Source of Belleville washers for 300kgf fixture?

fafrd

Solar Addict
Figured this subject was most appropriate in the LiFePO4 Forum since it’s only that technology that seems to benefit from ‘fixtures’.

After first seeing reference to ‘Belleville Washers’ in this Forum, I’ve now come up to speed on what they can do, and they are an elegant solution to solving the ‘12psi problem’

Having started to look for sources, what I’ve discovered is that the Belleville Washers that are fully specified including Spring Rating (‘ at flat’ or ‘lbs F 100%’) are expensive:

while the cheapo washers on eBay or Amazon don’t come with any Spring Rating.

I know several members here on the Forum are planning to use Belleville Springs in their fixtures and I’m wondering whether there are any members who have found good sources they can share.

And I suppose there’s no dedicated thread to designing a 300kgf fixture with Belleville washers, it would be great if any posters could also summarize their plan and/or how their fixtures worked out...
 

Bob B

Photon Sorcerer
These are very interesting.... but expensive.

Maybe we could do some sort of group buy. Problem with that is that it is going to be a major pain for someone to buy and re-distribute.
We would have to decide which one would be the most universal ..... for the 5/16 with the least force (part # 312-023-625). These have 78 lb force each.... maybe 3 or so in series could be used.
But .... they cost $7.25 each .... if you buy 1000, they are only $.73 each. That would be possible if we could get say 20 people who would commit to 50 each .... but a standard size would have to be agreed upon.

 

fafrd

Solar Addict
These are very interesting.... but expensive.

Maybe we could do some sort of group buy. Problem with that is that it is going to be a major pain for someone to buy and re-distribute.
We would have to decide which one would be the most universal ..... for the 5/16 with the least force (part # 312-023-625). These have 78 lb force each.... maybe 3 or so in series could be used.
But .... they cost $7.25 each .... if you buy 1000, they are only $.73 each. That would be possible if we could get say 20 people who would commit to 50 each .... but a standard size would have to be agreed upon.

That’s one option. Another option is for someone to bite the bullet and characterize one of the cheaper offerings.

These are only $13/100 but I spoke to the company and they stated they are ‘unrated’

Anything in the 25-75 lbs range should work. And also, depending on cost, it may be easier/cheaper to go with 6 or even 8 rods using lighter-rated washers.

What you want to avoid is washers rated under 10 lbs or over 200lbs - you need a total of 165/lbs x #cells x (1mm / max_displacement) washers per rod (so 100 washers really may not be too many).

Washers with ~1mm deflection (max_displacement) translate to needing about 1 per cell per rod, so 32 washers for an 8S battery with 8 rods if they are 165 lbs each, or 64 washers if they are 80 lbs each, or 96 washers if they are 55lbs each.

Those ‘unrated’ washers I linked to are also cheaper by the 1000, but for a savings of $0.03 per washer, the whole group buy thing is hardly worth the headache.
 

Bob B

Photon Sorcerer
More like $0.57 / washer .... and the ones I linked are $1.33 / washer .... $133 / 100 washers, not $13.30 ..... but you are right, a group buy would be a major hassle.
 

fafrd

Solar Addict
More like $0.57 / washer .... and the ones I linked are $1.33 / washer .... $133 / 100 washers, not $13.30 ..... but you are right, a group buy would be a major hassle.
For the #8 SKU #111202-012 I see $13 for 100 ($0.13 each) or $100 for 1000 ($0.10 each). What am I missing?
 

Bob B

Photon Sorcerer
For the #8 SKU #111202-012 I see $13 for 100 ($0.13 each) or $100 for 1000 ($0.10 each). What am I missing?
I guess we are talking about 2 different springs ..... I was talking about the 1 I posted a link to earlier.

Could you post a link to the one you are referencing .... I'm not finding it in the catalog that you posted a link to.
 

Bob B

Photon Sorcerer
I don't see the force specifications for that one .... but I'm not sure I would want to go smaller than 1/4 or 5/16 for the threaded rod. Their 5/16 is till only $19 / 100, but don't see force spec.
 

fafrd

Solar Addict
I don't see the force specifications for that one .... but I'm not sure I would want to go smaller than 1/4 or 5/16 for the threaded rod. Their 5/16 is till only $19 / 100, but don't see force spec.
That’s the point I’ve been trying to make - the ones including force specifications are much pricier...

