Discussion Topic |
|
This thread has been locked |
Jasper Young
Trad climber
Adelaide, South Australia
|
|
|
Dec 20, 2017 - 12:50am PT
|
Nothing unprofessional about the engineering, more just the way you continually sh#t on a design you see to be inferior.
|
|
couchmaster
climber
|
|
|
Dec 20, 2017 - 06:51am PT
|
I don't believe that questioning and extensively discussing a new design is shitting on it Jasper. If you don't want to hear it it would be easy to just move on. For myself, I appreciate Toms views on it, and he's right to question it. Repeatedly. Engineers will debate things like this until you get sick of heard about it, have you never gone on an extended climbing trip with some?
It is fascinating and interesting and goes on until you are sick of hearing it, but yet, they remain fascinated. That's why they are engineers and we get to enjoy the fruits of their labors.
If you look upthread, I would suspect that Tom also compliments the design. Not looking myself, don't care enough, but you might. These Merlin cams are amazing and have stripped all of what may be unnecessary off (and then some?) in an attempt to make the lightest cam that will work. Perhaps it was too much? It's a design that has some features not seen anyplace ever previously, so who can say? I love mine, time will tell of course. Carry on.
Regards
PS, great pics Studly!
|
|
ChrisRitna
Big Wall climber
Columbus
|
|
Seeing as this thread has been the catch all for big cams, I wanted to get yalls' opinions on the cam I am building.
First of all, Lets nip some questions in the bud:
I will not make any for anyone else (due to risk and copy write infringement)
I have a BS in Metallurgical Engineering and know the old saying that a BS Engineer knows just enough to get themselves killed.
I am not doing this as a cost effective way to get a big cam, just as a combination project of climbing and engineering that I find fun with the added plus of a big cam in the end.
I have a VG #9 on the way and will consider a Merlin #8 after a while of successful in-the-field use.
I do not nearly climb enough off width to warrant any of these cams, I just find gear collecting and having gear for any size crack to be fun.
I started thinking about making one back in July never figuring I would actually do it and noting that if I hit a large enough road block I'd probably just let the project die. I am now at the point of finishing the first 3D printed prototype for tolerance checks. after that I only really have the stem design to hash out which I have some ideas and would love to hear any ideas.
I am essentially copying BD's C4 #6 design and scaling it up to what would be a #7.5 in their numbering scale.
All values in Parentheses are the corresponding dimensions on the BD #6
I started by learning a free 2D open sorce Drawing software called LibreCAD and making the profile of bridge (the spacer between the inner lobes which connects the axles to the stem). One of my main concerns was stability of the cam when placed so I increased the depth (the Z dimension that is not shown below) to 70mm (42.5mm). This is where I chose to beef up the axle diameter to 8mm (5.5mm) and the support material around the axle. I also increased the axle seperation to 37.5mm (30.5mm). Hole in the center is just for weight reduction and the surrounding wall thickness is always larger than the BD #6
The box around the photo is 60mm x 30mm
Moved on to the Lobes where I started with taking the section of the 14 degree log spiral I wanted starting at r=95mm and going followed the curve for about 117 degrees, ending at r=158 ish. This was done by calculating ~600 points along the curve in excel, converting them to Cartesian coor. and making a spline along them. The cut outs were basically made arbitrarily but keeping their distance from any other edge more than 10mm. All cut out edges are concave to avoid stress concentration points. The axle guide cut out allows for 95 degrees of rotation raising the low end to r=105mm.
The box around the photo is 200mm x 150mm
All that comes out to a cam of a relaxed width of 279.5mm and max retracted width of 172.5mm (or 6.8" to 11.0"). A comparison graph can be seen below and the data is taken from the manufacture's website or, in the case of the Merlin #8, from earlier in the post.
This all ends up with a lobe that looks quite a bit bigger in comparison to the BD #6
As for stem design, I want to run a loop of cable through the bridge with the connection point above the bridge but have not looked into structural cable connections yet. I was going for a flexible stem that basically mirrors BD's design but loops through the top instead. If anyone has any experience or advice on doing this your help is greatly appreciated
That's basically where I am at now.
All Drawings available upon request in *.dxf file type though I take no responsibility as to what you do with them as I have done no testing as to if the designs are structurally sound in real world conditions.
|
|
Gnome Ofthe Diabase
climber
Out Of Bed
|
|
|
Jul 31, 2018 - 05:12pm PT
|
wait
I missed the last few pages of fun
]k' I still want one . . .no need thO . . .
your gear looks good, is it fully tried out yet?
your post is dated on
April Fools?
|
|
Jaybro
Social climber
Wolf City, Wyoming
|
|
I want one!
And ya, I know, I read the disclaimers.....
|
|
Gnome Ofthe Diabase
climber
Out Of Bed
|
|
I think we'all hurt -ChrisRitna's- feelings.
1st post, his 1 & only!?
& an April fools post . . .
So falling in the middle of the high spring season,
Jaybro's shoulder,
I went climbin' & got bann'd
Then Bird passed,
things went on & no one saw the plastic proto-type,
no luv = 1 post?
Yer' not from 'round her' or lurk'd much . . huh, Chris?
Yuh gotta gnow, it takes a tough customer to go all in for the whyid . . .
For Merlins or for Tom & his Giants, it is a mixture; a labour of luv to bring fun-ction, over time - for a price that makes sense
the need to build it your own self, is a practice in search of perseverance, a bit of support might still help
so that is what this is
or
TL:DnR:
Bump for big cams, innovation & Da'whyid !
|
|
Trashman
Trad climber
SLC
|
|
Reason 4381 for technical discussions of cam designs
I’m on record in this thread supporting both big cam manufacturers, as well as encouraging Tom’s technical discussions. The above thread shows why.
