The following post will have numerous photographs, both of the model I built as a guide for the real thing, as well as photos of the actual frame.

The overall shape I had of my velomobile can be seen in this partially-complete model:



The general size can be seen in this photo of my Dad holding up part of the frame:



It's basically going to be a pedal-powered van.

What I'm having issues with right now is the rear suspension:





The issue here is the frame holding the rear suspension. As you can see in this photograph, the ends of it are simply out there in the open:




To me, that looks terribly flimsy, so I thought I'd make it part of a rectangular frame that would also support the ends of the shaft with the drive sprockets (the reason I have sprockets on that shaft instead of having the wheels directly on it is so that I could give the rear wheels some suspension. The freewheeling mechanism is on the differential, the rear wheels are fixed-gear)

So, the rectangular frame looks like this:





But I'm worried it takes up too much space beneath the velo and might not give me enough room to put in the hub gear and (if I need it and I probably will), an idler that will put the chain on the correct side to link up to my differential hub properly (that's where my coaster sprocket is). Or is ~30" still plenty of room for mechanics and I am worrying over nothing? Just a point of reference--the rectangle with no uprights inside it yet is towards the rear of the velo, the one with the uprights with holes drilled in them is towards the front.

I'm having trouble visualizing what you are trying to do. I think you are going to need to have parts available to mock it up since you didn't have the actual parts in your prototype

I was hoping to have some bracing for the frame that holds the rear suspension. I think I know how I can do it, though. Just had to let it percolate in my head.

Well, I followed some advice given elsewhere and made a sketch on some graphing paper:


Each square represents five inches.

The blue is the main frame, made of 1X1" steel tubing (1/8" wall). Inner (long) frame is 110" long and 10" across, outer (short) frame is 80 inches and 30" across.

The red is the underframe, also made of 1X1" tubing. It will be about 50" long and 7" across (outside, 5" between the two tubes). The mechanics will be attached to this, and it stretches from the frame that supports the front suspension to the one that supports the rear suspension.

Green is the suspension. The rear suspension will be a rectangular U shape (since it was already built), and at the advice of the board, I think I will have it as sort of a swing-arm setup (I'll just need an idler or two to keep the chain from rubbing against the frame) or I will use what I had in the model.

The front will be a double-wishbone suspension on either side. The pencil-grey circles are the wheels (I'm going with 28" wheels), and the purple line with the squiggle over it is the spring for the rear suspension.


I'm thinking the final weight of my velo will be 200-300 lbs (100 - 150 kilograms).

Why do you need suspension? adds a lot of weight and complexity. Why not use relatively big tires? Overall every bit of weight you add decreases your payload potential. and there is no way this thing can be used on anything but a smooth road based on size and weight

If you end up with a 300 pound velo and a 300 pound payload, and a 180 pound driver you are at 780 pounds gross weight. That is a lot of weight to pedal and bring up to any sort of speed. More importantly that is lot of weight to stop, especially if you are on any sort of downhill. Will your planned braking system handle stopping 780 pounds going 15 mph on a downhill?

OP, I know you are fixed on doing a velo mobile.....still not sure why that design really, but here is alternate design inspiration to consider if your focus is on hauling cargo.

Main Street Pedicabs? | The Pedal Pickup? an innovative way to provide cargo transport.

Because I live in Alberta, and a thorough description of the weather here would result in the moderators demanding I wash out my keyboard with soap.


Because I don't think that even fatboy tyres can compensate for what snow makes these roads like, and turning out of a parking lot which meets the street at a steep angle does ...interesting... things to a quad frame. And besides, aren't really big tyres usually pretty soft, and thus harder to pedal anyways?

First off, no need to flatter me--I'm well aware of what a fatso I am. (I'm a good 70 lbs over that). And I'm planning on having brakes on all four wheels. As for a 300 lbs payload, well, not sure if that's going to happen. The main focus is hauling ME around and whatever baggage (physical, that is) I'm bringing with me.

But since my recent rant under "Frustrations Mount", I have calmed down and am ready to return to the project. On to dubious success or absolute disaster--and if it must be the latter, here's to making it a memorable one.

Maybe I should take it to a paintball field and let the people there "paint" it.

Main frame mostly done.

so that is right side up? That's going to be quite a vehicle.

That is indeed right side up. The small "box" at the front (right) will support a double wishbone suspension. Where the vehicle flares out in the rear is going to have an 8-point suspension (as seen in my model pics).

It looks like an interesting project.

If you made the frame with chromoly, you could probably use 1/16" tubing, and cut the weight of the main frame in half. Also consider 3 dimensional "truss" designs.

200 to 300 lbs will be heavy!!!

I regularly tow a trailer, and can certainly feel it drag once I reach 200+ lbs. Hit 500 lbs, and the hills are killers. But, even riding on flat land is hard with heavy loads. Even road crowns can be a pain.

And, yes, the weight of my trailer did add up quickly when I was building it... It doesn't take much for just the bike or trailer to get heavy.

Have you considered provisions for motor assist?

I'm just working with the materials I have (which is steel). I don't know if my Dad has the materials to weld chromoly, and I know he doesn't have any of that material.

