Why not comfort bikes?

MikeSSS said:

The Townie has a pedal forward, low seat frame. It has no suspension, the frame is aluminum, the fork is steel. I was thinking of using a Thudbuster long travel seatpost, but there is barely enough room for this seatpost and still having the seat low enough for me to touch feet on both sides when stopped. Pedal forward does not allow standing for bumps, so a suspension seatpost is a must for aging spines. The stock seatpost is rigid. For me: no standing + no suspension = no Townie. Well, never say never.

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All of my bikes are "crank forward". Three are KHS Manhattan Smoothies. One of each size. The middle sized has a short seat tube and easily fits up an NCX seat post. I'd call it a medium sized frame. I can, and often do stand up on my large frame version.
Old photos from 2014.

I do have a Trek Pure flat foot too. The frame Trek was sued over. I have a difficult time standing up on it's pedals, but the large KHS has a very chopper like high handlebar and is easy to stand on.

dogman dan said:

I took the features I needed, and welded a longtail cruiser that is my most comfortable ride to date. Anybody needing special features needs to buy a wire feed welder. If I can weld a frame, so can you. Never took a class in welding, and still weld like a monkey on lsd. But I build what I want out of junk steel frames.

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When I am overwhelmed by the urge, I'm going for brazing. I've done some small stuff that came out OK, putting together pieces of angle iron and bolts and stuff for a handlebar pivot. The brass rod I'm using needs such high temperature that the small work can suffer a bit, but I think bicycle tubes won't be a problem; if it is, could try switching to silver. Seem to vaguely recall that the story back in days of old was that everyone brazed, because welding heated up the tubing so much that the alloy properties were compromised or the geometry was distorted, forget which.

Do you salvage tubing, or buy virgin stuff?

There are two types of brass-style processes. Brazing and braze welding. They are very close.

Brazing depends on very small joints that are very clean. The brass will get sucked into the joint through capillary function. This is what people use for welding custom steel bikes with lugs. The tubing is cleaned and fits tightly into the cast steel lugs and the brazing just provides filler material to effectively 'glue' them together.

Braze Welding uses the brass in a bit more structural way and can be used to form smooth fillet welds and fill gaps. It can be insanely strong. Unlike with soldering the base metals mix together on the surface to form a alloy of both so there is no seam. They effectively become one piece.

Before Tig welding came along this is how people tended to build race cars and airplane frames out of tubing. Nowadays TIG is used. Tig machines are now pretty cheap and it's a well known process.

For metal strength... Nicer quality steel bikes use some form of Chromoly steel. All the popular steels are very close to 4130, just with special trade names to make them sound more exotic. Chromoly steel is extremely strong, much stronger then mild steel.... but only after proper heat treatment. If it's not properly tempered then it's only marginally stronger then mild steel and is absolutely not worth the additional cost.

When people are building high-end custom road bikes they buy tubing that is pre-heat treated and then try not to ruin the tempering when joining the metal. Also one of the reasons why high-end tubing is butted. It's thicker on either end where it gets cut and welded so it'll be stronger in the areas were the tempering is likely compromised and still save a lot of weight.



For easy DIY bike modifications it's probably easiest to just use mild steel and mig welding. Mild steel won't lose it's strength from welding. And mig welding is relatively easy to get right. If you just want to get going then Hi-ten frame bicycle and mig is the way to go. Just need to make sure the welds have good penetration and learn how to cut, tack, manage heat, and brace things correctly so they don't warp.

If somebody is serious about welding the best thing is probably to ignore gas welding techniques nowadays and learn how to stick weld first, then learn mig, then learn tig. If budget is a issue then cheap multi-process tig/stick machines are available all over the place. Dealing with gas processes is a PITA because the only places that handle tank refills are professional places only open during business hours. Taking time off work so you can shop for your hobby is usually a no-go. Were as you can get tig/stick/mig stuff at most hardware stores.

As luck would have it though, it's easiest for me to go for an acetylene refill during business hours, and the local shop is open on Saturday too.

The distinction between brazing and braze welding is interesting, but it isn't clear to me that it's real meaningful. The same filler material with the same melting point, so it seems like the chemistry, or metallurgy if you like, would be about the same. With brass - might be a different matter with silver brazing, don't know if that might just be better suited to capillary brazing and not so much to "braze welding."

