BMX to MBB recumbent conversion

[Anonymous]

Hi all, got a new bike in the works, put the business end of it together today with my BMX.

What i did was cut the stays and bb from a donor frame and weld a piece of handlebar between the stays. With that clamped into the stem, i added the piece that bolts to the fork crown through the hole. All it really needs now is to swap the cranks to the new bb, slap a chain on it, make it steer somehow, and slap a seat on it. Whee!



I was going to build one of these last week but i was lazy, so here it is this week.

The geometry is all just arbitrary, i just used whatever length the stays and the sqaure scrap was, while getting the bb reasonably low. I'm going to try it with pedal power at first and if the geometry seems right and the style of bike fits me,then i'll motorize it. I plan to build several other styles of recumbent to find something i like, and to get experience with how they feel in different configurations.

Does anyone here have a motorized MBB? If this thing feels good to me i'll probably power the rear with a hub motor and the front with pedal for a 2wd machine.

 

[Anonymous]

Well, i pretty much got it together aside from a seat, some sort of bars, and brakes.



I've got some 990 brakes i could toss on the rear, but they really suck so i'm probably gonna do some front V brake mounts. I've got some straight bosses already, but i don't think they'll line up too well so i might order some more 7mm offset ones like i used on the trike fork. I also have the option to do a fork swap, so i COULD go with a different size wheel up front if it would be worth it. I've got a nice Marz Bomber coil-oil fork tuned for my weight that i could use with 26" if i used a track hub. I bet if i filled it with really heavy oil and played with the valving it'd feel stiff but absorb hits.

The BMX itself is also not modified at all yet, i just made the bolt on front triangle and swapped a bunch of parts around. I could swap the parts back, put my pegs on and go grind ledges and huck stairs if my body wasn't all used up and worn out.

So i'm thinking, if the geometry works, this might be a good ride to use one of those 3000w hub motors i've' seen around, what's it called the MUX or summat? It wuold also be pretty simple to run a mid motor on this one, just stick it in front of the bb and go direct right to the freewheel. I could use a bigger freewheel in the rear, something like a 44-50t rear go kart sprocket for torque on a 58mm BCD freewheel flange.

While i was building today, i was tossing around the idea of doing a full-on electric conversion to my KLR 650. I haven't ridden it in about 5 years, partly because i've been needing to tear it down and do clutch mods,a big stator, port, polish, hot piston, and a bunch of other work on the internals, and partly because i just can't bring myself to use petrol as fuel, it's just too wasteful. I was considering running it on ethanol eventually, but i think i'm going to just do a swap, ditch the 650cc and find either a golf cart motor or a forklift motor geared low for torque. The original motor in the bike is around 40lb/ft torque and 48hp stock, but i did intake, exhaust and carb tuning as well as being 50lbs lighter in the front after ditching the stock headlamp, fairing, and all the useless brackets and such to support it. My new fairing from an inverted fender with halogen lights weighs like 5 lbs. What i'd want is a high torque setup, maybe a top speed of around 50-60 max with huge bottom end. The stock motor has torque, but this bike is just so massive that it takes a LOT of torque to really lift the front end, and after 2nd gear it takes a clutch bump to bring it up. Top end is around 110mph now at redline, my GPS said 109.8 but on a bike with a nearly 50" seat height and bars that are at eye level to me when on flat ground (i lifted it and did taller bars to fit me, i get like 16" of suspension travel) breaking 100mph is just downright scary, and i pretty much never really need to hit highway speeds. So, i'm going to try and find a motor that'll give me something with a LOT more torque than it has now, i want to be able to grab a handful of throttle and flip it over if i'm not careful and really be able to break the rear loose with power for supermoto style drifting. Basically i want too much torque so i can use what i want and always have some to spare.

But anyways, i need to figure out a damned seat for this thing, and i don't think the skateboard trick is going to work as well on this one. Man, i HATE dealing with the issue of a seat! I'd build more bikes if it wasn't for the hassle of making seats.

 

[amberwolf]

You might look at my Delta Tripper thread for some ideas.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=22720&start=25#p689786

It was a trike but used a BMX in similar configuration as it's base, though I attached the pedal boom to the frame not the fork. So the chain had to twist with turns--but I could still pedal while turning, and it did work well enough.

I did it that way because the pedals were really just backup in case of motor system failure, so it didn't really matter if it was harder to deal with pedalling in turns.


I used a rear wheel with singlespeed freewheel in the front fork,

https://endless-sphere.com/forums/viewtopic.php?f=2&t=22720&start=75#p716311


and I added rim brakes by taking the bosses and bridge off a junk suspension fork and welding them to the BMX fork.


desk chair welded to frame for seat

geometry discussion
https://endless-sphere.com/forums/viewtopic.php?f=2&t=22720&p=689786&#p692575

 

[Anonymous]

Wow, your trike is HILARIOUS! Hehe! I love the bars and stem!

On Monday i might be able to get to the hardware store and pick up a few things, one of them will be plywood to make a seat from, as well as a couple sheets to start my pedal-electric hovercar build. I think my next project is going to get the hovercar flying on pedal power, and then start working on putting together some sort of electric propulsion system. I'd really like to use a pair of EDF jets but i think i'm going to have to go with one or two big brushless outrunners with 18-24" props.

Ideally i'd like to use pedal power alone for all the lift, with a freewheel adapter and a flywheel on the blower shaft i should be able to get a decent sized skirt inflated enough to make it work.

