# Main fuse holder material



## evmetro (Apr 9, 2012)

I have a couple scraps of polyethylene starboard and was wondering if this stuff is ok to make a fuse holder for my a30qs500-4 shawmut fuse with. If not, what is the best plastic to use?


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## racunniff (Jan 14, 2009)

evmetro said:


> I have a couple scraps of polyethylene starboard and was wondering if this stuff is ok to make a fuse holder for my a30qs500-4 shawmut fuse with. If not, what is the best plastic to use?


Best to get a dedicated fuse holder. HDPE is "OK" as an insulator - but it melts and catches fire. Not what you want in a fuse holder, in my opinion. There are Ferraz-Shawmut holders spec'd for the fuse you list - will run you probably in the $50 range. Compared with how much $ you probably already have in your EV, this is very cheap.

Another option would be to build one from glastic insulating standoffs, like Mar-Bal 16032 or equivalent. This will be cheaper but you'll need to be careful to appropriately torque the standoffs to their support.


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## evmetro (Apr 9, 2012)

I went ahead and used the polyethylene. If there is ever enough heat to ignite this stuff, I will probably be exiting the vehicle and running away...










I put a drain hole on the bottom plate










Here it is.


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## davidmillin (Dec 14, 2013)

I like the look of that are you glueing the two pieces together or relying on the mounting bolts and screws to hold it together?


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## twright (Aug 20, 2013)

$50 is outrageous for that insulator. Give these people a call: http://www.standardradioelec.com/P266C-691?utm_source=oemsTrade&utm_medium=buyNow

They have to be cheaper than $50.


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## evmetro (Apr 9, 2012)

davidmillin said:


> I like the look of that are you glueing the two pieces together or relying on the mounting bolts and screws to hold it together?


The bottom plate is only held on when I use those 4 mounting holes near the corners. I picked up the the sraps at Tap Plastics in their scrap bin. The 1" 8x8 square was 1 dollar, the thinner scrap was 50 cents for an 8x8 square. They told me that you can't glue this stuff.


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## evmetro (Apr 9, 2012)

I made sure to drill the stud holes in the widest possible position so that it is easier to fit the large 0/2 cable lugs on it.


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## evmetro (Apr 9, 2012)

twright said:


> $50 is outrageous for that insulator.


I bought the shawmut version of this for 50 something dollars for my first build, and it looks like it should cost less than $5 at harbor freight. I am glad to see that I am not the only one who thinks that 50 bucks + is outrageous.


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## davidmillin (Dec 14, 2013)

> The 1" 8x8 square was 1 dollar, the thinner scrap was 50 cents for an 8x8 square.


Fantastic I love this sort of resourcefulness. Did you consider using a second nut and washer below the fuse so you can torque your connections nice and tight?


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## major (Apr 4, 2008)

You're not relying on compressed plastic for the electrical connection, are you? If so, it will fail. Compress the mating contact surfaces using metal fasteners only.


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## evmetro (Apr 9, 2012)

major said:


> You're not relying on compressed plastic for the electrical connection, are you? If so, it will fail. Compress the mating contact surfaces using metal fasteners only.


I thought about installing a pair of metal sleeves in the block, but figure the double nut would do the trick.


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## major (Apr 4, 2008)

evmetro said:


> I thought about installing a pair of metal sleeves in the block, but figure the double nut would do the trick.


Use a nut on top and bottom of the cable lug and fuse tab joint with heavy steel washers and lock washer(s). Do not use nylon insert lock nuts. And use nothing in between the cable lug and fuse tab. Keep the high current contact mating surfaces in direct contact with each other compressed at full recommended tightening torque for the threaded fastener used. Wrench on bottom nut and torque wrench on top nut.

Just use the plastic to hold the whole assembly in place and insulate it.

The only time I've seen an EV burn to the ground it was due to loose fuse connections. Ironic that the protection device caused the demise. But that's what happens when it is done wrong.