I really like it - playing with fire, cleaning off a piece of steel with veins of brass in it where I joined it ... The down side is aluminum, so far anyway not really getting much joy there.

I can just imagine how weak my brazing would be, my welding is a joke.

I start with a bike frame, best I can get hold of, very high quality cro mo. After that, I could be using anything handy to finish out the frame. I have collected a lot of junk frames, always looking for good tube, but I will use electric conduit if I must. Just weld that shit on a windy day, rather than breathe zink. I have also used some freebie half inch square tube.

These bikes don't always turn out light, but I'm after strong in most cases. See my sig links for build threads.

I'm probably not ready to braze up a bicycle yet, but purely beginner non-skill has been good enough for some functional parts. The frame joints would be in large part about getting everything jigged up solid and fitting together, which I suppose is true with welding too. Slightly lower temperature means less destruction, and the joints are plenty strong when the brazing works right. I practiced brazing pieces of angle iron together into a box, and then I'd mash it with a sledge. What I envy a little, aside from the skill to reliably get a good braze, is the ability to build up a brass fillet as I've seen the bicycle builders do in videos.

donn said:

I ride a recumbent with a rear DD hub motor, and it is absolutely fabulous. And it has rear suspension. Even though I don't ride real fast - often less than 15mph! - I ride a lot faster on the average than I did without the motor, and the constant hammering on me and everything on the bicycle was unpleasant at best. I think a suspended [C]LWB recumbent makes an ideal motorized package, for someone who doesn't need to ride like a circus clown (or will develop the skills to do that if it's a requirement.)

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Yah!!

I've tried all kinds of bikes, including recumbents where you nearly lay down flat.

CLWB ( semi recumbent ) perfectly emulates the posture you'd be in while driving a car. What i don't understand is that in our car centric culture, where your average person has sat in a car for thousands of hours over their lifetime, that a bicycle that has the same positioning isn't seen as a holy grail for comfort and straight up riding pleasure - as they're also more faster than an upright.

Here is a fairly tall semi recumbent bike, a maxaraya ray 2, demonstrating the good visibility on the road and carlike posture.





I think a CLWB handles well enough to feel confident going fast. I feel safer doing 30mph on a CLWB than any upright bike i've ever built, because i know it tolerates wobbles and other funky things better due to the low center of gravity. I know that if i dump the bike, fall a shorter distance and road rash is my biggest problem.

I find that mine isn't much less confident at low speeds and in tight situations than a regular bike.
Here is an example of handling that i put together to demonstrate how well my big cannondale ( almost has the wheelbase of a smart car ) handles in tight situations.

[youtube]5Zw-qJcOGpg[/youtube]

When human power is very important, do you actually get as much from that position as when you can stand on the pedals and get all your weight into it?

john61ct said:

When human power is very important, do you actually get as much from that position as when you can stand on the pedals and get all your weight into it?

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Nope, you lose a huge amount of leverage when it comes to going uphill. This is why a recumbent or semi recumbent is best paired with a motor.

What you lose in uphill leverage, you gain in efficiency/speed on flat ground or downhill. I see my motor consuming about 600w-700w to sustain 30mph on crappy tires, whereas an upright bike i'm seeing 1000w to sustain that speed, with the highest efficiency hub, on low friction tires that cost $75 a piece!!

On pedal power alone, i can sustain 17mph indefinitely on my road bike, whereas on my recumbent, i can sustain 20mph. The speed per watt differential just gets larger the faster you go. My BikeE currently has low friction tires on it and i can consistently pass lycra riders, even up slight inclines ( 1% or less ), which is impressive considering i have arthritis in 3 joints :lol:

I can't imagine how much better a full recumbent is, but there's no way in hell i'd ride one in urban traffic.

There's a technique component to this, of course. Recumbent enthusiasts can be a little fanatic about pedaling cadence. You could look at the "stand on it" technique as a way of coping with a gearing mismatch, that of course isn't available to someone in a recumbent position, so in that case you want to keep the gearing matched to the load. That doesn't make climbing easy, and recumbents riding in a group reportedly tend to fall back on the uphill grades - and forge ahead on the downhills. That's why the whole picture changes when you put a motor on them, as neptronix points out.