But as far as wheels go, i may either try building a LWB recumbent or what i really want to try, a Warrior-ish style tadpole. Should i try 1.5" tubing for a cruciform tadpole frame or go right to 2". What size tubing does the Atomic Zombie plans call for? I'll go the next size bigger and make it beefy enough to handle me.

 

[Warren]

Here is one from 2007.

https://endless-sphere.com/forums/viewtopic.php?f=4&t=435

It resurfaced here.

https://gocarlite.com/electric-crank-forward-cruz-bike/

I fooled with a MBB back in the late 1990's.



The hardest part of this project will be learning to ride a MBB.

 

[Warren]

Twist-the-chain FWD bikes ride just like RWD bikes. There have been many electric assist ones built over the years.

http://tilting.org.za/bok/pedelec.html

The ZOX bikes are my favorite FWD, and many have been set up with electric assist.

http://www.zoxbikes.com/

Not their FWD, but fun electric assist in the snow videos.

http://www.zoxbikes.com/zox-video/

 

[Jost]

Interesting project. I've got a cruzbike Q that I'll be putting a hub in the rear in the next couple of months. Shouldn't take you too long to get used to riding the mbb......

good luck

Jim

 

[dogman dan]

Looks like you weld. You might look into making a more "normal" bent from some junk bikes. add a pylon for the pedals, and drive the rear wheel.

I just would not like the pedals angling on me all the time, as you do small corrections for balance with the front wheel.

This ones cool though, I did not mean it wasn't. Keep making bikes, its so fun and you learn from each one. Some of mine have gotten ridden around the block a few times, then retired after learning what that one taught me. All good.

 

[Anonymous]

Dan, I mentioned before in my other build thread (i think) that i'm on a mission to find a recumbent bike style that i like, and works for me, so my plan is basically to build one of each of many different styles of recumbent and see what clicks with me. I only built this thing because apparently this is something people ride, and i had all the parts for an easy build so it was next in line.

I agree this thing is weird and freaky, last night i was working on it, figuring out seat placement and thinking "So people actually ride things like this? Sure seems like a silly way to ride a bike!". And if ii don't like it i'll either fix the geometry if i think it's worth it to fine tune it or just unbolt the font triangle and build a bolt-on boom and idler mount to do a fixed bb rwd swb style and see if that does me any better.

I'm thinking my next recumbent frame is going to be a lwb built from a couple of old mtb frames stretched into something like, i think they're called EZ's or something.

Eventually after riding a few designs i'll get a better idea of what i really want to build into my touring rig. I've ridden a few recumbents before, factory bikes that a few customers had back in the day and i never liked them. Not as much because of the posture and riding style, but because every production ride i've sat on just felt small, flimsy, and not very confidence inspiring, as well as having fitment issues with my size 17 feet. If i didn't jam my toes into the front wheel on turns then i'd end up smacking my heel on some other part or dragging on the ground. As well, pretty much all the equipment that's standard on most non-hardcore bikes is a deal breaker due to my size and the power i produce. That's why i've got the 3 piece CrMo cranks and 420 motorcycle chain as a driveline, i snap regular "z chain" grade stuff like it's made of plastic. MTB cranks with square taper bb and bolt on chainrings would last until my first climb, isis cranks with beefy arms might work.

So i think i'm going to just build a plywood seat for this thing bolted right to the toptube with the backrest made from a seatpost with a piece of sqaure tubing welded at an angle and plywood attached. So far, figuring out a seat for these things has been the biggest challenge when it comes to these.

 

[Anonymous]

Okay, so today i tossed a seat and bars on this thing and took it for a little test ride.



Man what a silly way to ride a bike! I'm not really impressed with MBB so far The seat could come forward a few inches as i find myself stretching a bit for the bars and pedals and the rear wheel gets squirrelly in gravel or sandy spots in a non'confidence inspiring way.

Steering (if you can call it that) is imprecise and not very responsive, it's more like an approximate suggestion of direction than real control. It also needs to be a bit sturdier, i did get a bit of flex under hard pedaling and a bit of chain skip as it misaligned, but that's only because i make unreasonable power, if i wasn't using 420 motorcycle chain i would have snapped a regular Z chain before it flexed.

I might slide the seat forward a bit and pedal around a bit since i went through the trouble to build it, but i don't think it's really worth mounting brakes on. If i do anything else with this bike it'll be as a SWB recumbent with a crank boom and idler to drive the rear wheel. The riding posture isn't bad but i can see pretty clearly after trying this thing that MBB is more trouble than it's worth.

I think i might go get a few pieces of new metal this week, some 1x2 or whatever big stuff they have in stock and try to build a tadpole trike with a straight frame and the ability to take some 4" fat tires. I'm thinking of something tall and burly enough to actually ride it, something that'll suck up potholes, curbs, and be able to take some jumps, drops, and bombing over stairs and rock gardens.

 

[Anonymous]

Here's a short vid of testing, just a few parking lot laps.

https://youtu.be/BwXC6izf7q0

 

[amberwolf]

Steering (if you can call it that) is imprecise and not very responsive, it's more like an approximate suggestion of direction than real control.

Once you get weight on the front wheel, it'll be better--that's probably the biggest problem with SWB Highracers with seats too far back or too far reclined.

 

[Jost]

I view mbb recumbent as a cruiser rather than sport bike (they can go fast) as the steering has big built in dampers - your legs.......

 

[Anonymous]

I don't think i'll be going any further with this thing, it's not worth putting any more effort into since i got enough of a feel for it to know that i really don't like it. I'll probably convert it to SWB rear wheel drive this week sometime and try that as well, but I'm really leaning towards doing a high ground clearance tadpole as my next build.