Far too many new consumers look at a CE(or UIAA, 3 sigma, etc) mark and assume all the options on the market are the same. They’re not, all have potential strengths and weaknesses. If you’re unwilling to spend time understanding those differences, and want to blame the manufacturer for the consequences, I suggest taking up a more forgiving sport, like bocce.
|
|
ChrisRitna
Big Wall climber
Columbus
|
|
|
Sep 21, 2018 - 09:04am PT
|
Been a while but no this was not an april fools joke.
I out sourced for the machining of the lobes.
Had them rough cut out of 6061. They all need a lot of finishing work but they look great what I asked for. I plan on getting a pair of them anodized to match BD color system
I ended up getting the full thing 3D printed so I dry fit the lobes with the plastic prototype pieces.
I just got the axles in today so I will be fitting them later.
They are just 8mm 304 stainless rotatory rods with M6 threads on either side to attach an axle cap plate.
The bridge is being machined by a guy I found on reddit (real smart, I know)
He thinks it will be done sometime next week
|
|
Jaybro
Social climber
Wolf City, Wyoming
|
|
|
Sep 21, 2018 - 10:33am PT
|
Very cool!
|
|
thebravecowboy
climber
The Good Places
|
|
|
Nov 28, 2018 - 05:34pm PT
|
it didn't break....
|
|
Matt's
climber
|
|
|
Nov 28, 2018 - 05:35pm PT
|
Interesting alexey-- I assume this is because the stem is a solid rod rather than a cable? I wonder if you can just straighten out the stem after this...
|
|
Clint Cummins
Trad climber
SF Bay area, CA
|
|
|
Nov 28, 2018 - 06:46pm PT
|
Looks like using the Merlin as a "pusher cam" worked great on Brother From Another Planet.
Yep, just straighten the stem.
Having the bendable stem is another degree of freedom which helps prevent the cam lobes from bending.
|
|
edavidso
Trad climber
Oakland, CA
|
|
|
Nov 28, 2018 - 10:00pm PT
|
The stem can bend in an off-axis fall when the lobes are not able to rotate to be inline with the direction of fall. Even if you rest on the cam in an off-axis placement, the stem will most likely bend. The amount of bend will be directly related to how off-axis the cam has been placed. For large off-axis placements such as the one taken by the cam in the video, the lobes can also bend depending on how open they are. If the stem bends, you can just bend it back to straight. Bent lobes will usually cause the cam to stick rendering it useless until lobes are replaced. In the past couple years, I have only seen this once on the fall referenced in the video. Most off-axis falls are not as extreme and cause the stem to bend only a few degrees. Wire rope stems on smaller cams will do something similar, but is commonly known as "kinking".
When this fall happened, I estimated that the stem was bent by about 20 degrees. I did a simple test to determine how many of these types of falls could be taken before the stem breaks. A final bend angle of 20 degrees required bending the stem to 35 degrees (15 degrees of springback). Bending the stem back and forth 35 degrees in each direction is the worst possible scenario for fatigue. I did this until the stem broke. None of the four stems tested broke in less than 60 cycles. So if you're taking numerous falls that result in the stem being bent by 20 deg, please send the cam back to me for stem replacement after ~30 such falls. Of course, this practice will probably be self-limiting by bending the lobes at some point. The important thing to know about fatigue failures is that fatigue is highly non-linear, meaning that exponentially higher lifetimes are realized by smaller bend angles. In other words, if you place the cam inline with the direction of fall and the fall does not cause any stem bending, you can take millions of such falls without breaking the stem. If you're bending the stem by a few degrees, you should be in the thousands of falls, etc. Moral of the story: do your best to place cams inline with the anticipated direction of fall and in a location where they can rotate to the direction of fall.
|
|
couchmaster
climber
|
|
|
Nov 29, 2018 - 05:54am PT
|
@8:45 in Alexys linked video, that's some hard looking offwidth - the struggle is real....
|
|
Matt's
climber
|
|
|
Nov 29, 2018 - 11:23am PT
|
as usual, thanks for the reply edavidso.
|
|
Jon Beck
Trad climber
Oceanside
|
|
|
Nov 29, 2018 - 11:45am PT
|
Wouldn't it be better to just leave it bent? Or would a fall on a bent shaft put an unequal load on the lobes putting them at risk?
|
|
NutAgain!
Trad climber
South Pasadena, CA
|
|
|
Nov 29, 2018 - 12:03pm PT
|
That is some hard-core burly groveling in that video!
|
|
Alexey
climber
San Jose, CA
|
|
|
Nov 29, 2018 - 12:48pm PT
|
Matt's
climber
Jun 27, 2017 - 09:39pm PT
I received mine today (#14).
Unreal build quality, unreal weight. When the lobes are locked, its more compact than a #5.
Clearly someone smart put a lot of thought into the design.
No disrespect, but a valley giant looks like a high school shop project compared to this thing.
Matt, still think that #9 VG is "high school shop project " in comparison with Merlin? I actually now think the opposite after watching what small fall can do with the cam.
always think that versatility is superior to weight in the cams world
|
|
Matt's
climber
|
|
|
Nov 29, 2018 - 01:22pm PT
|
Matt, still think that #9 VG is "high school shop project " in comparison with Merlin? I actually now think the opposite after watching what small fall can do with the cam. I always think that versatility is superior to weight in the cams world
The merlin i have has much higher machining/build quality than the valley giants I've used in the past. To my untrained eye, the VG looked like something I could build myself. All that being said, the valley giant design is tried and true over the years. For all I know, the merlin design could be a beautifully made piece of junk! I plan on using the merlin only expecting it to hold body weight, and I'm fine with that.
|
|
|
SuperTopo on the Web
|
Let us know!