Friday, December 03, 2010

Absurdia Pt. 2: Black Cat Swingers

I have not had a lot of time to ride (nor warm weather, though the trails at lower elevations are amazingly still dry) so this post doesn't have much to do how my new singlespeed rides. Instead, it's about the dropouts - which I have gotten a ton of questions on.

If you're too lazy to read my ramblings in full, suffice to say that I think the Paragon sliders, as of now, are a better option. Here's why:

-The Black Cats aren't stainless. This is a pretty big deal to me, since you really need metal to metal contact to keep the dropout from slipping easily. Hence you've gotta leave at least some of the dropout unpainted - and that means (eventually) rust. A big deal to some folks, not such a big deal to others (here in CO, it's not an issue) but a serious downer on a dropout that costs $150/set (for reference, that's 50% more expensive than the Paragons, which aren't cheap).

I assume they're non-stainless to allow easy fillet brazing, but IMO this is a silly way to do things. Fillet pro would work fine if you want the fillet look, or these could be re-done as a plate/tab style dropout and they could be silvered in. Obviously for TIG guys/gals, an identical version in stainless would work fine.

-Set screws aren't integrated to the dropout. If you look closely at the picture, you'll see a small hole in the hood - that's where you're supposed to weld or braze an M4 eyelet to allow the set screws to be used. This is a PITA to do (I've heard of them popping off under load if brazed in, and if you TIG them like I did on my frame, you wreck the threads and have to do a bunch of work to re-tap).

-All the work is done by one bolt. The upper "pivot" bolt doesn't do much to keep the dropout from moving at the axle end due to the leverage involved, so really there is just one bolt (plus a set screw) on each side keeping your wheel in place. This has worked fine so far, but I worry that if that bolt came loose and wasn't noticed soon enough, the set screw would get bent/damaged and have to be extracted (giant pain). Again, the non-stainlessness of the dropout is a contributing issue, since the force needed to clamp the dropout in place is very high. That's a lot of torque on one (admittedly, big fat M8) bolt.

On my first two rides, the rear end of the bike came completely loose. I fixed this by using IRL-grade loctite on all the M8 bolts, and it's been fine ever since. So perhaps my concerns are unfounded.

-Finish quality is mediocre. They're ok, and it's not a big deal, but it's lame to have to bevel all the edges and corners yourself with a grinder or a file. It's not that hard or expensive to finish the piece nicely - especially given the price.

So far, my only complaint about actually riding with these dropouts is that they seem to correlate with incredible rear brake howling (yes, they're Avids, so it certainly could be the brake at fault, but the same brakes haven't had this problem for me on other similar bikes with different dropouts). I have heard from (trusted) fellow builder friends that under heavy braking, the wheel can move the brake side dropout *backwards* enough to cause problems, though this isn't something I've experienced.

However, they look cool, they have a nice range of adjustment, and they let me tension the chain - so far, they're doing their job.

With all that said, if I were building a new bike for myself today, I would go back to the Paragons. They are tested, reliable, and don't have any of the problems/issues that the Black Cats do - plus they're actually quite a bit cheaper and equivalent weight.

I'm happy to build with any dropout a customer wants, of course, and my whining here should be taken for what it is - niggling complaints about a very cool product. Black Cat should license the design or have some stainless models made, improve the finish quality, and incorporate a better set screw setup, and I'd be an even happier camper.


the mighty war-khan said...

Lovely write-up. It's good to see your constructive thoughts on these drops. I agree, they've a cool factor, and the idea of a single pivot is nice. Why they didn't go stainless @ 150 clams, who knows!

On a related note, if you ever see Julie & Julia, there's some dialogue about knives in regards to stainless steel. They don't mention high carbon steel, but what'd you expect from a chick flick cooking drama.

Julia wasn't pleased that knife manufacturers were moving towards stainless, which she considered inferior.

Anyways, your semi-nerdocity is much appreciated!

word verification: cutbre

joel said...

not stainless?, you sure?
whatare they made of then? I've not had a speck of rust on mine in 6 months and I'm running carbon steel deep socket M8 bolts that will rust w/o the linseed oil that I treat them with.

If you replace the bolt on the swinger that keeps the dropout in place with a stronger bolt, you can torque it down enuf that it won't move, even without locktite.

Anonymous said...

Great write up walt. Does Black Cat make a Rohloff OEM?

Walt said...

Joel -

Well, they certainly fail the magnet test (ie, low chromium content) and I know Todd fillet brazes (won't work with brass/stainless), so I'm assuming they are not stainless.

The bolts hold the dropout tightly enough (ie, you can torque them down just fine) - the issue is that they can loosen due to all the vibrations in the rear end. The loctite is on the threads, not the dropout.

Walt said...

AFAIK, no Rohloff version.

jkeiffer said...

Interesting. I like them over sliders because the rear triangle looks better. I have some Paragons now, and they have been fine for 2.5 years, but I still don't like the way they look and I wonder if the shorter CS's and ST's that are required might be robbing me of some compliance?

Too bad you won't do a pinch bolt EBB.

Walt said...

J -

I agree that the rear triangle looks nicer with these than with the Paragons. They also are mechanically a lot less hard on the chain/seat stay joints, which is a good thing.

I don't think there's probably any compliance difference. On mountain bikes, the effect of the tire pressure is going to be way, way more important than anything involving the frame.

sluggish said...

In Julia Child's defense, nobody figured out how to make a decent chef's knife from stainless until the late eighties. All the early stuff from the sixties and seventies is worthless--in those days you were a lot better off with high carbon steel.

