Guru advice for super large rider

Hi all,

I've been researching for months and I'd appreciate any review of my current leanings to make sure i'm on the right path for my specific weird situation / disability / whatever you want to call it.

I'm near 700 lbs. Yeah, I know. I carry it very well for 700 lbs, but it's pretty hard. I can walk into work but I have to stop and catch my wind on the way in, etc. I used to ride at 450 lbs and got in pretty decent shape as I got down to 400. But, that was a long time ago and even then I was on a recumbent that I had to push up a lot of hills and the front wheel was so small I zig zagged all over the place going uphill.

I know that I need a trike and electric assist. I can't find anything commercially that I'm willing to take a chance on. Being a handy guy, I've been researching and designing. Here's what I'm thinking, and I'd appreciate any feedback. I'm still reading but I think I've settled on some stuff and want your thoughts.

0) Pushing a 700 lb man means that I don't need a 40 lbs vs. 50 lb bike. It can be heavy.
1) Custom frame - made from big strong tubing.
2) Tadpole trike
3) Motorcycle front tires - 100/90-19 wheels (Almost exactly 26" OD)
4) Rear drive (simpler)
5) 7 speed rear dérailleur, single speed front sprocket (don't care about speed, just hill climbing)
6) Rear drive with the "GNG big block alternative" (logic below).
7) Dual front 160 mm disk brakes
8) Custom seat w/ pipe and nylon netting - adjustable angle
9) Adjustable pedal position (obviously would have to adjust chain).

A few points that went into above.

Tadpoles are cooler to me than deltas. Also, the way it's currently designed it's easy to arrange the drive stuff and and use standard parts from an old bike and overall easier. Makes the steering harder, but I'm willing to bite that off.

My logic for rear drive is that I have very powerful leg muscles from moving 700 lbs around. I'm assuming that since I have in the past folded chainrings by accident that I have more than sufficient power to do it again if I'm not careful. I like the idea of a mid-drive, but I figure if I throw 1000W into the BB in addition to my major muscle power, I figure I'd destroy most normal chain gear.

I also like what I read (so far - the thread is enormous) about the BB motor - about the high amps at low volts for torque and then higher voltage for speed (the Tesla analogy in the thread). I'm still working out controller / volts / amps, etc. But I figure that the direct drive will be a good idea in hill climbing.

On gearing I figure I'm thinking a 14-34 7 speed on the rear and 32 tooth front (the normal mid ring). This gives 24 gear inches / 5.8 MPH with a cadence of 80. High gear gives 14 mph at 80 rpm cadence. Either that or 22 tooth front gear which gives 17 gear inch / 4mph low and 9.7 mph high.


So right now i'm after does this make sense so far? Which threads should I read up more on? (I have about 4 open right now I'm in the middle of and have been researching for months). My plan is to get out in the garage when the temps start dropping (fall). Build through the winter. Test ride as soon as things warm slightly. Start real riding ASAP in the spring.

I appreciate any pointers / thoughts / etc. that you have. Thank you for reading this and sharing your opinion.

Holy smokes !!!... 700 Lbs ! .. please understand i mean no disrespect , but how tall are you ?

I'd contact http://worksmancycles.com/shopsite_sc/store/html/specialneeds.html and tell them what you need. Let them build the frame/tricycle for you. Then get a good electric conversion kit and put it on yourself. Add battery - here's where you should direct your time & effort - its the expensive and indispensable thing. You'll want to get a big enough battery for BigRider to go the distance you'll need.

Most of the tadpoles I've seen are fairly low to the ground for reasons of stability, is getting in and out of a lowish seat an issue for you? I'm only a little over two hundred but old enough that getting in and out of a tadpole regularly is not something I'd look forward to.

Thanks to those so far.

6' 1". And yes, holy smokes :/. Been a life-long struggle. Part medical, part behavioral. Combined = toast.

I did look at worksman cycles. They couldn't guarantee or even give me warm fuzzies about the tires holding up. Even with kevlar and all the bells and whistles. I had talked to Ding Bikes, but it was going to be 3500$ sight unseen - can't even sit on one. Their base was a worksman trike. I researched buying a worksman directly and decided that with about 50% of the reviews saying their quality was horrible and customer service non existent and 50% sounding awesome, it looked like their QA department didn't exist. It sounded like either you get it right the first time or you're screwed. I didn't feel like a 1500$ gamble on 50/50 odds, esp since I'd have to customize pretty heavily.

