GoFastGus
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I'll take a look at those for fork options, thanks!
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Effects of Changing a Fork on Suspension Geometry
- Thread starter GoFastGus
- Start date
GoFastGus
⚡ Regular
Most buses around here are like this, the bigger routes have bike storage inside the bus. No weight estimates yet, but given how hard it was to wrangle the last project onto the cow catchers, this one would probably be even worse.
Gotcha. My guess was that a 26x4 tire would have a larger contact patch than a 27.5x2.5 tire, but I don't have a formula to calculate contact patch size.
Exactly why I've been looking for semi-slicks. 27.5x2.5" Hookworms were my previous pick, and if I end up going the full suspension route instead, that's what I'll do.
For sure! Lockup means losing control over steering inputs, not to mention excess tire wear.
Supposedly they're fixing this soon. The problem is that the interface between the torque arm and the motor isn't up to par with what the motor could actually dish out. So the only way to run it today is to power limit it.
Some recent back-story:
https://endless-sphere.com/sphere/threads/salsa-blackborow-with-grin-max45.128509/page-3
GoFastGus
⚡ Regular
ZeroEm
🏍️ Giga poster
Keep this in mind, most of the time lower voltages makes slower bikes that do not push as much wind. pushing wind is what it's all about. Smaller wheels are more efferent but make for a bumpy ride.
Everything has it's plus and minus. You will just need to find what you want most. You want to ride all the way to work or go fast. The closer to 20 mph you ride the farther you can go. Fit the most battery and then see how fast you can go and still make it. You don't need to make a week bike just keep the speed down until you need it.
Everything has it's plus and minus. You will just need to find what you want most. You want to ride all the way to work or go fast. The closer to 20 mph you ride the farther you can go. Fit the most battery and then see how fast you can go and still make it. You don't need to make a week bike just keep the speed down until you need it.
That's the other thing about high speeds...it takes a LOT more power to go 50mph than say, 25mph. Much more than twice the power.
A random googlefind chart on this page, which I can say for sure is not correct in the particulars, as it takes a lot mroe than 178w to go 20mph on a typical ebike-shaped object (and something less aero like my trike takes around 800-1000) but the proportions might be close. You can use the simulator at ebikes.ca to see for your conditions and potential equipment what it will take at various speeds.
https://www.happyrunsports.com/blogs/electric-motorcycle/how-many-watts-are-needed-to-achieve-50-mph
Chart: Watts Required at Different Speeds
| Speed (mph) | Required Watts |
| 20 | 178 |
| 30 | 400 |
| 40 | 711 |
| 50 | 1,111 |
What it comes down to is that you need a battery tha'ts up to several times the capacity for 50mph vs 25, to give you the same range.
It might only have to be twice as big for 50 vs 35.
That's just talking about capacity; not bringing up performance (current capability vs voltage sag etc). It probably has to be bigger just for that, using cheaper parts.
Check out the simulator at ebikes.ca to give yourself an idea of what's needed.
GoFastGus
⚡ Regular
Voltage and wheel size are still up for debate, so I'll have to consider those, thanks!
My biggest debate about the direction of this build. Going for lighter weight and more charge capacity or speed at the cost of weight and capacity?
This frame can fit about 120 21700 cells. I'll need to make a post about everything I'm planning for this bike atp.
GoFastGus
⚡ Regular
Drag increases with speed squared according to XKCD's What If?, so I'd expect it would take 4 times the power required to go 25mph in order to go 50mph, assuming no other extra sources of resistance.
I should have splurged on a controller that I could have datalogged with on my last bike. When I was riding it, I was using voltage and speed at a given power setting to gauge motor load. Of course, just having a mental understanding of what load looks like in your specific setup isn't helpful compared to quantitative data that you can review on your computer. I'll try to scrounge up some accurate data to make an educated guess on required power.
I haven't decided on the exact specs of my battery, and cell performance is something I need to dive into more.What it comes down to is that you need a battery tha'ts up to several times the capacity for 50mph vs 25, to give you the same range.
It might only have to be twice as big for 50 vs 35.
That's just talking about capacity; not bringing up performance (current capability vs voltage sag etc). It probably has to be bigger just for that, using cheaper parts.
Thanks for the rec!
GoFastGus
⚡ Regular
Before I completely write off a fat bike build, I want to get people's feedback on a couple things:
If I go the fat bike route, a dual crown fork seems necessary. I have a few options that way:
1. Getting a used DH fork for ~$400. My bike has a 1-1/8" (I think straight, I haven't taken it apart) steerer tube, which would let me fit a majority of forks of this design. I would need to buy a 26" mtb wheel with a 20x110 through-axle and probably run a 26x2.5" Hookworm in the front. The Axle to Crown length would work with something like a Marzocchi Bomber 66 or 888 or a Fox 40. This is probably the cheapest option if I went the fat bike route.
