Coal Bicycles' 84 is a 170mm Travel, Steel, Dual Link Frame - Bespoked Show 2021

 Agreed, butt welds = disaster waiting to happen

 it's true but it's both steel and full suspension, it'll be fine

 @baca262: that's not how that works

 I'd tend to agree, even tho this comes with a lot of eyeballing and no further details about that connection or even a FEA. It just looks like a bad idea, period. But we need to keep in mind this is a WIP prototype.

For those dismissing the stress around that area, bear in mind that even V1 Raw Madonnas were failing there (the XLs I think)

 I might be wrong - but I thought Reynolds 853 hardened around the weld and increases its strength. One of the benefits of this tubing. I really like this bike. Good job

 @jimbobley: it just transfers the issue to the area next to the weld

 @Arierep: What do you mean about an issue? The strength will be the same as the rest of the steel tubes, it depends how thick they are.

 @jimbobley: ok, let me correct, the potential issue. And, if the weld increases the substrate strength, by default you will have a difference in strength along the tube, which leads to stress concentration

 @Arierep: i'd venture guess the whole frame was heat treated because of the gussets at the headtube so it should be fine

edit: just googled it, that's not how it's done. but still, the extra material at the weld should make it limited by the strenght of the tube, if the tube's thick enough it'll live

 @baca262: even if we disregard the existence of the weld, that geometric shape with the sudden angle and edge is just objectively bad structurally. Any edge is a stress concentration point, that's undergrad engineering 101. Go check any motorsports rollcage handbook and they're quite specific about it.

Even if we had an hypothetical tube with No weld but that shape, it would still be sub optimal.

Again, I need to be careful with me comments here, as this is a prototype. I don't want to bash these guys needlessly over some make do part they already know it's not feasible for production

 @Arierep: That type of miter joint can work better if a disc is welded in between the joint to help the torsional load, hard to say if Coal did that or not.

 @baca262: you’re clearly out of your element Donny. Gussets don’t signal heat treating in any application. Sure “it’ll live” under most riders, but the heavy hitters will always figure out a way.

 Try bending 853...it won't end well!

I agree though; it's not a pleasant solution.

 A butt weld can work (I have done a good 50 downtubes this way for various reasons over the years), but I always gusset them when I have to do that. Otherwise, yeah, super sketch.

-Walt

 @jimbobley: The problem is fatigue. No matter how hard/strong the weld is, there's a big geometrical defect on both toesof the weld bead, plus the residual stresses that will compensate for the higher strength. At best, that weld will have a maximum allowable load of 71 MPa at 2 million cycles, as there's no way of controlling the quality at the root.

 @baca262: Assuming wasn’t the mistake. The mistake was ignoring that little voice in your head saying “you’re talking out of your ass here” and then closing with “it should be fine” while discussing the area of a bike most likely to cause serious injury in a failure.

Also: a few downvotes and a dismissive comment is not getting “shat all over”.

 @trainboy17: Butt welds provide several advantages, including: High strength with complete fusion, Easy to machine, Distortion control, Easy to inspect - all done by someone with over two decades of experience. And, it's steel.

 @Arierep: I've just used Ariereps' post as a starting point, with regards to the butt weld issue.

853 is a great material. I first used it in the mid / late 90s (well, whenever it first became available here in OZ), and, despite my concerns as to it being, perhaps, too hard / brittle from it's pronounced air maraging properties, I've never had a failure with regards to weld / HAZE zones. It IS a bastard of a material to ream out seat tubes and face and ream head tubes, , both before and (bloody hell) after welding.........

Perhaps the maker / designer wants the 'dog leg' butt joint to be a feature of their frame?

Each to his own - I dislike such features.

You've the travel of the reservoir during compression, PLUS, the lowering of the Whole shock to deal with. There are a few shocks with far longer / further from the body eye / trunion center line, that they may be trying to account for, too.

Though, on just basic eyeballing and line drawing over a printed picture, I think there is enough clearance for that joint to be further towards the BB area. A friend just said to me perhaps the butt joint is positioned to allow fitment of the 853 sticker - she's a cynical individual.

