Hardened #25 Chain

Technical Technical Discussion
1

So on Team 1310 this past year we used standard #25 chain and experienced a handful of breakages, we’ve heard of teams like 118 using hardened #25 chain (I believe it’s called #25R or similar).

Does anyone know where we would be able to get some? Any retailers in Canada?

Thanks all!

2

Maybe your thinking of Heavy Duty 25 Roller Chain? Does Canada have Amazon? (seriously, I don’t know)

3

The chain 118 uses is #25H roller chain made by Diamond Chain Company.

4

VEX also offers #25H chain now.

5

we use this 25H chain i think Product | Designatronics Store | Stock Drive Products/Sterling Instrument that or the aforementioned diamond chain but i think we have other random stuff maybe vex? i dont really know
and we have never had problems. Just know that these still do stretch so you need to do the math to pre-load them (which is what we do)or have tensioners.

here are the calculators/references we use for chain length/pre-load
http://www.botlanta.org/converters/dale-calc/sprocket.html

what ever you do please just try to stay away from half links as these will alway be the weakest link in the chain

6

The 25HD chain is physically thicker and heavier than regular #25. If you use master links (which I don’t recommend) you’ll want to also get 25HD masters. If you use a chain splicer such as the Dark Soul tool, it’s made for #25. It is possible to use it on #25 chain (though making the first break requires a bit of torque as you dimple the die), but then it will never work right on regular #25 without a lot of futzing. (I’m not sure about the Vex or other splicers.) If you make the switch, go all the way with it or at least make sure you keep the two weights and their accessories/tools separate.

7

We have always used the 25 that vex sold which till recently was just normal 25.

8

As far as i can tell vex has only started selling regular 25 chain recently (i think since the ftc release) and the #25H chain they have been selling for a while now.

9

VEX originally sold #25H chain. There was an issue found in late 2017/early 2018 where our supplier had shipped us #25 instead of #25H. Unfortunately we didn’t have the time to get more #25H chain before the end of build season. Instead, we sold it as #25 chain.

Obviously there are teams in FRC that prefer to use #25H and some that prefer to use #25. To accommodate both groups we decided to keep selling the #25 chain as 217-2775 then in August we started selling #25H chain under a new part number (217-6439).

#25H chain works with #25 sprockets. The major difference is that the plates of the chain are thicker. This means that it’s not only stronger (209 lbs vs. 154 lbs working load), but heavier (0.108 Lbs/ft vs. 0.087 Lbs/ft).

The thicker plates means that you may need more space between sprockets to accommodate the wider chain. In addition, the master/half links for #25 and #25H chain are not compatible with each other.

TLDR: If you bought #25 chain from VEX prior to January 2018 you actually bought #25H chain.

10

EDIT: Jon Jack with the truth bombs.

EDIT2:

This should probasbly be spelled out somewhere in text on the VEXpro website for 217-2775, not just posted on CD.