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Building a Cam

Original Post
Kevin Brooks Henry · · Minneapolis, MN · Joined Jan 2010 · Points: 685

This tri at my school I chose to take manufacturing with metals as my elective. We pretty much have free reign over what we get to build, so I decided to build a cam (won't actually use it of course). Yesterday I ordered the Aluminum (6061) and a took apart a gear4rocks cam (scarily easy) to salvage the axel and springs. When the aluminum arrives I will start building and keep this post updated with pics, etc. If all goes well, I hope to end up with a rigid stem cam with a range slightly smaller than a number 2 camalot.

Stay tuned
KBH

Bill M · · Fort Collins, CO · Joined Jun 2010 · Points: 317

Do you have access to a Lathe and/or a 4-axis CNC machine? I am a BSME / MS Metallurgy, I don't see any reason you can't build a cam I would climb on. What type of mechanical test equipment do you have access to, an Instron or MTS?

Nathan Stokes · · Unknown Hometown · Joined Oct 2008 · Points: 440

I can see scavenging the springs, but why the axle?

Gregger Man · · Broomfield, CO · Joined Aug 2004 · Points: 1,759

Yup.
Rigid stem with no welds or swages to fail and you'll be good to go.
Pad the dimensions found on store-bought models and you can put a little faith in it.
I think it was Aric Datesman that gave me the idea of testing it using a 'circuit-breaker' technique where you could use accessory cord with a known strength and pull until that breaks. That way you can give it a limited stress test without destroying it. (1 strand of 5mm cord with clove hitches at each end will break somewhere around 4-5kN. Not precise at all, but it can give you a warm fuzzy feeling about your handiwork.)

Woodchuck ATC · · Unknown Hometown · Joined Nov 2007 · Points: 3,280

Sounds fun... think big. Go for a 36 inch span if you can..protect those nasty chimney moves.

Bryan Ferguson · · Unknown Hometown · Joined Apr 2008 · Points: 635

We climbed the wide pitch on Blocktop with home-made cams, thanks to Greg D. Greg is a master and machined two #8 cams in 1983. I stacked them with wood blocks on pitch four. The pitch goes free now but we never would have nailed the FA without Greg’s cams. To shape the cams (lobes) Greg simply drew rays from the axle and then extended the rays beyond the #4 Friend's lobes until he thought he had the dimension we needed. He did well.

http://www.mountainproject.com/v/block-top/106151030

Locker · · Yucca Valley, CA · Joined Oct 2002 · Points: 2,349

A 16yr old kid building a cam.

There IS, hope!

LOL!

EDITED:

or 18yr now? Same deal though. Still COOL!

Kevin Brooks Henry · · Minneapolis, MN · Joined Jan 2010 · Points: 685

Hey everyone, thanks for the replies! Pretty psyched to get working on this.

Bill- as far as I know, i don't have any testing equipment at my disposal, to test it I will probably go with the circuit breaker method described by Gregger man.

Nathan- I was originally going to build an axel, but I used the gear4rocks lobes as a template for designing my lobes, so I figured having an axel already built for something like them would be easier.

Woodchuck- if only I had enough aluminum. I am considering making a set of novelty lobes maybe in the BD #6 range if I have enough time and metal left over.

Locker- thanks, still 16.

Aric Datesman · · Unknown Hometown · Joined Sep 2008 · Points: 145

Good luck Kevin.

A bit late to suggest it, but Rock Empire cams come apart just as easily and are a bit nicer than Gear4Rocks. In either case be aware you're looking at metric holes for the axles (100% certain on RE, suspect it on the G4R), so pick your drill accordingly. A bit of clearance between the lobe and axle is needed, but not much (think 0.003" at most).

I should have a copy of the article I wrote ages ago on building a cam with nothing more than a hacksaw, drill and file, tucked away somewhere and if I can find it will post a link (was on RC but removed when I left the site). IIRC it was #3 size, cost ~$30 to build and the sample broke at 19 or 20kN. Took me a couple hours start to finish to build.