But, I'd never have such a joint, at such a point (but, I also have No bent tubes on my Suspension frames) . If it HAS to be there, for the previously mentioned Reservoir clearance issues, it would be wise to extend the lower link mount plates to go Across the Butt joint. The designer has the right idea with his welding those existing plates on the neutral axis - just bring them up to cross the butt joint. Lightening holes, with spaced fish mouth cut outs, would keep weight down, while looking 'nice'. That would be far better than say, a 'saddle gusset, with welds on the neutral (outside of the DT) axis only, which is another way to reinforce a butt joint.

Tiny saddle gussets on the headtube to TT and DT, on a 170mm travel bike, that some owners may be going Very hard on, seems a bit inadequate to me (Especially if they are too close to internal tube butting). And the relatively small diameter tubing is of concern - but, you are limited with 853 sizes.

But, I Do tend to build DH frames that are 'somewhat' Hefty....... I just weighed the swingarm that is going on a Pinion DH frame, and it's heavier than many whole Trail frames. Done that heavy, to later, put on my personal E Bike (when / if ever, I make it) . I'll be using lighter gauge and far less materials to make a lighter swingarm for the Pinion frame, when some steel gets to me. Ah, the joys of C19 delays. I'm not talking ounces here, I'm talking pounds / kilos.........

 @Bearorso: I like your friend

 @Arierep:

I Love Her!

She's definitely my better half, keeps my Grumpy Old Bastard side in check. Well, just a little........

 Maybe not .If you bought a high end cromo hardtail off the west coast of canada back in the day ,there where only a handful of guys actually welding them. subbing out work to the guys who are masters of the trade is cheaper then trying to train and tool . paul brodie chris dekerf

 @mxmtb: Lot of truth to that. On the US east coast, a majority was sent through BREW for the labor

 he meant stanton you div

 @Compositepro: i believe he's done contract work for other brands too.

 @AidanWilson: yep

 You done a Ribble?

 @blowmyfuse: Steve Garn from BREW and don't forget Frank The Welder (FTW) for east coast. He has worked for endless companies full-time and contract

 @mxmtb: and Mike Trulove

 @bman33: FTW was west coast until about 15 years ago.

 @mxmtb: got a truelove painted by dekerf sitting in the other room!

 @BikesBoatsNJeeps: true, but he did a great deal of work in the North East back in the mid 90's

 @vinay: no idea why you got down voted so much? You got a hater cult following you around PB?

 @blowmyfuse: North american susceptibility probably.

 @bman33: Frank the Welder. Now that's a name I haven't heard in a long time. Buddy of mine had a steel hardtail that was supposedly built by him. Probably 15 years ago. Had an absolutely jaw dropping powdercoat. Dark bronze with copper flake.

 @z-man: youtu.be/pi90F7mZUAM

To some of us this is how bikes are suppose to look!

 The steel Starling Murmur is just under 8 pounds for the large size, I bet this isn't too much more. The half steel Cotic Rocetmax is about the same. Both of those are lighter than Transitions new aluminum frames, so I bet this is no more than them.

 @z-man: 100% subjective. Some like that look, some don't. Neither effect performance

 @bman33: yeah but as an CNC programmer this looks just not done. Same for most frames. I like the sleek look way more.

 @Serpentras: what’s the time difference?

 @z-man: wtf is a ‘rotor mark’?

@Serpentras: As a CNC programmer I’m sure you understand your job is to make a part to spec, including price and aesthetic?

Personally, I love the machined look, I also pay the monthly finance on a few machines so from that perspective would rather not watch my spindles running flat out surfacing for no benefit what so ever.

It seems like it’s a funny ‘in joke’ for machinists to hate on machining marks, not that it’s done hope any harm….

 @Serpentras: as I mentioned, it's subjective and on no way affects performance with the marks or smooth. Many prefer that grooved looked

 It's a 160mm steel bike. If you care about the weight, this is not for you.

 @justanotherusername: Sure , the first thing we learned was not make unnecessary steps. If the customer had Rz numbers that bad we would let it just that way.