I'm not building a super low slung trike. I don't plan on going all that fast. So getting up and down should be OK. The seat will likely be about 2/3 of the way up the wheel, so around 15-18 inches above ground.

And yes, holy big battery batman!

I think of this one as the Mark 1 iron man suit. Once I've proven I'm able to ride, lose a bit of weight, and find it works I'll design a more elegant version for season 2 .

Do a collaboration with Workman - let them build the frame for you. These are industrial grade frames. Then put moped tires on it and so forth.

To build it yourself the question is what level of fabrication skill are you starting from and what tools do you have?

Also budget?

I'm fairly committed at this point to making my own. Not only do I think it's fun, I know I can fix anything that breaks and make it out of much stronger materials in the first place.

Budget? .... what budget . I'm looking at it like if I don't do this I might as well go ahead and give up and die. Not really ready for a grave just yet, so .... gotta do something. Biking is the least annoying exercise option available (get to go somewhere!), but I have to go carefully now. On the other aspect of that question I can afford whatever if I take it in small chunks.

I've spent 2K in tools so far and 500$ in parts so far (stuff I am pretty confident I'm using like pillow block bearings and the wheels). I expect I'll be dropping another 1500 minimum in the electrics and raw metal. I'm re-using some stuff from an old bike. Decent MIG welder, grinders, cutters, drill press, and other stuff.

Fabrication skill. Um. Well, I won't put my rear on it before I'm really sure it'll hold . I've always been mechanically inclined and I am pretty confident that before I get to real fab I'll be ready to do it. I'm simultaneously researching / designing / solidworks modeling and on weekends practicing welding, fab stuff, etc. I also have access to several super high quality fab guys I can lean on for education if I'm not making the progress I need on my own.


So my real question isn't "should I make my own", but "does it look like the general shape of the path and decisions so far look like it has a chance in hell"?

(also - I'm Central time USA and about to head to bed and only can get on this post after the kids go to sleep - I'll answer / respond to anything else in about 22 hrs .

I should also add I spent 1.5 months reading every single night (and talking to vendors) before deciding yes, I wanted to fabricate.

And I know good and well it's easily the biggest project of my life - even bigger than the 12x20 workshop I built with full electric, etc .

The amount of information I've learned so far is utterly staggering. The amount left to learn is even more staggering. But I'm in it and committed.

Sounds like a fun project.

I think you should consider a motorcycle rear wheel and hub, too. You can add the derailor to a jack shaft that feeds the motor by another chain.
However, I can blow up a chain and freewheel and I'm only 185lbs. with your leg strength and pulling your weight up a hill, you could collapse a bicycle hub. Infact you might even consider a motorcycle transmission instead of a derailer. Bike derailer can only handle about 200lbs of torque. If you can stand on one leg, you can produce at least 700lbs of torque with 32/32 gearing.

Since you're looking to move motorcycle levels of weight, you might look at John in CR's midmonster motors instead of the little GNG. people break GNG pushing them hard. The Midmonster is a whole new level of motor.

Hi Drunkskunk. I appreciate your thoughts. I also think it's fun, which is another reason I've been working so hard on this - way better than being bored looking at silly pictures and watching netflix every night).

Never heard of midmonster. I'll look into that.

In essence my plan is what I think I read you saying. My rear wheel is technically a front wheel, but I'm making an adapter to tie it to the rear shaft. On one side was the plan to use a freehub / 7 speed and on the other was going to be a bigger gear that attaches to the rear drive motor (with gearing I haven't figured out yet).

I'll have to look into that derailer / motorcycle thing. I can do a lot more than 700 lbs of torque .

Big guys need small wheels with big tires, that is where your ebike build is starting.
Then, considering your total riding weight, you will need a lot of power and motorcycle brakes.

For tires, the toughest around here are the Moped tires. A Pirelli ML75 will fit on a 20-inch rim.

"Moped Tires"
http://endless-sphere.com/forums/viewtopic.php?f=3&t=40123

Thanks MadRhino. Why do you say big guys need small tires?

SpinningMagnets - Hello fellow Kansan! I noticed you were semi-local and a super guru. I've read all sorts of things that you posted. And thanks for the moped tire link.


If there are any other good threads or advice I'd appreciate them.

You'll have to build your own or have it custom made. Take a look at http://www.atomiczombie.com/DIY Plans.aspx. I think several of their designs will work for you, and just build in more strength and use car or motorcycle tires. What kind of performance are you looking for? What is the terrain, hilly or flat?

I agree with Jonathon, forget the tadpole trike. It will be too difficult to get in and out of with the seat so low to the ground. Raising it up enough for you to reasonably get on and off eliminates most tadpoles because the steering and wheel support linkage will get in your way?

