil through a switch - having to move two switches made my certifier happy - he was a bit worried about just a single switch to go from forwards to reverse 

The two "No Drive" positions give a "neutral" where an accidental push on the throttle won't do anything


----------



## Mark in Portugal (Jun 13, 2019)

Thanks for that, I understand now.


But another problem has emerged; the coils draw 3.5A; 40 watts. 

Albright catalog states that such coils are for intermittent use, lower wattage coils are for continuous use.


I wrote to Albright and asked if I could buy suitable coils but I'm not optimistic.


I could connect the relays to run forward with both coils off, and reverse with both coils on [which would be intermittent of course]. 

But then if one coil failed the field coil would be connected to 48V, not good.


----------



## Mark in Portugal (Jun 13, 2019)

I heard back from Albright; I can switch coils, they cost around 30 euros each.
The springs have to be changed for the weaker coils, they're cheap.
The new coils will be around 20w, and can be energized continuously.
Delivery in around 6 weeks they say.


----------

