NorCal Kayak Anglers

Kayak Zone => Kayaks => Hobie Kayaks => Topic started by: NowhereMan on April 10, 2014, 08:04:56 PM

Title: DIY V1 mirage drive shafts
Post by: NowhereMan on April 10, 2014, 08:04:56 PM
I've been wanting to experiment with different length pedal shafts (or cranks or whatever they're called). So, I got a pair of 15" 6061-T6 aluminum 3/4" bars (about $10 for the pair). That's about 2" longer than the stock length.

I decided to use 1/2" bike pedals, so I got the appropriate taps (a standard bike tool for cleaning up threads). I borrowed my neighbor's (tabletop) drill press and drilled 3/8" holes for the bolts on the bottom, 5/16" holes for the adjustment peg, and 29/64 holes for the pedals. It was fairly straightforward to tap the pedal holes, and I bought some cheapo pedals.

The right shaft is perfect. Unfortunately, I measured incorrectly on the left one, and the 5/16 hole didn't line up (metal is very unforgiving). I drilled it out a bit to get it to fit, so I can test it out. I'll post again once I get a chance to try it---with luck, that'll be within the next few days.

If I like the length, I'll redo the left one. In any case, I'll probably also test a couple other lengths. I think I've got the process down pat now, so additional ones should be a piece of cake (famous last words...).

Let me know if you have any questions.
Title: Re: DIY V1 mirage drive shafts
Post by: Tote on April 10, 2014, 09:01:57 PM
Where did you buy the aluminum bars?
Title: Re: DIY V1 mirage drive shafts
Post by: Great Bass 2 on April 11, 2014, 07:45:53 AM
Wow that's awesome. I have a pair of 7075 aluminum bars, to be drilled, could you help me? Also, are you going to get them anodized?
Title: Re: DIY V1 mirage drive shafts
Post by: Danglin on April 11, 2014, 07:50:30 AM




                                                                                                                             Wow….
Title: Re: DIY V1 mirage drive shafts
Post by: atavuss on April 11, 2014, 07:54:20 AM
Might be a stupid question but what is the advantage to the longer solid stock?  Stronger?  Is more leverage going to expose a weak link somewhere else down the line? 
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on April 11, 2014, 08:22:33 AM
Where did you buy the aluminum bars?

I got the aluminum at "Gorilla Metals" in Santa Clara, near the SJ airport:
http://www.gorillametals.com/
I've gotten metal from them a few times now and they've always been very professional. For small stuff like this, you can usually just drop in and they'll cut it  then and there.
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on April 11, 2014, 08:30:10 AM
Might be a stupid question but what is the advantage to the longer solid stock?  Stronger?  Is more leverage going to expose a weak link somewhere else down the line?

I usually use the number 6 setting for the pedals, but I like to also use 7 once in a while. When I put it at 7, my heel tends to just barely bump on the boat before the pedals bottom out. So, that's what got me thinking that longer cranks might be useful. In looking online, I found one guy who'd made 15" arms and liked them, so that sounded like a good starting point. If there's more leverage, that's just an added bonus. Due to the failure issues with the hollow cranks, I figure that longer ones should definitely be solid. And besides, solid bar is much easier to find.
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on April 11, 2014, 08:51:18 AM
Wow that's awesome. I have a pair of 7075 aluminum bars, to be drilled, could you help me? Also, are you going to get them anodized?

One concern is that cutting the threads in 7075 might be pushing the limits of the taps I have. They are actually not designed to cut fresh threads, just to "chase" threads in bike cranks. If I had it to do over again, I'd get the 1/2 x 20 taps from, say, McMaster-Carr (they do have both right-hand and left-hand threaded versions), instead of the Park Tool version. They are about the same price.

Let me do another set first, just to make sure I've got the process down. Unfortunately, it might be a while before I get to it, since I've got a never-ending deck project that keeps interfering with all of my fun...