But because I was in the medical biz for most of the machining time I could not done it that way. Everything needed to be smooth as silk. Same for the food industry because they all want surfaces to be less sticky.

My CNC parts on my bike are almost free of marks. You need to look really close on the stem and only notice it when you are in the biz. The brakes, well you will notice but not that bad.

 @Serpentras: You dont mention one of the main differences between manufacturing a bike part and parts for the medical industry - cost, go find out how much your spindle time is per hr.

As I say, when you are paying the bill for the machine and costing the part, you wont want to spend a long time with your spindle maxed out running surfacing for absolutely no reason, especially when many people like the 'machined look' - its a sign the part has been CNC machined and not a cheap casting etc.

I think you are also confusing 'marks' with deliberate too-path patterning when surfacing - I would class a mark as the finish left on the floor by a flat end-mill or face-mill etc - I wouldnt class this as a mark, its a deliberate aesthetic choice.

It certainly hasnt done companies like Hope, Absolute Black and many others any harm anyway and it does bug me when machinists continually pop up saying 'In my job that Hope brake is classed as unfinished'.

 @justanotherusername: Exactly. “Finished” means consistent and in line with the intended aesthetic. Not an arbitrary standard of smoothness that machinist snobs pride themselves in achieving.

It would be different it if we were looking at random swirls from a fly cut, but in this case they specifically selected a small ball mill and patterned it to create a consistent and interesting pattern that matches the shape of the part. Some people won’t like the look and that’s fine, just like some prefer green to red. But saying it looks unfinished is disingenuous.

 @Blackhat: as a professional pinkbike machinist whos seen a real life lathe before, I think its beautiful.

 @Blackhat: the words you are looking for is stepover and cusp

 @justanotherusername: ouh dude, like I said those are the basics. Why do you want to talk to me again about the cost, I know to calculate that. We have the formula for that specific and it's the basic training you will receive before you even allowed to do anything.

I am not confused, by those marks. Thats just a ball instead of a end mill cutter. Very easy to replicate...

You are confused by what I wrote. Look Trickstuff up and then We Are One to get it. The stem almost got no marks. The Direttissima I have got some marks you can spot right away who are NOT intentionally made but can happen. I am way more onto that sleeker stuff like I said. Or just look at intended. Ofc you have the same benefits for this as stuff won't stick easy as those higer Rz surfaces.

This looks like it could be made by an older 3 axis CNC and is almost sleek anyway. Nothing special, there are other MTB projects where you instantly see that it's not possible this way.
A larger diameter then the ball for the end cutter to make the final cut to smooth it out takes way less time then the tiny ball going for a endless journey to create such a pattern. Even if this is an HSC. Both will fly anyway.
This is AL , we cut this right away to the finish. You dont even need a another tool to get it smooth.
This makes me a Snob? I dunno , so be it.
This kind of surface always will remind me of the old school end cutters with many teeth for the rough milling instead of the new ones with only one sharp edge per teeth. That is probably why in my mind it looks unfinished.

 @Serpentras: Good for you dude, some of us like the look, me included - and I’ll keep programming my machines so the parts look that way too when I feel like it.

And yes saying something ‘looks not done’ makes you a cnc snob, but that’s OK, we don’t all like the same thing.

 @Serpentras: I had to go back and look at the part. lol ... you're right, it looks like it has been finished with a ball mill. I can't recall (in 20+ yrs) ever seeing that, and it shrieks amateur.

I think finishing marks with a small endmill isn't ideal either. I prefer a larger finishing tool appearance, and notice most shops will do it.

 @njcbps: So you haven’t ever seen a Hope or Absolute Black part before then, eh? - amongst many, many others.

It was done to give an aesthetic appearance - a deliberate choice - Rideworks is a machine shop, I’m sure they know how to pick between types of tooling and if you haven’t seen anyone in 20+ years 3D surface a part and you are genuinely in the CNC industry.

Man you ‘CNC gurus’ are an odd bunch.

