First RC build Jamis Dakar 3220 w/Davinci drive

[biohazardman]

Well I finally found a bike that I thought would werq well for a mid drive type motor install. So grabbed it up off of Craigslist Speedo says 104 miles although it's ten years old. I have to believe it as they cables have not even worn through the paint yet. Tires still have the nubs on them. Was happy until I went to clean the dust off and found the crack in the head tube. Looks like it was done when the headset was installed/removed? Guess I will have to weld it up although I have not done much welding I have managed to do well on all repairs I have made thus far. Yes I know the 7005 aluminum temper will be affected but I really don't think that will be a problem in this spot. Anyone in the know think different?

I have not yet decided on L hand or R hand drive nor on chain or belt. I would like to hear some on the plusses and minuses of each so chime in with what you have done. Any links to drive train parts, pulleys, belts, chains, sprockets, ect. if have them would be appreciated.

Thought on mounting at the beginning was to run a 24 inch wheel and put the motor in the space vacated by the 26 inch unit. Not sure if the room is there though. Ideas on mounting would be helpful as well.

[mdd0127]

I would not weld that. You don't want to take the chance of affecting the temper. What I would do.....and could easily do for you is make an interference fit support ring that you heat up a little and press over the top of the head tube. Get me an exact measurement of the outside diameter of the head tube and a measurement of the height above the top tube. I have the stock and could turn you a support ring pretty easily. 3220's make things go fast! Don't take chances.

[dnmun]

you may wanna contact the manufacturer of the bike and ask them if they will exchange it for another bike. send it to their legal department, or send a copy of the letter to their lawyer and ask them to replace it and use your bike for manufacturing quality control analysis.

to discover the possibility of a weakness in their build is something they would likely cause them to be willing to swap out a bike with you. doesn't really cost them anything since other wise they are gonna be destroying other bikes to see stuff like what you have already. make sense?

maybe they will just swap frames, but for them a whole bike is just the same. only costs them $50 to build, shipping is more than that.

[biohazardman]

dnmun,
Not the first owner and it's 11+ years old. Think I'm stuck with it.


mdd0127,
Hold that thought I may take you up on it. 7005 can be heat treated to improve it's strength again after welding or so I have read on the internet so it must be true. Also I don't think a catastrophic failure will occur from a loose head set. More like I will notice it pull over see the problem and ride home slowly. Seldom ride over 20-25MPH anyway probly one ride to get max speed and take my rightful place in the ebike insanity club will be about enough. I think that a support ring in addition to welding would be in my best interest. What are your thoughts on that?

[mdd0127]

dnmun,
Not the first owner and it's 11+ years old. Think I'm stuck with it.


mdd0127,
Hold that thought I may take you up on it. 7005 can be heat treated to improve it's strength again after welding or so I have read on the internet so it must be true. Also I don't think a catastrophic failure will occur from a loose head set. More like I will notice it pull over see the problem and ride home slowly. Seldom ride over 20-25MPH anyway probly one ride to get max speed and take my rightful place in the ebike insanity club will be about enough. I think that a support ring in addition to welding would be in my best interest. What are your thoughts on that?

I still wouldn't weld on it. Heat treating aluminum properly involves a solution heat treat and artificial aging. Two separate processes that consume a LOT of energy. Usually it's between $600-900 just to get that done, unless you can get it in with someone else's stuff, find a shop with small facilities, or get a buddy deal, and even then, you still have to worry about warping.

Even though you won't be going fast, you are going to be adding weight. The lightest I could get a 3220 powered rig with 15ah of lipo is 75 lbs which adds significant stress to the frame. Also, where that crack is, if you do hit a deep pothole, curb, try to bunny hop or jump it, even at 25mph, the stress will focus on that area and you could have catastrophic failure. Look for the video of the guy riding down the volcano to see what it looks like when your fork comes off. Thin aluminum generally doesn't bend a little when it's already cracked and stressed way beyond it's limits. It just breaks.

Bikes are designed using the thinnest materials that will do the job for an average rider, at average weight, and average speeds. You'll be exceeding all of those parameters just by the nature of what you're building so take it seriously.

I'm trying to sell my shop and tools as hard as I can so this is a limited time free offer. Just get me a couple of measurements and your address and I'll mail you your best solution with installation instructions by the end of the week.

[fizzit]

Just sayin', I rode several hundred miles on a bike with a cracked and bent headtube without any problems. I ran into the side of a car at 25mph and didn't have money to replace the frame fora while.

[Thud]

Bio,
from a mechanicle standpoint. mdd0127 is spot on.
I would recomend a steel ring with a "just fits" slip on/tap in place & a high performance epoxy to keep it in place.
I like alloy frames but they are throw away after reaching their stress limits & starting to get fragile.

[recumpence]

From my standpoint, I would also machine a ring that would press-fit around the headtube (once the powdercoat is removed). I would find the highest strength epoxy and epoxy the ring around the headset ridge on the head tube. Heck, you may as well do the top and bottom considering the crank could propogate. That will be a permanent fix.

Matt

[lostrack]

Tricky one. Cracks grow on Aluminium so if you must fix it, make sure you do more than the bare minimum.