Title: Re: DIY V1 mirage drive shafts
Post by: dilbeck on April 11, 2014, 11:34:37 AM
We've got to talk because this might be the solution to my issue.

And I'm just 10 minutes from the airport.  Thanks so much for posting this!

Title: Re: DIY V1 mirage drive shafts
Post by: WingShooter on April 11, 2014, 02:18:48 PM
I want a pair!!
Title: Re: DIY V1 mirage drive shafts
Post by: bmb on April 11, 2014, 02:21:30 PM
We've got to talk because this might be the solution to my issue.
Which of the myriad of your issues are you talking about?
Title: Re: DIY V1 mirage drive shafts
Post by: dilbeck on April 11, 2014, 03:00:20 PM
We've got to talk because this might be the solution to my issue.
Which of the myriad of your issues are you talking about?

I'll get pictures this weekend but basically the long bolt that goes through the shaft and then the pedal pulled through the shaft.  I know that doesn't exactly paint a clear picture but it's the best I can do.  Pictures will help.

Title: Re: DIY V1 mirage drive shafts
Post by: lucky13 on April 11, 2014, 04:50:29 PM
By extending the bars, doesn't it mean you'll have to raise your legs up even higher? With the factory bars, the sitting position makes my butt sore after an hour or so because it puts too much pressure on my ass. I think it would be even worst if my legs need to be raised another 3-4 inches while pedaling.
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on April 13, 2014, 09:46:00 AM
By extending the bars, doesn't it mean you'll have to raise your legs up even higher? With the factory bars, the sitting position makes my butt sore after an hour or so because it puts too much pressure on my ass. I think it would be even worst if my legs need to be raised another 3-4 inches while pedaling.

I owned a recumbent bike for several years and we called that "recumbent butt". It seems to come with the territory.

Among recumbent bikers, the ideal butt-to-pedals angle is a very personal thing. Some recumbent riders have pedals that are above head-height which puts more of the weight on the back, and thus (they claim) offers some relief to the butt. On the other hand (or is it "cheek"?), some riders want the pedals well below butt-height. By those standards, a couple of inches is small potatoes, but I'm hoping that longer equals slightly more heel clearance and it will certainly give a little more leverage and a slightly longer throw. And besides, it's a fun thing to experiment with.

I plan to make at least one more pair of cranks (gotta make use of those taps...). When I get to that, I'll try to remember to make a video. There are a couple of small points (hard to explain, but easy when you see them), that will probably make it go a lot smoother if you decide to give it a go.

Title: Re: DIY V1 mirage drive shafts
Post by: charles on April 13, 2014, 10:49:29 AM
Bike cranks are offered in different lengths to suit different body types. Short and medium riders generally have a shorter crank while tall long legged riders have longer ones. This option allows the leg/knee to obtain a comfortable crank revolution and power efficiency with each pedal turn. Hobie has a one size fits all and uses seat adjustment and their one through seven pedal shaft adjustment system to accommodate different body types. This works for most of us but I can really see the point of the tall guys needing a bit more pedal shaft length to increase comfort and efficiency. With increased length comes greater leverage and torque so solid shafts are a must. Glad to see the experimental upgrades coming out of this group.
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on April 19, 2014, 12:25:12 PM
I've made a second set of crank arms. I did things a little different this time, and I think I've got the process pretty much dialed in. IMHO, the secret is to make a template instead of trying to measure things directly on the aluminum bars. A template makes it easy to get consistent results, things go a lot faster (once the template is done, that is), and mistakes are a less costly (and less frustrating). Best of all, I believe I've found the ideal template material. An aluminum channel is available that is 1" wide with 1/8" thick walls and square corners. So, it's exactly 3/4" inside the channel and it slides over the aluminum bar, with only an infinitesimal amount of play. This is the stuff:

http://www.metalsdepot.com/products/alum2.phtml?page=6063%20aluminum%20channel&LimAcc=%20&aident=

I think the "C31-1218" is what I've got. A 6" strip is all that's needed but it took me 3 tries before I got it right. The measurements need to be dead on---the spacings are given on the attached pdf.

