serious_sam
10 kW
Hello. I’m looking to put an electric bicycle together over the next couple of months, and was hoping to get some feedback. Once I get hold of some parts, I will document the build.
[EDIT] Change of plan. I was planning on building a bike for commuting, but my work circumstances have changed, so now I will build a bike for off road instead [/EDIT]
I won't have any problems putting the bike together, I'm an engineer with plenty of experience with mechanical and electrical systems. But since I have no experience with electric bicycles specifically, I'd like some constructive criticism on my selection of components.
This is my plan so far:
https://www.ebikes.ca/tools/simulat...h&k=1&frame=mountain&autothrot=true&throt=100
(The motor simulator has got to be one of the best tools on the web. Thanks to the geniuses at Grin Tech. You rock).
Donor bike:
A downhill mountain bike, around 5-10 years old. I’m currently looking at a Norco Atomik or Norco A-line. The A-line has bolt-on dropouts, which I imagine will make modifications for mounting the motor much easier. It appears that downhill bikes are well suited because they are quite robust (suited to withstanding higher torques), and have better stiffness and geometry for higher speeds.
Dropouts:
I will design some clamping style mounts that could bolt onto (or in place of) the original bike dropouts. Machined in 7075-T6, or 4140 steel as an alternative.
I understand dropout/clamp material is a contentious issue. The upside of the 7075 is the lower cost to machine, and better appearance of anodising (relative to painted or rusty steel). The downside is the significantly lower modulus. Even though it has a slightly higher hardness than mild steel, deflection at the contact surfaces under high load can cause fretting and possibly yielding. I can see this compounding into a real problem when running regen. However, if I can get the clamping arrangement just right, it might be ok. I think this is the highest risk component, so I will do some analysis in this area to justify the decision either way.
Motor:
MXUS 3k v3 4T. I figure the 4T will give me a good compromise between speed and heat output. I will add FF (but no heat-sinks, at least at this stage). I will try to set a current limit so torque is limited to 200Nm. I think this is a realistic safe target for a bicycle.
Wheels:
Go to 24" motorbike rims. Either redrill the hub flanges to suit 14G spokes, or use brass washers and the original spoke holes. Not sure yet.
Gearing:
Single speed freewheel. Not much point havnig gears if I am going to rely on power 100% of the time. Pedalling a DH bike is hard at the best of times. I'd rather not do it with a 10kg hub and 5kg battery pack.
Battery pack:
20S5P of Sony US18650-VTC6. Actually, 2x 10S5P in series, each with its own BMS. That way I can charge them in parallel using a Meanwell HLG-320H-48A. Originally I wanted to run 24S, but the controller I was also planning on using is limited to 88.8v. The total weight should be around 5kg, and I will put it in a back pack. If the frame had a bigger triangle, I would think about frame mounting them, but I don’t see it as a big issue. Time will tell.
Controller:
I was looking at the Mobipus 72200. I like the industrial style construction, and from what I’ve read, it is relatively user friendly. The only problem is supply. I have tried to get in contact with SamD from Ballarat Ebikes, but he has only responded once to my emails (he only asked where I am located). I responded to him. Then no response back. His website is still operational, and advertising parts. Does anyone know if this is normal for him, or has anyone been in contact with him lately ?
So, I am kind of at a loss for what controller to use. Does anyone know of a comparable power level controller that is available in Australia ? It is costly to ship to Australia, so I would prefer to buy locally if possible ? But that might really limit my options.
Anyway, that’s the current plan. If anyone has any suggestions, I’d be thankful for your words of wisdom. Cheers.
[EDIT] Change of plan. I was planning on building a bike for commuting, but my work circumstances have changed, so now I will build a bike for off road instead [/EDIT]
I won't have any problems putting the bike together, I'm an engineer with plenty of experience with mechanical and electrical systems. But since I have no experience with electric bicycles specifically, I'd like some constructive criticism on my selection of components.
This is my plan so far:
https://www.ebikes.ca/tools/simulat...h&k=1&frame=mountain&autothrot=true&throt=100
(The motor simulator has got to be one of the best tools on the web. Thanks to the geniuses at Grin Tech. You rock).
Donor bike:
A downhill mountain bike, around 5-10 years old. I’m currently looking at a Norco Atomik or Norco A-line. The A-line has bolt-on dropouts, which I imagine will make modifications for mounting the motor much easier. It appears that downhill bikes are well suited because they are quite robust (suited to withstanding higher torques), and have better stiffness and geometry for higher speeds.
Dropouts:
I will design some clamping style mounts that could bolt onto (or in place of) the original bike dropouts. Machined in 7075-T6, or 4140 steel as an alternative.
I understand dropout/clamp material is a contentious issue. The upside of the 7075 is the lower cost to machine, and better appearance of anodising (relative to painted or rusty steel). The downside is the significantly lower modulus. Even though it has a slightly higher hardness than mild steel, deflection at the contact surfaces under high load can cause fretting and possibly yielding. I can see this compounding into a real problem when running regen. However, if I can get the clamping arrangement just right, it might be ok. I think this is the highest risk component, so I will do some analysis in this area to justify the decision either way.
Motor:
MXUS 3k v3 4T. I figure the 4T will give me a good compromise between speed and heat output. I will add FF (but no heat-sinks, at least at this stage). I will try to set a current limit so torque is limited to 200Nm. I think this is a realistic safe target for a bicycle.
Wheels:
Go to 24" motorbike rims. Either redrill the hub flanges to suit 14G spokes, or use brass washers and the original spoke holes. Not sure yet.
Gearing:
Single speed freewheel. Not much point havnig gears if I am going to rely on power 100% of the time. Pedalling a DH bike is hard at the best of times. I'd rather not do it with a 10kg hub and 5kg battery pack.
Battery pack:
20S5P of Sony US18650-VTC6. Actually, 2x 10S5P in series, each with its own BMS. That way I can charge them in parallel using a Meanwell HLG-320H-48A. Originally I wanted to run 24S, but the controller I was also planning on using is limited to 88.8v. The total weight should be around 5kg, and I will put it in a back pack. If the frame had a bigger triangle, I would think about frame mounting them, but I don’t see it as a big issue. Time will tell.
Controller:
I was looking at the Mobipus 72200. I like the industrial style construction, and from what I’ve read, it is relatively user friendly. The only problem is supply. I have tried to get in contact with SamD from Ballarat Ebikes, but he has only responded once to my emails (he only asked where I am located). I responded to him. Then no response back. His website is still operational, and advertising parts. Does anyone know if this is normal for him, or has anyone been in contact with him lately ?
So, I am kind of at a loss for what controller to use. Does anyone know of a comparable power level controller that is available in Australia ? It is costly to ship to Australia, so I would prefer to buy locally if possible ? But that might really limit my options.
Anyway, that’s the current plan. If anyone has any suggestions, I’d be thankful for your words of wisdom. Cheers.