 @justanotherusername: you havent seen the discussions on new Macs from the raging fanatics makes cnc guys look positively gentlemanly

 @justanotherusername: I'm not a CNC guru, but have been around machining for awhile. I work in an industry that produces functional parts ... esthetics are always important, but ball mill finishing wouldn't be it.

I haven't seen Hope or Absolute Black parts before. I had a look at the latter, and don't like them. But that's only an opinion.

 @justanotherusername: yeh, most will dig that look. I get that. Gabaruk, Pole and even Propain but they used it to make a one piece asynchronous lower link you can't even see. I get that and it's sure a aspect of the design so it is ofc finished.

It's funny because before I was getting into the job I had already parts and items who are made with only a sleek finish. I had even an MP3 player back then who was CNC made and anodised. Super nice stuff even today.

 I'm pretty sure it is and although I can't imagine anyone knickers in a twist over this I've also seen the comment sections on reviews of Brassed Off the movie.

 @Bob-Agg: someone out there will be uttering “hold my beer” right now

 @BenPea: Honk.

 @BenPea: I mean, if someone has differing views, the competing model of bike designs itself: the "Maggie", a fully rigid bike, unforgiving ride, made of iron.

 @muumuu:

 @muumuu: And only goes in straight lines, no turning.

 @commental: not available in Argentina either

 @muumuu: and don’t forget the Boris bike, Fat and turd like.

 @kipvr: Been ridden in every corner of London and whored out to large banks for sponsorship? I think the Boris bikes do live up to their progenitor

 What's the next model name in the lineup - Battle of Orgreave? Picket Breaker?

 Was just about to say, shout out to the OG...

 If I was making a small scale full suspension bike, I'd probably model the kinematics on a good production bike. Way easier than the extensive testing to get them right. Not saying that's what this guy did, but it's a good strategy imo. And it's not like Giant would lose sales because of this tiny manufacturer. I doubt there's much overlap between people interested in this bike and people interested in a giant. He'd take sales from other boutique steel frame builders, like starling, cotic etc.

 Naha, the bottom shock mount is on the bottom rocker. Giant/old Trek spawn. Bet it rides amazingly.

 Reign has less travel and the suspension is different. They could have added links and put the shock upside down and sideways to make it look prettier and unique but I'm sure most looking for a bombproof steel full squish bike don't care.

 It's not the same layout as a Maestro system though. The shock is floating, with the extension of the lower link pulling it downwards, like a rocker arm.

 Why bother taking the time to leave a comment like this? Guy has worked his nuts off to produce this bike, stuck his cock on the block to pursue his dream of starting a bike company and you come along with a flippant comment like that. Nice one....

 This bike does have a tapered head tube. It looks straight and it is but the headset you put in it allows it to accept a tapered fork. It looks to me like it is a EC49 28.6 top and a EC49 40 bottom.

 I just realized you were talking about the aesthetic of the tapered head tube. Now that I’m not sure about.

 Not sure what "hype", the mainstream just simply won't buy em.
1) yes, heaps of loads there if you want that low TT.

2) Yes, but it's a pain to mitre so why bother as a 44mm headtube does the same job and is easier (read slightly cheaper) to use.

 they say eff. SA 78°, actual SA 73° on their website,

 It's been edited already! To...78.

Marketing department dropped their donut and sprinted down the hall slid across a desk and hammered "7" "8" with everything they had.

J/k I'm sure it's just Mr White, and big kudos for a beautiful bike...and seat tube on trend.

 @tofhami: True says so in the article now too, but it only had the 73° when it first posted.

 Have you been injured at work?, Been in an accident that wasn't your fault, call the Butterfield accident claim and dietary service now.

 @browner: i though tyou were going to say call the A team dur de de dur da da da

 @browner: quiche lorraine, mystery meat, bon bon bon bon... It's up to you.

 @TheBrickOriginal: sandwich casserole, potato grids, pork cylinders... the list goes on

 what a beaty

 probably cheaper than the new top of the range macbook

 @Compositepro: but man, that new top range macbook will run circles around my razer studio 17, and that cost $3600

 @hamncheez: yeah i was sat here waiting to take mine then saw the price lol