I've also attached a couple of pictures of the template and the finished crank arms. Note that the adjustment pin is centered in the plastic hole. Also, both crank arms are identical, except, of course, for the left-hand threads vs right-hand threads for the pedals.

Unfortunately, I still haven't had a chance to try them out, but will report back when I do. However, it's looking like that might not happen until rockfish season opens.

Title: Re: DIY V1 mirage drive shafts
Post by: charles on April 19, 2014, 12:42:23 PM
Looks really good. I'm sure you will happy with the water performance. A template for the bottom two holes is the smart way to go. The pedal holes are not as critical except for needing to be dead center in the solid aluminum shaft.
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on April 20, 2014, 11:16:12 PM
I've added a couple of drill bits to my arsenal and I think I can now make these semi-efficiently. So, I'd be glad to make a few sets of V1-like crank arms for NCKA'ers who might want to try something different.

If there is interest, I'd like to do them all at once, since that will take way less time than doing them separately. I can pick up the metal bars (6061-T6 aluminum), and I'd drill and tap them for you. You'd still have to do a little filing (bottom corners need to be slightly angled, and the ends might be a bit rough), clean/polish, and add pedals. Note that I've only got taps for 1/2" pedals, so you'd want to be sure you can find pedals you like in that size.

I'm not looking to make any money, so no charge for my time---you'd just pay for the cost of the metal bars (roughly, $10). For me, it's more like a science project to see how they hold up over time. PM me if you're interested, and let me know what you have in mind. I'll probably only have the drill press for a few more days, so this will have to happen soon.
Title: Re: DIY V1 mirage drive shafts
Post by: dilbeck on April 23, 2014, 10:07:25 AM
PM sent.

Title: Re: DIY V1 mirage drive shafts
Post by: Great Bass 2 on April 23, 2014, 10:22:04 AM
Can you do 7075 aluminum?
Title: Re: DIY V1 mirage drive shafts
Post by: AlsHobieOutback on April 23, 2014, 10:38:45 AM
Really like them and wish I could get 3-4 pairs  :smt003  Thanks for the post!
Title: Re: DIY V1 mirage drive shafts
Post by: Sharkie on April 24, 2014, 08:28:36 PM
Great subject. ...And another point. ...CLIP IN BIKE PEDALS.  I am sure for those who spend more than average time on the water clip in shoes and pedals will be an excellent advantage. They make for cyclist warm weather sandal type shoes that can clip in. Go online and check out the shoes and pedals. The fit with the stock Mirage drive pedals is not perfect...and bit sloppy, depending on what type of shoes one wears. With a soft sole dive bootie one can get sore bottom of the feet. Clip in bike sandals would fit great, with or without socks.
   And good point about changing the length of stroke on the Mirage drive....throughout the day. I have spent 6 hours straight on the ocean....have had sore butt, so I changed the length of stroke and that helped.
   The length of the arms was covered well by Charles. Not sure if a longer length would be good for me...5ft 9in. Taller persons I guess could use a longer length of arm...or at least try.
   Keep the ideas coming in! Thanks, Ron
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on May 01, 2014, 09:46:18 PM
I finally got a chance to try them out today. I gave my 15" cranks a decent workout, pedaling from the Santa Cruz harbor almost to the Capitola wharf and back, mostly at a slow trolling speed. I don't have the exact distance, but I'm sure it was at least 3 miles each way. I made a brief (really boring) video:

https://www.youtube.com/watch?v=qKPlxKWahZ4&feature=youtu.be

For the last half mile or so, I went faster---not all out, but as fast as I figure I could expect to maintain over a substantial distance.

I definitely like the crank arms and have no plans to switch back to the stock setup. In fact, I might experiment with even longer ones just to try to dial it in. My (completely subjective) impression is that the added length makes for slightly more efficient pedaling and it also seems to take a little pressure off the butt. Another positive is that the bike pedals reduced the tendency of my feet to slip as compared to the Hobie platform/pedals, in spite of the added length.