That said, depending on the shape of the bicycle, it's possible to push against the seat back to some extent, to develop more force. The down side of this maneuver isn't inefficiency so much (using your weight doesn't get you anything you didn't work for), it's just (I think) a potential risk to knees and other joints that aren't built for that particular effort so much.

But ... who cares? My point being, if it's all about cycling efficiency for you, then you should probably stay away from recumbents. They have their pluses and minuses - they're a little more aero, but don't listen to the stories about recumbents being banned in racing because they have an unfair advantage, that's bunk. If that's a big deal, you will probably be bugged by the deficiencies, however the whole picture adds up. The recumbent is for people who want to ride sitting back, period, and they know why they want to ride that way. Usually because it feels a whole lot better after a long ride, maybe because they care about a particular aero improvement, maybe because they like looking up at the sky.

As for "full recumbent", that's a term that I see in the motor simulator but not a commonly observed distinction among available recumbents. It could refer to the Low Racer / High Racer type designs, where your feet are nearly at the level of your head. I think they're nutty, but they're actually fairly popular relative to recumbent designs in general.

donn said:

My point being, if it's all about cycling efficiency for you, then you should probably stay away from recumbents

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Well efficiency is an issue of course, but in my case I need to be ready to finish on human-power only, and on big inclines, contribute as much as possible just to keep the motor from burning out.

> The recumbent is for people who want to ride sitting back, period, and they know why they want to ride that way. Usually because it feels a whole lot better after a long ride, maybe because they care about a particular aero improvement, maybe because they like looking up at the sky.

That's very useful, thanks

john61ct said:

on big inclines, contribute as much as possible just to keep the motor from burning out.

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A semi recumbent will require power while going uphill ( especially at higher speeds ) because of the aerodynamic advantage it has. So you will not necessarily have to pedal harder.

In addition, semi recumbents usually have 20" rear wheels, therefore they can produce more torque and continuous power per lb of hub motor you throw at them, versus say a typical 26" wheel. :thumb:
If we're talking about a mid drive, then unfortunately you don't get an advantage there.

Also, because of the 33% reduction in needed power, your motor will be a lot cooler before you start going up the incline. So you will have a head start on the whole overheating issue.

20" wheels have huge power advantages with hubs and recumbents have aerodynamic advantages.
And you can fit scooter/moto/moped tires to 20" bicycle wheels and have a LOT less worries about flat tires.
It's a sweet combo of attributes

I've been building uprights until a year ago. There is no way in hell i'll go back for the above reasons... and comfort too

I thought there was an advantage for more torque on a smaller wheel dia on mid drives.
But hey, your more then likely right!

neptronix said:

If we're talking about a mid drive, then unfortunately you don't get an advantage there.

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I have a 2009 Giant Cypress with a Bionx 350W lot installed.
I sit upright, very comfy.

neptronix said:

john61ct said:

on big inclines, contribute as much as possible just to keep the motor from burning out.

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A semi recumbent will require power while going uphill ( especially at higher speeds ) because of the aerodynamic advantage it has. So you will not necessarily have to pedal harder.

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No, pedalling harder is not just required on steep hills - with low speed, heavy loads and no gearing - but I actually **want** to contribute as much as possible when the motor is straining at high amps.

The other factors in my use case are mostly dirt tracks, paved roads rarely, need big fatties for getting over the ruts sticks & stones as smoothly as possible

and also generally very low speeds, so slipstreaming much less beneficial.

We seem to be talking about different things here. There is no significant aero advantage at up-hill pedaling speed, and overall, relative to an upright design, the only question is how big the disadvantage is going to be (and whether it matters.) They're open road bikes, not mountain bikes.

Mine has a 26 inch rear wheel, by the way, and still probably qualifies as a CLWB (Compact Long WheelBase.) I expect the difference in the ride however is more that mine steers via a linkage connected to the forks, rather than directly turning the forks on a long handlebar stem. That allows the forks to be a in more normal near-upright angle, while the steering can be whatever works for the rider. (I've moved mine from above the seat as originally designed, to below the seat as in classic recumbents like the Avatar 2000.) On a CLWB, you're close enough to the front wheel to more or less avoid a "tiller" effect with that long stem, but with direct steering it's what it has to be, whether optimal or not, and there's going to be a little "wheel flop".