2. I could get a fork for an electric dirt bike (Surron, Talaria, etc.). These could be cheaper if I got one used. They could be similar quality for a better deal, or they could be a turd. They're theoretically designed for more weight and power though, so maybe a well-regarded aftermarket brand fork could be a good deal used. Same problem of 20x110 thru-axle requiring a new wheel. Also not as confident on axle to crown lengths, but what I've seen says they're like 100+mm longer at full droop, so likely several fewer degrees of headtube angle. At this point, pedal brackets would probably scrape and the bike's geometry would be seriously changed.
3. I could get a single crown suspension fatbike fork and convert it to dual crown. Forks like the Rockshox Bluto or the Manitou Mastodon would work great for me, the issue is finding a dual crown kit that keeps the fatbike width for the shocks. I haven't been able to find anything as of yet that explicitly said it would allow continued use of a 15x150mm axle, but I'll have to keep looking. If nothing exists this way, I suppose CNCing a dual crown kit could work, but the time and effort involved just doesn't make much sense.
Evaluating these options compared to a full suspension bike:
If I go the fat bike route, a dual crown fork seems necessary. I have a few options that way:
1. Getting a used DH fork for ~$400. My bike has a 1-1/8" (I think straight, I haven't taken it apart) steerer tube, which would let me fit a majority of forks of this design. I would need to buy a 26" mtb wheel with a 20x110 through-axle and probably run a 26x2.5" Hookworm in the front. The Axle to Crown length would work with something like a Marzocchi Bomber 66 or 888 or a Fox 40. This is probably the cheapest option if I went the fat bike route.
2. I could get a fork for an electric dirt bike (Surron, Talaria, etc.). These could be cheaper if I got one used. They could be similar quality for a better deal, or they could be a turd. They're theoretically designed for more weight and power though, so maybe a well-regarded aftermarket brand fork could be a good deal used. Same problem of 20x110 thru-axle requiring a new wheel. Also not as confident on axle to crown lengths, but what I've seen says they're like 100+mm longer at full droop, so likely several fewer degrees of headtube angle. At this point, pedal brackets would probably scrape and the bike's geometry would be seriously changed.
3. I could get a single crown suspension fatbike fork and convert it to dual crown. Forks like the Rockshox Bluto or the Manitou Mastodon would work great for me, the issue is finding a dual crown kit that keeps the fatbike width for the shocks. I haven't been able to find anything as of yet that explicitly said it would allow continued use of a 15x150mm axle, but I'll have to keep looking. If nothing exists this way, I suppose CNCing a dual crown kit could work, but the time and effort involved just doesn't make much sense.
Evaluating these options compared to a full suspension bike:
- I paid $600 for this fat bike. I have my eye on a 2010 Trek Remedy with a few aftermarket goodies asking $750. If I sell this bike and get something close to my money back, the difference between the two bikes could be within the cost of a new front wheel.
- The finances might make more sense if I just buy an FS frame ($150-300), knowing I want a different fork, an upgraded shock, and probably don't need the drivetrain. That would still leave me on the hook for a front wheel, though, but I might have to get one anyway depending on what wheel the Trek has.
- The steering tire is almost certainly gonna be a hookworm regardless of the frame, so not much sense in trading rear tire width for suspension
- The suspension bike route is a little more straightforward, even if it might be more expensive up front.
What is the attraction of fat tire for you?
Fat tire is really only beneficial for deep mud, snow, or sand. No real benefit on pavement. Actually a detraction in terms of handling.
Of course, it looks like it is better. Apparently (based on fatbike popularity) appearances count a lot. Depends on priorities.
Fat tire is really only beneficial for deep mud, snow, or sand. No real benefit on pavement. Actually a detraction in terms of handling.
Of course, it looks like it is better. Apparently (based on fatbike popularity) appearances count a lot. Depends on priorities.
GoFastGus
⚡ Regular
I don't have a good answer besides being young, stupid, and not wanting to pay the monthly gas, insurance, and parking bills of a motorcycle. I try to be safe with things like full body protection and good suspension and brakes, but I'll be the first to admit I'm learning as I go.
GoFastGus
⚡ Regular
Being able to fit wider tires, which theoretically means more traction, which could aid in stopping.
Yeah, the tradeoff in handling as compared to an FS mtb seems like a more and more poor decision with hindsight.
Couldn't care too much about looks, just going fast (reasonably safely). If there's a better pick for that, I'll sell the fat bike and take it.
fat tires have much higher rolling resistance, can have quite funky steering due to low tire pressure, and also attract cops if they are going fast because they look like a motorcycle without a license plate from the POV of law enforcement.
I would only build such a thing, and keep it to close to legal ebike speeds, if you have a lot of snow to get through.
I would only build such a thing, and keep it to close to legal ebike speeds, if you have a lot of snow to get through.
I built my CBoardman framed e-bike using a NOS 26" full suspension frame, the frame has pretty standard head stock angles etc etc, so to slacken the head stock angle I when for a mullet setup with 27.5" front forks and front wheel, have ridden thousands of miles now and it suits me just fine. Did buy an offset bush for the rear shock but have not fitted it. Also did a similar job on CBoardman hard tail frame again NOS and a similar year frame. The last bike is another CBoardman frame but a secondhand MTR 8.6 29er bought like the others off Ebay, the picture shows it as a 29"f 27.5"r mullet, frame a couple of years old so has a slacker head stock angle, did not suit a mullet configuration so now 29" rear wheel along with a modified Rockshox 35 140 mm and a Rockshox 130 mm Deluxe R.