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## evmetro (Apr 9, 2012)

major said:


> Use a nut on top and bottom of the cable lug and fuse tab joint with heavy steel washers and lock washer(s). Do not use nylon insert lock nuts. And use nothing in between the cable lug and fuse tab. Keep the high current contact mating surfaces in direct contact with each other compressed at full recommended tightening torque for the threaded fastener used. Wrench on bottom nut and torque wrench on top nut.
> 
> Just use the plastic to hold the whole assembly in place and insulate it.
> 
> The only time I've seen an EV burn to the ground it was due to loose fuse connections. Ironic that the protection device caused the demise. But that's what happens when it is done wrong.


Major, I really appreciate your input on this, and I will follow these connection recommendations. I am not sure if it makes a huge difference or not, but I paid a little more to get all stainless steel hardware. I will go back and get the stainless lock washers. If it makes a big difference, I can cut some metal tube and sleeve the bolt holes...


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## major (Apr 4, 2008)

evmetro said:


> Major, I really appreciate your input on this, and I will follow these connection recommendations. I am not sure if it makes a huge difference or not, but I paid a little more to get all stainless steel hardware. I will go back and get the stainless lock washers. If it makes a big difference, I can cut some metal tube and sleeve the bolt holes...


I don't like SS hardware. But that is just a personal thing. I know of no reason not to use it. But me, I'd go with grade 5 or better, plated. I don't see why you want tube sleeves on the bolts. Use a nut to fasten the bolt to the plastic and then 2 nuts to clamp the electrical contact. Are you going to be able to put a wench on the bolt head when the holder assembly is installed and you go to fasten down the cable? And you want to periodically re-torque those top nuts, so need to put a wrench on the bottom nut. This should be similar to torquing nuts on the motor terminals, right?

Like shown on the attached photo.


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## evmetro (Apr 9, 2012)

I can use the three nuts like that holder in the pic, but if I can get it down to just two it will look a bit cleaner. I am really into both form and function, so if I were to use a metal sleeve then I could squeeze it between the bolt head and the first nut. You are quite right that the bolt head hard to get a wrench on, but I have that bottom plate drilled big enough to put a socket on. It is actually drilled to the diameter of the washer, but a 1/4" drive socket fits it with no room left over.


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## major (Apr 4, 2008)

evmetro said:


> I can use the three nuts like that holder in the pic, but if I can get it down to just two it will look a bit cleaner. I am really into both form and function, so if I were to use a metal sleeve then I could squeeze it between the bolt head and the first nut. You are quite right that the bolt head hard to get a wrench on, but I have that bottom plate drilled big enough to put a socket on. It is actually drilled to the diameter of the washer, but a 1/4" drive socket fits it with no room left over.


Whatever works for you to be able to get that connection secure. And don't forget, that bolt/screw/wrench can be live. You don't want to be sticking metal tools into hard-to-reach holes. Sure, you want it to look good, but be safe.


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## Frank (Dec 6, 2008)

I did something similar with electrical grade f-glass but also used epoxy to seal the bolt heads. Like major said: grade 5 hardware with nuts, washers, etc. on both sides of the connection.


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## evmetro (Apr 9, 2012)

Anybody know if regular fiberglass polyester resin and cloth is ok to use as an insulator? Nothing sticks to this polyethylene, so it would be pretty easy to make a mold of this so I could make more of them for my other projects.


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## evmetro (Apr 9, 2012)

Just in case somebody else builds this, I went ahead and sleeved the bolt holes so that the fuse does not need to be double nutted. The sleeve is a few thousandths short so that the washers on the top and bottom can still have a tiny bit of pressure on the plastic.


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## Nabla_Operator (Aug 5, 2011)

*Re: Main fuse holder material (SS)*



major said:


> I don't like SS hardware. But that is just a personal thing. I know of no reason not to use it. ...


Stainless Steel Fasteners relax after a while. Not so fast as plastic screws, but SS not desired where heavy loaded, vibrating, safety parts are mounted together. Highly pretensed bolted connections are likely to be made with Zinc plated Steel screws, instead of SS. Or with Titanium.
I was looking up internet hyperlinks for you, but cant' find them so easily, so it is not so widely known outside the high-tech + aerosp. industry.

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