The comfort bikes are great for electric conversion.

https://www.trekbikes.com/au/en_AU/bikes/hybrid-bikes/urban-commuter-bikes/c/B440/
You will notice on some of the more modern Trek "Hybrid/Dual-sport/Comfort" bikes over the last 4 years they have deliberately made the back frame area wider to allow for extra-wide tyres...


For a lot of older Hybrid bikes, you could NOT fit your finger between the back fork and the tyres even if it was a pretty skinny tire, but the newer ones are much wider.
The ability to add wide tyres also allows for anyone to build their own back hub motor wheel and not worry about perfect dishing. To me I think the designers secretly had this as part of the design idea.
https://trek.scene7.com/is/image/TrekBicycleProducts/DS2_19_23067_B_Alt8?$responsive-pjpg$&wid=960&hei=710


Trek has been pimping/implementing their "massive tyre clearance" on all their modern bike models, except of course the classic road bike designs
https://www.trekbikes.com/au/en_AU/plus_sized_tires/

markz said:

I thought there was an advantage for more torque on a smaller wheel dia on mid drives.
But hey, your more then likely right!

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On a mid drive, you can change these things by regearing one of it's initial reductions and then increasing the volts. It's like tuning a gasoline engine to spin faster and thus making more horsepower out of it.

Then you can adjust the bike's gearing for higher speed, less torque, or lower speed, more torque etc.

So in a mid drive, you don't have to change the wheel size to optimize anything. The gears do that job.

In a hub motor setup, you only have one adjustment, and that's wheel size. Most hub motors in a 26" wheel are not optimized for power, and can make more power and higher efficiency by going to a smaller wheel. For example, the "MXUS 3kW" DD hub makes a legitimate 3kw continuous in a 20" wheel. Put it in a 26" wheel and we're talking more like 2.2kw continuous in reality. This is the difference of spinning the motor effectively 26% faster per mph.

Whereas a geared motor may actually lose continuous power/efficiency when spun fast because the gears inside incur a greater friction penalty at all times. However, they will make a shit ton of extra torque potential, of course.

Most semi recumbent bikes have 20" wheels, or you can change the wheel size without worrying about the pedals smacking the ground, unlike uprights. You can also pull off this trick on upright comfort bikes much easier, as the BB is forward and up moreso than on a traditional upright :thumb:

This applies to DD hubs only right?

Geared hubs are generally less raw power, but are there exceptions?

Ability to shed heat becomes critical too, when climbing steep hills with heavy loads.

My thinking is multiple motors. . .

Right, and I think the geared hub's down side is really more that heat issue, than efficiency lost in the gearing - I mean, that's where the heat comes from, but the direct drives are mainly just better at shedding it. So the geared hubs tend to zero in on a balance between small and powerful, where the direct drive doesn't really know any limit. Some day there will be an external variable gearing solution that 1) doesn't piggyback on the intended-for-radically-less-power bicycle drivetrain, and 2) doesn't share the motor enclosure, so less overheating potential. I guess that might start getting some attention when the electric bicycle world gets out from under the spell of the electric vehicle crowd.

To reply to both of you..

Yeah, a DD motor can take the abuse for longer periods of time, for sure. It also responds to a small wheel better. The best geared hub hits something like an 84% peak efficiency whereas a DD hub of the same continuous wattage can be up to 90%. Add the 6% efficiency differential to the geared motor + it's inability to shed heat and the case for the geared motor starts to look more limited..

I still like geared motors like the MAC and Bafang G310 with it's dual reductions.. the benefit will be seen if you have stairs to hike your bike up, or when you have to pull the wheel off to change a tube in the middle of summer or winter. They're also ideal for lower power requirements, IE 25-30mph.

It all depends on what you're looking for. I tend to use the ebikes.ca motor simulator as my guide for this.

donn said:

Right, and I think the geared hub's down side is really more that heat issue, than efficiency lost in the gearing - I mean, that's where the heat comes from, but the direct drives are mainly just better at shedding it

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I think the ability to derate current based on overtemp is critical.