Yes, I looked into it. It turned out not to be a good idea. HOWEVER, if this thing does prove to be so heavy as to be unusuable, I will build something a bit lighter and either sell this one to someone who wants a good leg workout or put a motor in it and have some fun at the go-cart track. Or just use it to drive around our acreage.

It never hurts to prototype and experiment with cheaper materials, then take what you learned for building V-2.

Do you have TIG capabilities? There are quite a few low cost TIG power supplies that you might consider.

We do not. Dad never learned to weld aluminium, and I never learned to weld at all.

Oh, good, it never hurts to learn something new

In a sense, TIG is similar to oxy-acetylene welding, but with electricity, and is handy for thin materials and sheet metals (and Aluminum, although one can also MIG weld and even braze Al). At the same time, no sense in investing a lot in equipment that will never get used.

Yeah, that's the issue: My dad's shop is almost devoid of business these days (to the point he's considering selling out), and he's well into his 70s.

It's one reason he's so willing to help me with this project: it's something to DO.

EDITED TO ADD: I just weighed the frame. As is, it's about 100 lbs, but the main part is virtually done.

I understand alberta weather....grew up in montana and watched a lot of tv from lethbridge (and to date myself, that included "The Friendly Giant" and ads for Old Dutch potato chips. My hometown was -29 F two nights ago

they do make some huge tires....even snow tires, just for reference.



In the big picture, there is lot to be said for doing a project with your dad.

Just trying to make sure you consider options.....good luck with this will be watching

I think that by now I've gone too far on my current frame to really go back; I'll mostly stick to my original plan and see how that works out.

Think I can get sheets of fiberglass from an auto body shop?

Sheets? As in already manufactured stiff panels? Or are you looking for bare fiberglass to epoxy? Look to boat builders or marine supply stores.

These guys are in Edmonton - https://boatcraft.com/

Already manufactured stiff panels, preferably. I'll have to look up someone in Calgary. Edmonton's a bit of a drive--well over 2 hours.

Boatcraft does mail order. It is much easier to work with raw carbon/fiberglass weave than have to deal with rigid panels. Cutting composite panels can get messy and leave you with subpar results. Raw cloth can easily be cut with heavy duty scissors (just use wide masking tape on the cloth, front and back, and cut it down the middle. It also creates MUCH LESS dust which is a respiratory hazard as well.

If you're looking to give shape to your project, and not use the panels as structurally stressed members, then maybe look at Dacron cloth. You lay it over your frame, affix it at the edges, then take a blow dryer to it to shrink it over the frame. You can try a heat gun, but practice first. Dacron shrinks at around 225-250F, and melts at about 425F. Maybe a used Clothes iron from Value Village would be a good idea as the heat is easily adjusted and low enough. Don't use your significant other's or mother's iron.

Once it cools, you paint it with some epoxy and it seals it up. This is how skin on frame kayaks are made. It will end up much lighter than using fiberglass and look much better as well.

Below is an SVG diagram a part I intend to use in my rear suspension:
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Why use 3/4 X 3/16ths flatiron? Because it's what I've got lying around. (In the same vein, why use SVG to make a diagram? Because I don't have photoshop and I can barely use GIMP, but I'm good with XML. In other words, both are what I've got to work with).

Here are the plans for the bars (there will be a total of 8 of them).

Rear Suspension Frame of my velo:



The one upright piece is being held in with clamps because it hasn't been welded in yet. Once it is, 1" sections of pipe will be welded horizontally to the top and bottom of the upright pieces that DON'T have holes in them.

Below is the basic rear wheel frame of my velo:



It, too, will have 1" sections of pipe welded horizontally to the upright parts. I've taken pictures of my model to show how the diagrammed parts will work.






So there are four of them for each wheel frame.

Do you think what I have will be sturdy enough to hold 200-300 lbs of velo and 250 lbs of fatso (me?) Or should I figure out something stronger?






*Sighs, looks at his post* I'm not making a lick of sense, am I?

A couple of comments- While the vertical capacity of your suspension system might be up to snuff I question the lateral strength. I see no bracing/struts to help with the side forces that turning will produce. I would experiment with side loading your mock up and see if there's much movement. The other aspect that I wonder about with suspension is how the drive forces will be sent to the wheels. Suspension means that the driven wheels are a moving target. So a chain drive will see tightening and loosening of the chain. Careful drive cog/wheel travel arc pivot (as in a simple single swing arm) address this but with a parallelogram controlled wheel movement wheel travel path changes differently. two wheeled bikes with driven wheel suspension generally have a chain tensioner (a rear der) in the system to take up/play out chain as needed. Andy

Trusses where? Unfortunately, the mockup--being built of Merkur--has the slop inherent to a construction set, so my results would be suspect.

The pictures are in the folder https://www.mrinitialman.com/Standalones/Velo/ if you want to have a look.

Already have something in mind to deal with that: VeloSolo - Forged Singlespeed Tensioner Failing that, I would have just gotten a couple of rear derailler shifters and locked them in place.



EDITED TO ADD

Or did you mean something like this?, where pairs of suspension "bars" are joined by a crossbeam at one end (I can't do both ends; due to the wheel)

just for fyi check out this at about 24 seconds, shows a student built velo cycle, but it looks like it has front electric wheels.
also, what are you planning to do with the fiberglass panels? if it is for sheathing the outside, Coroplast may work, or you might even think about using really heavy visqueen for prototype?