I think a feet forward semi-recumbent is your best bet. You definitely want a comfort seat. It sounds like you definitely want to pedal. I think your biggest focus should start with something easy for you to mount and dismount. Maybe I'm wrong but I don't think you want something you have to swing your leg over due to knee and ankle risk of pivoting on one leg.

Good luck with it.

arkmundi said:

Do a collaboration with Workman - let them build the frame for you. These are industrial grade frames. Then put moped tires on it and so forth.

Click to expand...

Worksman frames are heavy, and durable. Trust me that they are totally unsuitable for the problem at hand. They are designed to withstand harsh use and neglect, not huge forces.

I align the front end of my Worksman Adaptable trike by just taking the bars and pulling them to the side while sitting on the seat. I weigh less than half what the OP does.

As for what I'd recommend to the OP, well, a pedicab trike would not be a bad starting point. They are designed to take the weight, and they use simpler, more rugged components than a tadpole trike.

EDIT:

Note that normal bicycle cranks and pedals won't be safe at these loads. The chain and sprockets will likely wear out unusually quickly, but the pedals and cranks can simply break off and cause a crash or injury.

The saddle and seatpost will have to be special too. And possibly the handlebars.

Small wheels are stronger than big ones all else being equal, a 20" wheel is considerably stronger than a 26" one, particularly against forces from the side as you see in a non-tilting trike. On the other hand fat tires support weight and absorb shocks better than skinny ones so small(ish) wheels with fat tires is the way to go

Bear in mind that getting on and off a tadpole trike you won't have any handlebar to hold on to for balance as you step over the frame and lower yourself onto the seat. If you have to step over something 15" to 18" high that's a fairly significant balance problem for someone your size I suspect. I would mock up a bar at that height above the ground and see if you can swing your leg over it while not holding on to anything before you even start to design your trike.

Also with a lot of weight on the tires all your steering linkages are going to have to be very solid in order to work without flexing as you're trying to turn, things like bump steer will be greatly exaggerated over a similar system with less weight on it. Designing and fabricating the steering knuckles and getting all the geometry right including the Ackerman is going to be a major effort, that's a whole set of headaches that you avoid with a delta trike.

I think something like this stretched delta style trike would be easier and simpler for a first time builder to fabricate and would give you a handlebar for balance as you mount and dismount. With the stretch on this the weight on the steering wheel out front will be fairly low and the steering linkage won't' be nearly as stressed as it will be on a tadpole with most of your weight above the steering tires. To avoid needing a differential you drive one wheel with the pedals through gears and the other wheel with the motor. Come to think of it if you use a direct drive hub motor with a chain or belt reduction to the axle you could even have regenerative braking if there were no freewheel involved, the greater the mass the more benefit you get from regen.





A similar style not stretched out quite so much, notice how the stepover is considerably lower than the seat and the handlebar is right there for support as you swing your leg over.



Oh, and after looking at Chalo's comment again here's a pedicab frame, you would be riding back where the batteries are and the handlebars would be more or less where the saddle is on this.

Small wheels for the win for sure. I'd tend to still be looking at tadpole, but not so low. I'm assuming you build it.

Then use a pretty powerful scooter hub motor and tire on the back. Not sure how to adapt that to pedal assist, but one opion could be to pedal a generator. So what if its horribly inefficient, the idea is to just get your legs moving just enough to keep the clots from building up in your legs. You could literally even be pedaling a regular exercycle, not contributing anything to propulsion.

Another option, a delta trike based on a golf cart rear end.

John in CR: Thanks for your thoughts. The tadpole I’m working on in Solidworks should have the seat high enough to get in and out of and I’m pretty confident the step-over wouldn’t be hard for me. Strangely as it sounds, my body frame is built for carrying massive weight. At 400 lbs I was in fantastic shape able to easily ride 20 miles at a pop. Boy … to be “only” 400 lbs again :/. But anyway, I think that there’s a lot of validity to the concern of mocking up my seat height and stepover just to make sure because yes there is a certain height at which it gets to be a real PITA to get off the ground.

And it was Brad’s plans at AZ that convinced me that I could not only design the frame but fab it myself (after lots of welding practice). His plan bundle of 6 was the first pennies I spent on this endeavor.

My reading over the last few nights has made me question delta vs. tadpole, but not for the reasons you mention. If I go with your mini-monster – which looks awesome – I’d probably put the tire on it and then make that up front. Then do pedal assist to one side of the rear axle. The problem is tadpoles are just cool … but maybe I save that for rev 2.