I didn't notice any real negative, but based on my recumbent biking experience, I'd expect that moving the feet up can cause toes to go numb more easily. I always get a little of that when I troll for long periods without a break, and it didn't seem any worse (or better) than usual.

Note: I changed the link to a slightly better version of the video. For some reason, the original video was especially blurry.
Title: DIY V1 mirage drive shafts
Post by: AlexB on May 08, 2014, 05:14:50 PM
RAP - I see where you're going with the clip in pedals (which are strangely called "clip less" pedals), but I think that is a VERY bad idea.

How many times have you seen a novice cyclist topple over at a stoplight with both feet stuck to his pedals? It's funny (and only mildly painful) on a bike, but could be a SERIOUS problem on the water. Add in some saltwater exposure and corrosion to your clipless mechanisms, and you could be in serious trouble if things go south.

Probably not an issue for people who are experienced with clipless pedals (I like the Eggbeaters, myself), but probably a bad idea for people who don't spend much time on a bike.
Title: Re: DIY V1 mirage drive shafts
Post by: ppickerell on May 08, 2014, 06:05:17 PM
$10 FOR A SET? I will give you $20 for a set as a PIF for your efforts! A little longer than stock length suits me as I am 6'4" and sport extra ballast leeward :smt010

Not to be a shit disturber but if you are going to get any warranty work done on your drive, switch back to the stock length LOL.
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on May 27, 2014, 07:58:09 PM
Just a quick update, as I've been out several more times with these 15" crank arms---the last 3 times in less than ideal conditions. I still like the mod a lot and there's been no down side. When time permits, I'll experiment with slightly longer lengths, like 16" and 17". I'm betting that 16" will be optimal.
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on September 14, 2014, 05:10:35 PM
Yesterday, I was going to remove the crank arms for some routine maintenance. The left one came off without a hitch, but the right one was another story. The stainless bolt that holds the arm onto the drum would not budge. I used a fair bit of force, but didn't go all out, since I don't want to damage the plastic drum. I'm guessing there must be some slight galvanic corrosion, although it is strange that the other side looks good as new. Anyways, it still works fine, so I'm going to wait until the off season before I use more serious force to separate it.

So, if you're using solid aluminum crank arms, I'd strongly suggest that you liberally grease the area where the SS bolt passe thru. Even with that, it would probably be a good idea to remove the bolt regularly to check that no problem is developing.
Title: Re: DIY V1 mirage drive shafts
Post by: Lost_Anchovy on September 15, 2014, 11:54:38 AM
A true kayak fisherman. If there is a problem we will figure out how to fix it before the manufacturer does.
Good work on the write up. You're quickly becoming a superstar on the forums with the Salmon video's and tutorials.  :smt044 . Thanks for sharing.
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on September 15, 2014, 12:01:07 PM
A true kayak fisherman. If there is a problem we will figure out how to fix it before the manufacturer does.
Good work on the write up. You're quickly becoming a superstar on the forums with the Salmon video's and tutorials.  :smt044 . Thanks for sharing.

Thanks, but I've only got 2 salmon so far. Hopefully, it'll become a habit...

Btw, it seems that for 2015 Hobie will use hollow crank arms, but with thicker walls than previously. I suspect that'll solve the breakage issue.
Title: Re: DIY V1 mirage drive shafts
Post by: NowhereMan on December 09, 2014, 07:52:58 PM
Another quick update...

I took the troublesome crank to a bike shop and got the one stubborn bolt removed. Then I took the whole mirage drive apart, cleaned and greased everything and put it all back together. There was a little bit of surface rust on the pedals (they are just a cheap $10 variety), but everything else looks good as new. That's pretty much all there is to say for season 1 on these crank arms. I'm expecting to get many years of service out of them.

For next season, I think I'm going to try spacing the pedals a little farther apart---more like a real bike. I guess I can't help but tinker with it... Anyways, I'll let you know how that goes.