By default I consider CA v3 to be the exemplar, but apparently some high-functioning controllers have that built in, dunno if as adjustable, suggestions welcome.

I need 3-4000W minimum, so most geared options are out, suggestions welcome.

an external variable gearing solution that 1) doesn't piggyback on the intended-for-radically-less-power bicycle drivetrain

Yes a high power hub motor with a built-in Rohloff Speedhub that can handle, what 200+ Nm? would be nice.

Only needs 3-4 gears too, not 14

neptronix said:

best geared hub hits something like an 84% peak efficiency whereas a DD hub of the same continuous wattage can be up to 90%
…
lower power requirements, IE 25-30mph

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Well efficiency is great for range at cruising speed or mild inclines.

My critical need is for super high torque, high power when going slow.

Those speeds are faster than I ever need to go, even a 20mph top would be fine, maybe most-efficient cruising on flat macadam at 12-16mph. . .

Steep climbing with a heavy load might only be a brief percentage of the ride, so efficiency at that time can go out the window,

the problem is can the motor even do the job at a low enough speed and survive?

That's why thinking combining say

strongest available drivetrain + mid-hub (Bafang G310 is it?), **and**

a MAC (Grin version?)

for standing starts, both optimized for getting up to (say) 8mph and those steepest hilly bits

And then (maybe? crazy?) a straight DD for the "normal wear & tear" cruising 12-16mph. . .

In an extreme load+incline crisis, seeing if it helps to activate all three.

Yes I know I need a battery pack weighing more than most full kits

john61ct said:

I think the ability to derate current based on overtemp is critical.

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That's why i use the ebikes.ca sim to figure this out. Any powertrain i design has to sustain 7% grades for quite a few miles. They are always oversized and thus run in a high efficiency spot in the powerband.
Oversize it too much and you have iron losses eating away at your efficiency on the flats. And more weight than you need.

I have a lot of room to play with because i only build bikes with 22" wheels or smaller these days. The comfort bike platform is perfect for this, because you can extract more efficiency and power out of any DD hub, which also translates to better thermal management of course :thumb:

john61ct said:

By default I consider CA v3 to be the exemplar, but apparently some high-functioning controllers have that built in, dunno if as adjustable, suggestions welcome.

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The CA v3's thermal throttling should be considered a 'save your ass' option and not a way to increase your thermal overhead. Consider that you're going up a hill and the power delivered keeps dropping.. you drop into lower and lower RPMs, and the efficiency exponentially goes down the closer you get to 0rpm. An unfortunate characteristic of electric motors.

john61ct said:

strongest available drivetrain + mid-hub (Bafang G310 is it?), **and**
a MAC (Grin version?)

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This would be a lot heavier, far more expensive, less efficient ( overall ), and more of a maintenance problem for you down the line, versus a single DD hub.

Check this out. This is a 30mm wide DD ( 14-15lbs ) in a 20" wheel in a semi recumbent frame going up a 10% grade for 11 minutes straight. That's a pretty hardcore climb, and probably beyond what you're trying to do. You can play with the parameters in the simulator from this link and see how she runs on the flats, lesser hills, etc.

https://www.ebikes.ca/tools/simulat...cust_60_180_0.03_V&axis=mph&blue=Lbs&grade=10

20" CLWB semi recumbents allow us to pull stunts like this. Can't do this on an upright bike because 20" wheels + fits a full size adult generally isn't happening unless you have some oddball chopper frame without suspension, and you're gonna regret not having suspension.. so..

Now if we switch to a 26" wheel, MTB frame, and a slower winding to make up for the wheel size difference, look what happens with the same motor. It chokes in 5 minutes.

https://www.ebikes.ca/tools/simulat...cust_60_180_0.03_V&axis=mph&blue=Lbs&grade=10

That's the small wheel and aero advantage of a semi recumbent.

a 24" rear wheel would be a nice compromise on a crank forward 'comfort bike', but It's just not as good.. and you rarely see rear suspension on those kinds of bikes, which you really need, since more of the weight sits on the back of the bike than usual.

There is another "comfort bike " on the market. It can be purchased either pedal powered, or electric assist. The Day 6 --https://day6bikes.com/