Chalo: Thanks for the pedicab stuff. I also agree about pedals and cranks. I had already planned to make my own from scratch mainly due to the fact I want them 12” or more apart between the pedals just due to geometry of my big-ole-legs. At 400lbs on normal crank I had knee unhappiness and wanted the pedals farther apart. I’ll look into pedal cab frames a bit.

I’m planning on custom making the seat out of 1” OD heavy wall pipe and using a friend’s hydraulic bender and his 30+ years experience of welding to make that. I’m planning on a bar to the left and right, shaped to a “L” and then tilted back. Then using a nylon mesh webbing between.


Jonathon in Hiram: thanks for your multiple inputs on this. One thing I keep in mind is that I’m not going to go fast. My upper end speed is 15 mph. Max. I’m gearing it down for weight carrying capability.

I was planning to have a friend who’s a lifetime pro welder help with the steering knuckles just because I’d be concerned about them failing and my little MIG not having the juice to make those right.

Regen is definitely interesting. I have a lot more reading to do on that .

The red frame is interesting. Maybe that with a mini-monster up front and my motorcycle wheels in the back (already purchased, and are super crazy heavy duty for this use). But even if I started with that red frame I’d have to basically take it down to bare metal to do all the mods I know I’d need.


Dogman: Thanks. I do think I’d need the pedals to move the bike. I have a strange brain when it comes to exercise. The exercise needs to accomplish something. I HATE the gym, but back when I was more physically capable I’d easily get out a chainsaw and about kill myself with cutting down trees on the old farm. I’d work 100x harder on anything that actually does something. I’d never be able to handle (mentally) the riding on a stationary bike – or regen – but getting out and pedaling around town would make it far better.


All – I appreciate your inputs and any more you have. Right now I’m leaning towards either a tadpole with a rear drive big block, or a delta with a mini-monster. I have a lot more reading to do before settling that question .

And, if anyone has any pointers to threads about or references to any higher strength gearing options I'd appreciate them. Anything that's not hundreds of extra pounds to the bike but can handle the strength of my pedalling w/o disintegration (e.g. a 219 chain version of a derailleur setup, or a super heavy set of regular gear, etc).

The Sun USX is rated for 400 lbs. A bit of strengthening of the frame might be all the you need. I would ask Sun in Miami. It has 48 spoke wheels too which are really strong.
otherDoc

I love ES lots of good folks here to help. My advice is to stay with a hub motor or a really strong chain drive motor, because as Chalo said the bicycle chain forces won't hold up for long. I think a really nice pedal assist torque setup would be good so that you are always adding at least some input to keep the rig rolling down the road. Ebikes can save lives! The joy of the outdoors and the exhilarating feeling is the reason we are all addicted to them...LOL. Good luck and please post your build pics eventually.
8)

Some thoughts:

• Regen would appear to be a waste of time at the speeds you are considering and may complicate drive considerations if you go delta. Simple is best here. Carrying a couple of percent of extra battery involves no complication and will accomplish the same goal. If you go tadpole and it's free - fine - but it should not be a design criteria.
• For a delta config, I believe you should be looking at driving both wheels. This is an expensive and long build and it seems pointless to make such a large functional compromise for the sake of a design simplification for a problem that does not appear that challenging.
• I appreciate your enthusiasm for the tadpole and the simplicity of the single wheel drive, but a delta is a much simpler fabrication. You are learning a lot in many new areas and avoiding design and fabrication issues of an effective tadpole front end might be worthwhile. This simply removes the issues from the build as you focus on other problems and new knowledge areas - a matter of risk/time management. Maybe save it for Mark 2 and the new 400lb you - when some steering load issues will be be lessened.
• A quick look at the pedicab rolling chassis in an earlier post leads to the manufacturer. This thing has a modified go-kart diff and other goodies. On casual inspection, the firm seems to offer parts and custom machining. At the very least, this might get you a whole lot of drivetrain even if you fab the frame yourself. I really have no familiarity with other available solutions in this area, but this seems a rugged and proven solution to your exact issue that would jumpstart your build and give you easy future maintenance and support.
  • MaxiPro EcoTaxi
  • Custom Kart Parts for Pedicab Drive
  
