Nirve Chopper Forks - A Complete System

[Knuckles]

Many moons ago ... on an ebay site Far Far away ... I found a brand new Nirve Tension Deviate Chopper for $189 + $49 shipping.


I snatched it up and it arrived at my door. I assembled it. I rode it around the neighborhood once. Then never rode it again but watched much dust settle upon it's once glistening frame! Yet those forks called to me! We want bats they cried! But a D cell was too big! And a C cell was a wee bit small. BUT ... an a123 was JUST RIGHT! And 12 fit perfect in each fork (86 cm fork length).

So the bike sat and sat and sat some more and I watched the ebay price of DeWalt packs rise from $80 to $90 to past $110! And I needed 24! (hey this kinda rhymes!)

But then I said WTF and bought 48 bats after much haggling with this guy I met on ebay (don’t tell ebay)!

Then crazydude sent me a 72V controller that fit (by God’s grace) perfect between the forks and a $1 plastic elec box from Home Depot fit between the forks too. And I cut my harness down to min length (24") and I ground out the fork tube (where the fender attaches there is a little metal tit inside the tubes) and I dropped those a123’s inside the forks (still a work in progress but many pics soon to come) and I now have everything for a FAST ride with no wiring (except for aux bats) beyond the neck (head tube) of the bicycle.

This freakin thing ...

 

[Dr. Shock]

How are the batteries connected inside the fork tubes? Do they just rest against each other like flashlight batteries, or did you solder connections?

How do you charge/balance the cells?

Are they easy to remove?

 

[ngocthach1130]

So the bike sat and sat and sat some more and I watched the ebay price of DeWalt packs rise from $80 to $90 to past $110! And I needed 24! (hey this kinda rhymes!)

But then I said WTF and bought 48 bats after much haggling with this guy I met on ebay (don’t tell ebay)!

Then crazydude sent me a 72V controller that fit (by God’s grace) perfect between the forks and a $1 plastic elec box from Home Depot fit between the forks too

Hmm since you like rhyme I'm going to rearrange this part of your story a bit. Need something to do while the body clear the caffeine from my system.

So the bike sat and sat some more
Slowly price of Dewalt soar
$80, $90, $104
I said Oh god please, no more

But then i said what the hey
i could buy a controller from on ebay
quick shipping is all i could say
Will this fit in the fork? It just may

 

[safe]

How are the batteries connected inside the fork tubes? Do they just rest against each other like flashlight batteries, or did you solder connections?

The new "craze" in battery pack design is "solderless packs" where the cells just press against each other.

One "secret".... you need to apply pressure with a SPRING and not a SCREW to keep the cells pressed together. This is because all cells expand and contract slightly when heated (and just outside temperature) and if you don't allow them to float they will loosen up.

The other "secret" is to use this (expensive) silver conductive paste that increases the conductivity between the cells to a level superior to soldering.

The only "problem" with the future of "solderless packs" is that there's no easy way to use a BMS and that means that your cells will be unmonitored on an individual level. It's because of that "gotcha" that it isn't the final destination of pack design. But for the here and now it's "good enough" and better than soldering.

Nice bike... I like the fork triple clamps... I'd love to get just the triple clamps at a reasonable price...

 

[RLT]

Neat Concept!

 

[Knuckles]

How are the batteries connected inside the fork tubes? Do they just rest against each other like flashlight batteries, or did you solder connections?

The new "craze" in battery pack design is "solderless packs" where the cells just press against each other.

One "secret".... you need to apply pressure with a SPRING and not a SCREW to keep the cells pressed together. This is because all cells expand and contract slightly when heated (and just outside temperature) and if you don't allow them to float they will loosen up.

The other "secret" is to use this (expensive) silver conductive paste that increases the conductivity between the cells to a level superior to soldering.

The only "problem" with the future of "solderless packs" is that there's no easy way to use a BMS and that means that your cells will be unmonitored on an individual level. It's because of that "gotcha" that it isn't the final destination of pack design. But for the here and now it's "good enough" and better than soldering.

Nice bike... I like the fork triple clamps... I'd love to get just the triple clamps at a reasonable price...

Bro you read my mind! bat pics commin' soon!

 

[Knuckles]

How are the batteries connected inside the fork tubes? Do they just rest against each other like flashlight batteries, or did you solder connections?

How do you charge/balance the cells?

Are they easy to remove?

Here are some photos to answer these questions ...
The fork tube comes with a hole at the bottom. I installed some grommets in these holes.

I used a 1-1/16" hole saw to ream out the metal where the fender attaches to the forks. The socket was dropped down the tube to check clearance for the bats.

The bats are not soldered. I put a washer (size of a penny) between each bat to ensure a good connection around the crimped bat insulator. The bat button is the negative terminal!

 

[Knuckles]

Then just tape the bats together into one long stick of 12 cells with a washer between each cell. The washer stays in position by the bat (paper) insulator.

 

[Knuckles]

Then drop the bats in to check for a good fit. These bats are in quite snugly with no room to spare. The positive terminals are up at the top of each fork.

 

[Knuckles]

Then I fabricated the stick end connectors using metal posts, springs and washers ...
posts at the end of eack stick (fork) with springs adding compression at the top of each fork. Added more grommets for insulation from the washers and fork tube metal.


And held the spring in compression by using a clip

 

[Knuckles]

The leads from each fork top and bottom were then inserted into the wiring box.

 

[Knuckles]

I added 30-amp automotive fuses for each + stick lead.

 

[Knuckles]

So there you go ... 24-a123 bats in the forks that can pop out for balancing when needed and 60-C NiMH bats in the back as aux power.

 

[Knuckles]

btw I charge each 12-cell a123 stick using a cheap crazydude 36V 2.5 amp SLA charger. I could probably use 4 chargers in p for each stick to rapid charge at 10 amps.

The chargers shut off (goes into float mode) when the a123 stick hits 44.6V. When the stick drops to 41.5V (many hours later) the charger will start up again.

Use same charger on the NiMH packs. A Klixon 50-C shuts off the charge circuit when the pack temp hits about 110-F (nice and warm bats). And the charger goes into float mode and will stay there until the NiMH pack drops to 41.5V and 100-F temp.

The a123 sticks and the NiMH packs co-exist in harmony together. One little happy family of WHrs.

bada bing!

 

[Knuckles]

Oh my Gosh. My bike just had a BABY!

Say hello to my little friend!

8-a123s going into each fork of Jr. He'll be 48V soon!

(and a nice hub motor for the yound lad waiting in the wings!)

 

[Dr. Shock]

Excellent work there, Knuckles. Truly an epiphany for the stealth fans.

 

[Knuckles]

Gosh! Thanks!

 

[Mr. Danelectric]

AMAZING! Where do I get a fork like that!?!?!? eBay, you say? I'm google hunting for them now! You ROCK!!!! Super Stealth!

Wait - are there any brakes for the fork? Looks like caliper mounting tabs for discs? I would need a front brake.