These relatively ‘budget’ ones don’t have force specifications (and the supplier told me the force is ‘unspecified’), but at least they should be relatively consistent.

The ultra-cheap ones on Amazon and eBay are a total crap shoot (get them while they last).
 

Factory400

Solar Addict
McMaster Carr

Wave Springs are also very interesting:
 

Bob B

Photon Sorcerer
Ahhh .... they are much more affordable on McMaster-Carr. A package of 12 of the smallest force 5/16 one is $6.63 and is 70lb. Still not cheap, but if only using 4 rods, 1 package might be enough.
 

fafrd

Solar Addict
McMaster Carr

Wave Springs are also very interesting:
I thought I’d checked them, but apparently not...

That’s probably the best deal yet I’ve seen on calibrated washers, but still significantly more than the ‘unrated’ washers.

For example, the 5/16” 110-159 lbs washer is close to perfect, but at $3.36 for 3, that’s $1.12 each.

But with 0.762mm (0.03”) deflection, you’ll need 8 per rod or a minimum of 32.

But $36 per 8S 280Ah battery is a good starting point...
 

fafrd

Solar Addict
Ahhh .... they are much more affordable on McMaster-Carr. A package of 12 of the smallest force 5/16 one is $6.63 and is 70lb. Still not cheap, but if only using 4 rods, 1 package might be enough.
At 70lbs you’ll need two in series (for 140lbs). I didn’t check deflection but suppose you’ll need at least 8 stacks to get 1/4” of total deflection. So 16 washers per stack or 64 total.

6 packs @ $6.63 comes to just under $40, a share higher than the 150lb option I considered above (and assuming identical deflection).

64 or even 96 washers at $0.13 each is 1/3 of these rated options, so I’m thinking I might give them a try first...
 

Bob B

Photon Sorcerer
At 70lbs you’ll need two in series (for 140lbs). I didn’t check deflection but suppose you’ll need at least 8 stacks to get 1/4” of total deflection. So 16 washers per stack or 64 total.

6 packs @ $6.63 comes to just under $40, a share higher than the 150lb option I considered above (and assuming identical deflection).

64 or even 96 washers at $0.13 each is 1/3 of these rated options, so I’m thinking I might give them a try first...
I think the rating of 70 lb is at full deflection .... I don't understand your reference to 1/4 deflection. If using these, i would probably do a full charge and then go to nearly full deflection. Is there a specification for what the force would be at 1/4 deflection?
 

HaldorEE

Photon Sorcerer
I thought I’d checked them, but apparently not...

That’s probably the best deal yet I’ve seen on calibrated washers, but still significantly more than the ‘unrated’ washers.

For example, the 5/16” 110-159 lbs washer is close to perfect, but at $3.36 for 3, that’s $1.12 each.

But with 0.762mm (0.03”) deflection, you’ll need 8 per rod or a minimum of 32.

But $36 per 8S 280Ah battery is a good starting point...
My vendor chimped out on me. Ordering a variety of these from McMaster Carr in 5/16" (the diameter of my threaded rod).

Thanks for the direction.
 

fafrd

Solar Addict
I think the rating of 70 lb is at full deflection .... I don't understand your reference to 1/4 deflection. If using these, i would probably do a full charge and then go to nearly full deflection. Is there a specification for what the force would be at 1/4 deflection?
Whoops. Forgot the “ symbol (inch).

If you assume each cell swells by 0.75mm to 1mm, you need 6-8mm of range for an 8S battery (ie: 1/4”)

Since the largest deflection range I’ve seen on these washers so far is ~0.75mm, that translates to 8-10 washers stacked in series per each threaded rod..,
 

HaldorEE

Photon Sorcerer
Whoops. Forgot the “ symbol (inch).

If you assume each cell swells by 0.75mm to 1mm, you need 6-8mm of range for an 8S battery (ie: 1/4”)

Since the largest deflection range I’ve seen on these washers so far is ~0.75mm, that translates to 8-10 washers stacked in series per each threaded rod..,
Good reason to do two stacks of 4.
 

fafrd

Solar Addict
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