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Nix Liou
⚡ Regular
Something seems a little off with this chart...That's the other thing about high speeds...it takes a LOT more power to go 50mph than say, 25mph. Much more than twice the power.
A random googlefind chart on this page, which I can say for sure is not correct in the particulars, as it takes a lot mroe than 178w to go 20mph on a typical ebike-shaped object (and something less aero like my trike takes around 800-1000) but the proportions might be close. You can use the simulator at ebikes.ca to see for your conditions and potential equipment what it will take at various speeds.
https://www.happyrunsports.com/blogs/electric-motorcycle/how-many-watts-are-needed-to-achieve-50-mph
Chart: Watts Required at Different Speeds
Speed (mph) Required Watts 20 178 30 400 40 711 50 1,111
What it comes down to is that you need a battery tha'ts up to several times the capacity for 50mph vs 25, to give you the same range.
It might only have to be twice as big for 50 vs 35.
That's just talking about capacity; not bringing up performance (current capability vs voltage sag etc). It probably has to be bigger just for that, using cheaper parts.
Check out the simulator at ebikes.ca to give yourself an idea of what's needed.
On my commuter I can get going about 25mph with 500w, and 400w would not get me to 30. I'm running 1.95 inch Marathon tires, and it's a pretty lightweight build.
I usually hear from people that a 3000w motor is required to go 50 mph, and 1,111 watts for 50 mph seems very low. Here is a bike calculator website that allows you to specify a lot of parameters, though it's not in the context of an ebike but a normal bike.
@GoFastGus I saw in your other thread that you were considering a 20s6p layout of Samsung 50S cells to power the QS205. Whatever option of motor you go with, if you are aiming for 3000w, I would probably not recommend the 50S, just because it has poor degradation characteristics when fully charged (hence some pretty abysmal cycle life numbers for full depth of discharge, ie 250 cycles in some tests). There's better options available now and the 50S isn't cheap enough to justify that tradeoff imo.
Yes, I noted that it isn't correct in the post you'd quoted.
It's proportions seem in the right range but the values themselves are wrong.ebikes.ca motor simulator is going to be a lot more relevant:
Motor Simulator - Tools
Motor Simulator - Tools
GoFastGus
⚡ Regular
1. Very true, I've definitely felt it with pedal power. 2. I noticed the heavier steering the first time I ever rode a fat bike. It's weird, but eventually you do get used to it. I mostly steer by leaning though, only a few degrees with the fork. 3. Good point. The cops around here are pretty bike friendly but no sense trying to find the one who isn't.
I mean we get some snow here in Madison (less in recent years, but that's besides the point), but the roads and trails are well maintained enough to not warrant fat tires as opposed to mtb width snow tires.
GoFastGus
⚡ Regular
Thanks for the advice! I'll do some more reading about cycle life and cell degredation. I'm looking for a 21700 cell with at least 25A max discharge, 5Ah capacity, and good cycle life. I'll look for some good options on that.
Nix Liou
⚡ Regular
Especially at these higher discharge rates, definitely consider tabless cells. They're just starting to hit the market for full scale production (reliance RS50) or will in December or January (Tenpower 50XG, EVE 50PL). Hard to get right now, but that should improve.
The three I mentioned above all perform very similarly, but there's more data on the 50PL. It's rated for 50A continuous discharge (125A temp limited), and Padja has done cycle life testing on it, where it survived 1000 cycles with about 85% capacity, at 20A discharge 4.2-2.5V iirc.
I'm able to get my hands on the preproduction ones for about as much as the 50S, when I buy in bulk (520pcs barely counts as bulk tbh...). I'm thinking about doing a group buy for them in January, when they are officially released.
Reads to me,.. you intend to 'attempt' to fly-under-the-radar,.. with a bicycle that looks like it's in its third trimester, no plate, and you wearing full leathers? Do you honestly believe LEOs are oblivious to such stunts? Having your pride&joy potentially confiscated would undoubtedly be a far more costly "learning" experience than proper registration and insurance.
GoFastGus
⚡ Regular
I'll take a look at some tabless cells, thanks!
I'm reading Padja's cell tests rn, thanks for the rec!
I'll keep an eye out for that, I'd most likely be interested if the prices were competitive with the 50S.
GoFastGus
⚡ Regular
From my experience, Madison is a pretty bike-friendly town. I didn't attracted the cops' attention with my previous build, but I also tried to play it safe on busier city streets and around campus. That being said, it only takes 1 cop who sees me going too fast to put that all to an end.
Yeah that's my biggest fear next to it being stolen. Looking into registration and insurance as a moped or motorbike might not be a bad idea.
Nix Liou
⚡ Regular
The price will hopefully be fairly competitive with the 50S now, but the 50S might drop in price at the same time.