I've been very happy with the Paragons on my bike. Another small advantage of the Paragons is that the slider is keyed into the slot in the dropout, giving you more engagement with the clamp bolts. The key also prevents the tension screws from seeing any side loads, which is nice.

Paragon has started making flanged ones, too, for nice stay junctions. The price on those is well into nosebleed territory, though.

blackcatbicycles said...

Hey Walt,
Someone hipped me to your critique of my dropouts. Thanks for the feedback. You have some valid points, I’ll see if I can convey to you and your readers the thinking behind the part.
The dropouts are not stainless, they are machined from 5/8” billet 4130 cromoly steel. There are a few reasons why:
Economy. 17/4 stainless, the only stainless worth dealing with for this application, is about the same price as 4130 and is about double the price of 4130 to machine. 17/4 is harder so it takes a long time on the tools. Other stainless will end up having a divot where the clamp bolt does its job on the slot and then you’ll have a hard time adjusting out of that one spot. No good.
Mild steel would also get a divot. It would cheapen the dropouts by about $50 and no one would know until it was too late, so 4130 is the right choice. Most other dropouts if not stainless are mild steel, Paragon included. Not shit talking—for a vertical dropout, it is a great choice.
With 4130, the dropouts are lighter. Having a stronger material allows less material.
I have a batch of very expensive 17/4 dropouts. Right up there with the flanged
Paragons. Fillet brazers can use 50-n for the same effect. Metal to metal contact is not necessary. After the first ride or two, things don’t move around much using powder or wet paint. Probably what you have experienced. I live about ½ mile from the largest body of salt water in the world, in a place renowned for fog (even locally), and don’t have a rust problem on the dropouts. This is a place where 317 stainless steel turns to powder. You can come look at the barrel adjusters on my townie.
Why flanges? Wouldn’t it be cheaper to make them out of plates to silver braze in slotted stays? In a word, “yep.” But, I like flanges. Makes the dropout stiffer in all the right ways without the additional weight from additional thickness. Since I’m the one making the dropouts, I get to call the shots. Moreover I can use a smaller diameter tube with a thinner wall thickness on stays when I use my dropout, since they stiffen things up so nicely. A down side to that? Can’t think of one. The flanges are blocky because they are made for a 500 pound gorilla. If you’re not one, the builder can carve them up to match your aesthetics or body weight. The dropouts are tumbled to remove any burrs. Sorry if your pair didn’t see enough time in the tumbler. If the bevel wasn’t what you like, it may have been perfect for someone else.

blackcatbicycles said...

Me again,
Set screws (m5, by the way): I get a lot of questions about that. I’ve put an enormous amount of thought into not integrating them.
Economy. One side of the dropout is machined, then a guy with a wrench comes and flips it and the other side is machined. If the guy had to turn it a second time, more money. If the machine had another axis with which to work, it is a more valuable machine, more money. You want 17/4 dropouts with an integrated set screw? Do you have some capital for a batch of 25 pair?
The bosses are easily replaceable should one get stripped: heat it up a bit, pop it off, pop on a new one. If they are sheering from shear (ha!) burlyness (yeah, right) they’re not brazed on well. Hope those people with this trouble you’ve heard from aren’t doing lugs.
I’ve more or less addressed the price thing, but one more point: I’m paying local bike people for their time and experience. It’s not as cheap as someone from Taiwan, or Michigan for that matter. But I like to have bike people around me doing what they love: Making bike things for other bike people. If my customers can drop $50 into that bucket (I don’t make much money on these things, for sure) out of the $3000 they will spend on a new bike, then God bless ‘em.
Lastly, (I’m sure ya’ll are stoked) can’t help you with the howling. I’ve ridden mine, with and without Avids, for 6 years without a howl. Never heard of anyone else with that problem, maybe they’re just not saying… I do always check the alignment of the face of the dropouts when checking alignment of rest of the bike.
Hope I’ve shed a bit of light from this dim bulb.

Walt said...

Hey Todd -

Thanks for chiming in! The brake howl is probably the brake - the Avids are notorious for it, and perhaps they just got to the point in their lives when they decided to complain. I haven't make any effort to fix that yet, I'll update everyone on the results.

It might be worth talking to Mark about making these - he seems to be able to turn out a more complicated product (ie, the sliders) for significantly cheaper. I bet you could get him to make a 17-4 version and you'd be surprised how inexpensive it would be - all while keeping your money in the US.

Any tips on keeping the driveside swinger from moving? It gradually seems to creep forward (no matter how tight I get everything) on just about every ride.

BTW, contact me if you want to pursue doing a big batch and need some capital to make it happen.

G Funk Ooley said...

I've been hammering my Black Cat for 4-5 months now here in Durango. For what it's worth, my swingers haven't budged one bit even though I have switched cogs and chainrings and thus adjusted them a half dozen times. Plenty of opportunity for me to get it wrong, forget to tighten one of the M8s, etc. So far, they've been bomber. I ride fully rigid SS and love keeping up with full-suspension friends on DH and technical trails, and I'm 195 lbs. My experience so far has been that the swinger dropouts are bombproof.

Walt said...

Always good to hear more feedback, but I have stopped using these after experiencing the dreaded *rearward* wheel slip under hard braking a couple of times. Not fun to have your rear wheel lock to the frame around a chundery berm, and once you're worrying about that happening, you're not the same rider.

So it's Paragon for me and my bikes.

G Funk Ooley said...

Fair enough. Maybe I need to increase my braking force. Or decrease my bolt-tightening force.