  
• A consideration for direct hubmotor drive might be low speeds (15mph max) and high torque you are targeting. This is certainly doable but is the operating range where hubbies fair the worst and gobble amps. I would personally be looking at some gearing to get the motor into a decent operating range to get the most range from my batteries.
• In the more speculative area: This is going to be a big moose bike that I am certain will be life-changing and that you will enjoy. I'm thinking that it will not be long before you may wish to cruise new destinations. It seems that if you build a delta with Kart and mortorcycle quality rear components, you might be able tow it at moderate speeds. The unoccupied bike will be relatively light and should ride fine on the fat tires without springs. A removable front hitch for the bike or a custom bike front wheel carrier for a standard auto hitch receiver would allow you to just lift the front onto the hitch or wheel carrier and plug in the tail lights. Off you go to a new adventure...
  (just a thought )

Again thanks to all for your inputs. It’s certainly steering me down a different path than I had anticipated and I’m very glad for your thoughts and input.

docnjoj – Oh boy. I think modifying a round tube suspension framed bike … yeah, maybe that’s mark 3 .

wineboyrider- thanks! I am now wary of standard gears . And I too hope it’s a lot of fun and I finally find something addictive that causes me to like weight loss .

teklektik – regen: that matches my original thoughts on the matter, but with this much mass …. . Makes sense though.

You may be right on saving the tadpole for version 2. Maybe I’ll see if Ecotaxi will sell me the frame, gearing, axles and whatnot, leaving off the wheels and their electrics. It looks like something I might be willing to start from . I could also seeing this being a good candidate for a rear drive or mid-drive (with some mods).

And I never thought of the idea of towing it. That would be a good idea.

A few thoughts from someone that hauls a lot of heavy cargo around on not-so-great streets using DIY bikes/trikes. Not up to the weight you need to move around, but I have thought about something that might do that now and then, as a "moving van" sort of thing for occasional use.

First: Listen to Chalo; he knows what he's talking about here.

Some thoughts of my own:

With the weight you need to support, you might wanna go with mostly motorcycle or at least moped parts, rather than bicycle ones, especially if you want any suspension (which I'd highly recommend; it's way easier on the wheels at that weight, especially if you don't have perfectly smooth roads to ride on).

Not only are the wheels stronger, but they have brakes that can easily stop you from any bicycle-class speeds, even at the total weight it will be at. from 15MPH they'd probably last forever. Bicycle brakes might work, too, since you don't need to stop from high speeds (but the load they will see is probably as if I was stopping from 20MPH on my CrazyBike2), but the MC stuff will definitely work. At those speeds regen braking as noted by Teklektik is probably not worth the complications, and if you don't need it it opens up drive possibilities you don't have if you require it.


At the least, if you are doing a tadpole, you may want to use a MC swingarm and rear wheel, along with it's suspension. Might not be needed since you're not going fast, but it'll definitely take the load you've got, without making your own.

Then use the MC chain and sprockets to run a middrive, so if you like you can use a powerful motor where you can set it up for whatever gearing / etc you need (and change the gearing easily enough later on if your needs change, or even use a shiftable transmisison if you have to), and not have to worry about building it into a wheel. The chain and sprockets won't wear like the bicycle stuff would under your loads. You sitll have the problem of typical bike cranks/pedals not being really strong enough, but that's osmehting you may be able to make your own solution for (Chalo might have

You can use a jackshaft to combine the motor and pedal power to get it to the drive wheel.


You could also put motors in or chained to each front wheel, which will increase your traction under power, but also greatly increases the complexity of the front end (and electrical system, control, etc).




Tadpole vs Delta: I've argued with myself about this for years. :lol: There's a number of advantages to tadpole, particularly in cornering at speed, but if you don't need to do that, a delta has other advantages that may well outweigh everything a tadpole has to offer:

Construction is much simpler, as is steering.

At least 2WD is also much simpler to do with delta, and because a fork holding both ends of the front wheel axles is usually used, you can actually easily do 3WD, either with a hubmotor or a chaindrive (motor mounted on fork). As noted above, you can use differential at the rear axle to apply power evenly thru turns, too, both from pedals and motor (assuming both run thru the same chain).

Cargo area between the rear wheels is easier to setup than one in front, without using small wheels in front.

I had some ohter things in mind but got distracted while typing and forgot.


You can also pretty easily still do a partial-leaning design of delta, so that you can lean into turns with your weight, and turn at speed wihtout much issue. With the weight you have to deal with you'd have to build the pivot differently than I would (much stronger) but you could do it. It does complicate things, though, including the pedal drivetrain, but one solution for that is to use a driveshaft thru the pivot point itself and chains on either end...but this again really complicates things.



About the only other thing to say is to be sure to put as much of your weight as low as you can, as it'll help you in turns.