MrInitialMan

https://www.mrinitialman.com/StandAlo...e_design.xhtml


So, this page shows the general shape I'm going for, the general length and width (not height yet), and some of the front suspension.

I hope this would be useful as a sort of blueprint and/or plan.

wsteve464

I don't know what you plan on making it from but it looks heavy, if it were me I'd consider a couple of cheap electric motor hubs for two of the wheels to assist on the up hills.

MrInitialMan

Steel tubing with 1/8" wall if I have to, aluminum if I can afford it. Since it will be a four-wheeler, motors are a no-go (Alberta regulations)

guy153

I would go with 1/16" wall if it's just mild steel (and even less if it's cromoly, but cromoly is much more expensive).
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MrInitialMan

Would that be strong enough?

Andrew R Stewart 

I suspect a lot of us here wonder about the strength of the rider being enough...

I forget why you feel the need for suspension. A performance go cart frame can see one wheel lifted an inch+ off the ground and still have the other three wheels stay on the ground. How much weight will you be placing in this thing? Andy

wsteve464

I admire your DIYness but this is way over built, is will weigh too much to pedal. Check images online to see what is needed in the way of a frame. Have you thought about making a pan type frame/bottom from fiberglass kind of like the VW beetle but fiberglass. Google quadricycle

Forum member cs641 in this thread https://www.bikeforums.net/framebuil...-builders.html. says he builds 4 wheel bikes similar to these
https://rhoadescar.com/

Maybe he would advise you.

Good luck

MrInitialMan

I'll be okay... I think.

• Iffy level railroad crossings.
• Poorly maintained roads.
• Winter driving conditions.

Yes, I know, that sounds like a whole lot of butthurt--because it is, in the most literal sense! Also, some of my instrument cases aren't very good at cushioning their contents.

There's a video of a guy riding a velo in winter.


The timestamp shows how bumpy the roads can be.

At least 250 lbs of me, plus whatever I'm tossing in the back.


I've checked out some images, including the Rhoades cars--which don't give much protection from anything beyond a light drizzle or a very sunny day. Sadly, I have NO ability to work with fiberglass. I was planning on using plywood for the actual bodywork.


So, let's leave the overall size and shape as it is, and add in the fact that I'd like SOME sort of suspension. Where would I save weight?


UPDATE: Just did some calculations, and the weight of the floor frame alone (using 16-guage tubing) alone is about 84 lbs. *Sighs*

UPDATE #2 The weight is around 55 lbs if I use 6061 Aluminum at 1/8" wall. *Still sighs*

guy153

Yes easily. To give you the ball-park, CroMo tubes are about 560MPa ultimate tensile strength and mild steel is about 400MPa-- so more than half. 0.8mm wall (which is about 1/32") CrMo is commonly used on bikes. So if you made a regular bike frame out of 1/16" mild it would be about as strong as a CrMo bike (on paper a bit stronger but we can deduct a bit for the fact that the mild steel tubes are just rolled). Also your chassis is probably going to have more tubes in it, so will be even stronger.

1/8" wall (about 1.5" diameter) mild steel DOM is about what they use for roll cages in racing cars. That's strong enough to crash at over 100mph. But your project has no engine and will be going more like 10mph. You want to keep it as light as you can. 1/16" is already overbuilding.

guy153

A project like this is in many ways easier to build than a regular bike frame. Thicker tubing is easier to weld. If it's mild steel you can hack it, bash it, reweld it, have lousy fitup, and make it do what you want without worrying much about heat cycles and cold working and things. And it's cheap. You can also build a bit of adjustment into the steering and suspension components to get the final alignment.

I think it's a lot of fun to make a suspension system. It all adds weight and drag and yes it does really need an engine, ideally something loud and screamy out of a motorbike, but if you build something like that you may end up attracting attention from the police, your neighbours, local regulators etc. I think an e-bike as has been suggested is a very good idea.

MrInitialMan

There is no such thing as a four-wheeled e-bike in Canada; power-assisted bicycles are described under Canada's Motor Vehicle Safety Regulations (C.R.C., c. 1038) as (amongst other things) " is designed to travel on not more than three wheels in contact with the ground."

A four-wheeled vehicle with a motor of any kind is a passenger car and subject to all regulations thereof. This is what I got from the Alberta DOT, and that's a can of worms I do NOT want to open.

By the way, do you guys think that in the floor frame I could get away with 1x1" and 1x2" 18-gauge tubing? That drops the weight of the floor frame down to 44 lbs. Even 16-guage brings it down to 58.

Or maybe even 1/8th" wall aluminum tubing of the same size?

guy153

How thick are your 16-gauge and 18-gauge? I think American gauges may be different than UK ones (in the UK 16 gauge is about 1/16")

wsteve464

Based on this and the overall weight you have to pedal I'd seriously think about about a 3 wheeler so I could hook up a motor. Use a cheaper suspension fork in the front and a trailing arm suspension in the rear with an electric motor in the front wheel or adapt one of the mid drive motors to the rear wheels and you could probably hit 30+ mph on the flats. Or easier to make as far drive train (and guaranteed fun) reverse the 3 wheeler and put the two wheels in front use a mid drive motor for the single rear wheel.

MrInitialMan

It will be a four-wheeler.

... where's the "digging in heels" smiley?

wsteve464

LOL

Well if it gets done at least you will be in great shape .