Kevin Brooks Henry · · Minneapolis, MN · Joined Jan 2010 · Points: 685

UPDATE:

Metal arrived yesterday, brought it to school today and began working on it. Got the stem cut out and a hole for a sling drilled. The other marks on the stem are where I plan for the trigger to go and the Axel. Haven't finalized the marks, just a rough guide right now.

Start of Cam

Woodchuck ATC · · Unknown Hometown · Joined Nov 2007 · Points: 3,280

looks big from that view...dimensions please?

Kevin Brooks Henry · · Minneapolis, MN · Joined Jan 2010 · Points: 685

sorry, forgot. dimensions right now are 5.5 inches long by 3/8 inches thick by 1/2 inches tall. Will probably change a bit though after sanding.

cms829 · · NJ · Joined Aug 2011 · Points: 90

are you wearing climbing shoes in metal shop? haha

Kevin Brooks Henry · · Minneapolis, MN · Joined Jan 2010 · Points: 685

UPDATE:

Finally got back to work today after having to spend all of yesterday finding parts for the milling machine that hasn't been turned on in 2 years. Got the trigger hole machined out and also got a hole for the axel drilled. Also had enough time left to add the axel, which fits in the hole without sliding around. Machining the trigger hole took off a little more metal on either side than I would have liked, but since I don't really plan on using it and don't want to go to the trouble of machining another stem I think it is fine.

side view of stem with trigger hole cut out

Top view of stem with axel

Alex Swan · · West · Joined Dec 2011 · Points: 25

Nice work bro! Keep the updates going! I'm excited to see how your cam turns out!

rogerbenton · · Unknown Hometown · Joined Sep 2011 · Points: 210

this is awesome!

how thick is the remaining aluminum around the trigger slot?

fossana · · leeds, ut · Joined Apr 2006 · Points: 13,318

Cool project!

Came across this 2009 link to Trango's homemade cam comp. Maybe they should resurrect a 2012 version.

I bet if you wrote to BD QC Labs they'd test if for you.

Aric Datesman · · Unknown Hometown · Joined Sep 2008 · Points: 145

Just FYI, Kevin- when slotting on the mill you're best off first using a smaller size endmill to get the bulk of the material out and then finishing with the final size endmill or (better yet) keep using the smaller endmill and offset the work to either side to achieve finish size. Less force on the cutter this way and you'll hold better tolerances. Oh, and there's no need to slot full depth in one pass...

fossana wrote:Came across this 2009 link to Trango's homemade cam comp. Maybe they should resurrect a 2012 version.
Chances of RC doing that are basically 0, unless they can find someone else with test equipment willing to donate the ~100 hours it took for me to run it in 2009. I simply don't have that much free time anymore, and gave up on RC. Btw, It fell through in 2010 when the sponsor went goofy and DDT didn't seem to have any interest in finding another. Not that he bothered to tell me until right when the comp was supposed to start and I had spent 2 months talking it up/finding people to compete.... Sigh. RC really was a better place under J_ung's rule, and he and I had a blast with the 2009 comp.
Gregger Man · · Broomfield, CO · Joined Aug 2004 · Points: 1,759
Aric Datesman wrote:...there's no need to slot full depth in one pass.
ditto.
I was cutting 0.015" passes with a 0.125" end mill.
CO_Michael · · Unknown Hometown · Joined May 2008 · Points: 956

Looks like you are making some good progress.

Ken Noyce · · Layton, UT · Joined Aug 2010 · Points: 2,648
Aric Datesman wrote: Btw, It fell through in 2010 when the sponsor went goofy and DDT didn't seem to have any interest in finding another. Not that he bothered to tell me until right when the comp was supposed to start and I had spent 2 months talking it up/finding people to compete.... Sigh. RC really was a better place under J_ung's rule, and he and I had a blast with the 2009 comp.
Fell through, I think not, I was clearly the winner of the 2010 Homemade cam comp (even if it was by default since I was the only contestant;).
Guideline #1: Don't be a jerk.

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