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Hunting E-Bike build - broken frame rebuild

engineerjoe

engineerjoe

Enginerd
Joined
May 20, 2020
Member Number
709
Messages
57
Loc
CO
I have an addiction to mountain bikes. If I could, I would buy thousands of dollars of bikes and parts. But I can't, so I build what I want in my garage with a vise, hacksaw, files, home-built frame jig and a welder. I build frames as a hobby for myself, and for people who have been a big part of my life.

This will be my 7th frame, and it's for my Dad. He has been interested in a pedal assist e-bike for a while, mostly as a way to get to treestands during hunting season. Quiet, no exhaust, easy to lift over a fence if needed, and easy to use. He wants a bow/rifle rack on it too (might double as a golf bag rack)

Being a cheap-ass, I watch the local online ads for bikes with broken frames, or strange sizing, that make them super cheap. Then I buy them for the parts, and build a new frame that fits. This build is no different.

I found a medium 2015 Haibike Sduro E-bike with a broken front triangle for $750. If you look in the pics you can see the repair on the seat tube. The previous owner said it was re-welded, and he added some fiberglass wrap to strengthen it. It would probably hold just fine as is for bike path riding, but probably not offroad, and definitely not being used by my dad (he's pretty hard on stuff).


20200515_090442.jpg



After I got everything disassembled, I measured the motor mounting holes and suspension mounting locations. I took it in to work and measured it on an optical comparator to get the locations a little more exact than what I could do with a straight-edge and calipers. With all that info, I started putting it in CAD. I had a good idea of the geometry I wanted, but fitting the motor in and around the tubing took a little time.

Hai-1.png

hai-2.png

geo-Haibike.png


First thing was to cut some parts on the laser at work out of .120" cromo and see how close my measurements were.

20200909_194731.jpg


Fits pretty good!! I'll clearance a few spots and start the welding this weekend.

20200515_090442.jpg


geo-Haibike.png
 
Anybody have a good idea for the bow/rifle/golf bag holder? I was thinking offset, behind the seat. Thoughts?
 
engineerjoe said:
Anybody have a good idea for the bow/rifle/golf bag holder? I was thinking offset, behind the seat. Thoughts?
Click to expand...

Nope. Not a single useful think i will be able to bring to this thread. :flipoff2: I am stoked to watch it though, it looks awesome.
 
Oops...

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I never claimed to be a welder. My angle was a little off and I couldn't see what I was doing.

I am getting better at filling holes though.

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And put it in the frame jig
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20200912_161133.jpg
 
This is how I cut miter (mitre) joints.

I take my 2D drawing and get the diameters and the angles between the tubes and put it in this calculator:

https://dogfeatherdesign.com/ttn_js/

Print out the templates and cut them out.
20200912_191947.jpg



Put a straight line down the length of the tube to align the two ends and tape the template on the tube
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Sharpie the end of the paper to make a line to follow

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take off the template and cut as close as possible with a hacksaw

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Squamch said:
Holy shit. You should look into this tool called an "angle grinder." It might change your life.
Click to expand...

gozuki said:
Harbor freight has a tubing notcher for under $60 too...
Click to expand...

I have one. It's not quite precise enough for me, and buying multiple hole saws that are straight and the dia I need are $$$.

I make about 2-3 frames a year. That's a total of 10-15 miter cuts on thin wall tubing (0.9mm or .035"). Using a grinder or notcher would have to be cleaned up with a file anyway. If I was doing more miters, or thicker material, or just one size of tubing, it would make sense.
 
I know it's probably too late now but is that burnt tube going to be a weak spot on the future? I would have thought you would want to replace it when there was not much attached. For the rack I think above the back tire right behind the rider would give the best balance during off road riding. When I lived around the beach surf board racks were mounted behind the tire many times and you could definitely feel them a lot while riding. Lower beside the tire would be less top heavy but would probably snag on things. Front mounted may be a good option depending on the terrain.
 
I like the idea and have been kicking around an idea for a similar project. I only really go turkey hunting and and use my mtn bike to cover some ground. After the shot I pretty much just tie the bird to my backpack and carry it that way. But some buddies of mine got in a club for some pig hunts and I would need a different set up.to pack out big game.

For my application I was thinking of pulling a single wheel trailer behind the mtn bike. Debating if I want to built it to haul whole animal or process animal in the field and pack meat into a cooler.

Just a suggestion to some small accessories to add to your frame - a gun rack. across handlebars is too wide, slung across your back is awkward. I think having the rifle basically in line with the top tube and muzzle pointing out the front would be ideal. One more thing is a chain guard - hunting clothing is loose fitting and i cant tell you how many times I got my pants hung up on front chain ring. Maybe a light plastic or fiberglass peice - just something to keep the pant leg out
 
Here is my setup, Sur Ron 6000w electric motorcycle with a Burley trailer. I've added bigger/better tires to both units, geared down the bike and converted the primary belt drive to a chain drive. I also have a peddle conversion for it. Went from 47mph top speed to 40 but it rips on the trails. I was hunting a single track trail a few weeks ago and it had a bunch of downed trees across it. At 110-120 lbs its not hard to lift the bike over them. I pack my gun on my back while hunting on it.

This is my brother putting around when we got back to camp with his muzzleloader buck this year.

https://www.youtube.com/watch?v=09kPK9RFAT0
 
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