Also - does anyone want to chime in on using different metal types in a friction fit? I think they have different thermal expansion rates, which might cause a problem down the line.

If it was me I'd get a new frame...it's a pain now but the frame is the foundations for the build.

[Thud]

Thermal expansion is the least of the worry...
galvanic corosion will get you eventually if you use steel without planning for it....
I'd drill a releif hole to stop the crack from traveling. (1/32" would be plenty)

[dnmun]

what about using epoxy and wrapping the tube with high tensile steel wire in the epoxy, as tight as possible to just stop the crack from propagating. then wrap tape over it.

[mdd0127]

An interference fit aluminum ring would be perfect, no mess, easy install, no corrosion/expansion issues, easy.....Just need a couple of measurements and an address for shipping .

[biohazardman]

OK I will get the measurement tomorrow and drill a small hole to stop the crack as well as use this for a temporary build. Another ring around the tube below the head set possibly as well but it will have to be very thin as there is not much space there. Looking at a nice new Giant 29er but it's a couple months away. My Giant weighs in under 60lbs with 2x 4.6 ah 66V packs so I will try to keep this one near that. Arms don't werq well, specially after the crash in the snow, so no bunny hopping for me. Bummer I made the purchase at night and did not notice the crack in the first place.

Thanks guys for the help at stage one.

[biohazardman]

I got this in the mail today lucky me! Wunder where it came from? ;^) Brother ,who will be a welding inspector next month, says collar the head and sell the bike. I am beside myself but several here have said near the same so it will be. That means this build ends like the Giant BMC 400 in an unfinished bike and waiting for parts to start again. That's two out of five builds ending in failure one broken frame, one dropped motor. That's $800 for nothing thus far, although this bike may get me a few hundred in return once I fix it.

So now the search for another willing bike begins once again. Guess it will probly be new can't trust craigslist.

[MattyCiii]

Man, look at that DaVinci drive! Nice!

[GITech]

Man, look at that DaVinci drive! Nice!

BHM, uhhh, my ears are poppin!!! Why is it I get so pissed when I see such awesome stuff!?!

Nuvinci/DaVinche .. is it a typo or?..I haven't read'up these topics yet!?

Awesome,
GIJay

[Philistine]

Nuvinci/DaVinche .. is it a typo or?..I haven't read'up these topics yet!?

The Davinci is the name Matt S has given his latest reduction drive (the one pictured). A Nuvinci is the continuously variable transmission hub produced by Fallbrook. Totally different things.

The Davinci looks the business though doesn't it? I am a raving-rampant-frilly-collared-pink loving-flaming-Frocko, and even I get a stirring in my pants when I look at it.....

[GITech]

LOL! and I never type "LOL"!!!

RRFCPLFF'o ...OMG, that's a first!

Thanks, >.<
Jay

[biohazardman]

Well the build is on again. Found another frame not as nice as some but the motor fits and I can do a belt drive if I want to. I really want to go left hand drive as it just looks easier but having a hard time deciding and or finding parts. Looking for some that have done it to point me in the right direction. Advantages of right over left hand drive? Left over right hand? Places to get an ACS southpaw freewheel, is it the only one? Are there other parts that would make it easy? I have some posts that will helped marked after hours searching but I am sure there are more.

[MattyCiii]

I really want to go left hand drive as it just looks easier but having a hard time deciding and or finding parts. Looking for some that have done it to point me in the right direction.

With a few hundred miles on my drive, great performance and rock solid reliability (after the first few dummy mistakes I made), here's what I learned about left side RC drive from my folding bike build:
1) Advantage of left drive over right: I still pedal, and love to pedal. Left drive keeps the normal feel and reliability of the standard bike drive. By turning the throttle (on my left handlebar) and listening to the Recumpense V4 drive wind up, I can add the perfect amount of e-power to match my current speed. With a 3210 on 8s and 5:1 reduction, I have the torque to get up a hill, blast away from a standstill, or the finesse to add just a little umph to take the drag off a headwind. I can do this because I set the pedal power through the bike gears separately from the motor pull through the throttle. I can't imagine it being easy to precisely mix leg & e-power with the drive on the right.
2) Parts are not hard to find. The way you have the DaVinci installed, you need to put a standard freewheel on the DaVinci, and a chainring on the rear wheel. FFR Trikes sells a chainring mount that bolts to the disc brake mounts, has 130mm BCD for the chainring. Works out real nice, no need for south paw.

You'll of course need a chain tensioner, which needs a straight and solid mount. I had one mounted with a touch of play. It went a little off kilter on a bump, then got sucked into the chain, sized the rear wheel and took out a spoke. Lucky I was moving real slow at the time.

[recumpence]

Does the drive fit under the downtube? You will have far less chain growth if you can get the freewheel in front of the suspension pivot rather than above it.

Matt

[biohazardman]

Matty
Thanks for the info I was just searching 3220 instead of the 3210 and 3215 as well so now much more info as well as specifics from your build.

Matt
This is the way I had it planned out, in my head, and the frame had the same size downtube as the last so the brackets fit. I do see what you mean about the chain line but was not looking at it in that way. Actually was thinking more on the line of this for a bit more reduction. But I need lots of parts yet.

[recumpence]

Oh, Man, that is awesome!

Matt