Ok last idea have you thought about a 3/4 inch plywood floor, instead of a metal frame, with a couple of metal cross braces to hold the wheels, that's it. And I am going with bonkers.

I wish you the best of luck.

MrInitialMan

What I actually had an idea of was to replace some of the crossbraces with flatiron, and much of the side tubes and the diagonal tubes with angle iron. Most of my weight will be on the center, anyways.

And the plywood sheet would be even worse for weight.

Andrew R Stewart 

I will defend your right to try projects that might seem like poor choices

Have you thought about the wheels and tires much? Tensioned spoke wheels have a very high strength to weight ratio IF the forces are kept in plane with the wheel's structure. The cars of yester year got away with thie design by having a very wide rim and more then two "sets" of spoke bracing between the hub and rim. Bicycle wheels lack these elements. Your 4 wheel design will not readily allow for the wheels to lean into the turn like a bike's do. Likewise the tires ability to not deform under turning forces will be challenged.

Designing the front suspension and steering geometry well will mitigate this to some degree (pun intended) and canting the rear wheels like some wheel chairs do will help that end of your machine.

As to the frame members I know thin wall Cro Moly tubing well so would likely use that. I braze, not weld, so would use that joining method. I likely would use various diameters and wall thicknesses depending on my thoughts about the stress levels each might see. I would hope that .035" and .049" walls would be enough for most parts. But I'm no engineer so... Andy

MrInitialMan

I was thinking of using mountain bike wheels and tyres for the front tires--I already have hubs for the back--as from the videos I've seen they're built to take a beating anyways. . Also, I was going to tell the bike shop that builds my wheels to use, and I quote, "the strongest rims and spokes that will fit."

As for geometry, I know the steering setup is over-complicated. That's so that the steering can be adjusted.


How much more expensive is Chromoly compared to steel or aluminum?

guy153

Tubing is usually better for a lightweight structure than flat bar or angle iron because it's so much better in torsion. The thinnest flat bar or angle you (normally) get here in the UK is 3mm ("hot-rolled"). A piece of 3mm angle iron is going to weigh about the same as 1/16" wall square tube of the same length, but the tube will be stiffer in bending and much better in torsion. The best bang for your buck is usually to use quite thin-wall but large diameter tubes (1.25" and above). The large diameter gives you a lot more stiffness. Steel is much stronger than you think so you're normally designing for stiffness not strength. Square or rectangular tube is very easy to cut and weld because it doesn't need to be mitred and you're welding in straight lines, but round is a more optimal shape.

Cromoly is about 3x the price of mild steel here but it might be different where you are. Bear in mind though that very thin-wall tubeis much harder to weld. Also, although it's stronger than mild steel it isn't any stiffer, so you will want large diameters and might need a bit more triangulation spaceframe type stuff going on.

Aluminium might be an idea but you need to be sure your design will be OK for fatigue and things-- steel is much more forgiving.

MrInitialMan

Aside from comfort, the other reason I wanted to have a suspension system is to cut down on torsion to the frame. I've seen some velo vehicles where the frame actually broke and had to be rewelded.



That's what I was afraid of...

Again, suspension system. Would that be enough?

Sorry I didn't answer this earlier. I think it's about the same (16 gauge being 0.065").

guy153

Yes suspension is good. But it will increase the budget quite a bit because the springs and shocks and things are all a bit pricey. I would go with 1/16" wall mild steel tubing which will be strong enough with or without suspension and cheap enough to make a few mistakes with and make the design up as you go along. If it all works well can consider rebuilding with more exotic chromoly later.

MrInitialMan

Well, I know the suspension will be a bit pricy, but a wise person once said "If you do not engineer a point of flexibility into something, it will engineer one for you."

I was also thinking using 1X2" rectangular tubing for much of the floor frame, with the tubing "on edge" so to speak.

Also, a bit off the topic of weight (sort of), would you all agree that I should have brakes on all four wheels?

guy153

Two rails of 1x2 on edge (1/16 in wall) and then a few lighter cross-pieces (which you can attach seats and things to) should work well. This is how people make hot-rods (they use thicker wall but they also have enormous engines). I think you do want brakes on all four wheels for stability and also heat dissipation especially since you mentioned carrying passengers and a bit of weight. If they're bicycle brakes (even disks) they will still likely overheat if you aren't careful. You could look at what brakes tandems have on them-- two sets of those are your best bet.

The only alternative to bicycle brakes I can think off is to use one car or motorbike disk brake on the rear axle like a go-kart. This would give you all the heat dissipation you could ever need on long descents. Bicycle front brakes could assist with emergency stops and day to day braking.

mikeread

I am going to enjoy this build, please keep us updated?

Since it is just for one person + load could you make the chassis much narrower to save weight and resist torsion.

This would give you more room for suspension which could then be something as simple as transverse leaf springs.

I am no expert by the way :-)

MrInitialMan

Okay, taking some of the advice--particularly that I'm underestimating the strength of steel, do you think I could get away with a floor frame like this:

CarCycle Design #3

I haven't put in the measurements for the floor frame, but I have for the overall body. For the floor frame, I managed to save around 24 lbs, so it's about 60 lbs instead of 84.

I don't think I could narrow the chassis much--I need elbow room. As for transverse leaf springs--I looked those up online, and they look like an interesting option. It was mentioned that they aren't great for cornering at high speed--but this isn't going to be a high speed vehicle anyways. I might use transverse springs on both ends--I can get away with that due to low speeds, can't I?