[Woodsmith]

One of the issues with having your kids with you is that they are going to be a significant proportion of the gross weight. Your weight balance is going to be hugely affected by having or not having your kids there, or by only having one kid or if one of your kids if heavier then the other.

I once tried riding a tadpole trike that had a wheel chair on the front ahead of the front wheels while the 'driver' sat at the back over the rear wheel. It balanced fine while both were on board but was almost unridable without the wheel chair passenger. Also, when the driver got off to attend to the passenger the whole thing tipped forward!

I would prefer the trailer ooption if it were me and then incorporate mirrors to see behind and keep an eye on them and maybe the sort of intercom ystem used by motorbikers and their pillion. You could also add a dvd player to the back of your seat!


Laminations can be made up with lots of cheap G cramps, but you do need lots to get an even pressure.

If you can get hold of a vacuum pump you can make a vacuum bag which will be a lot neater. It may be beyond your needs though.

We can discuss the making processes as you decide what you are hoping to make.

[toddshotrods]

Originally Posted by Woodsmith

...I would prefer the trailer ooption...

Check on the legality of that where you live. It could be illegal to have your kids in a trailer behind you.

Originally Posted by Woodsmith

...with lots of cheap G cramps...

WHat are those and where do you get them?

[KrisWood]

While waiting for an opportunity to get my tools and some building materials I'm fiddling with the concept design some more. Today I've been combining elements of the Thunderbolt MkIII (Spitfire RS26) with those of the Zelo.

I'm keeping the proportions of the Thunderbolt while integrating as many woodworking elements of the Zelo as possible. Unfortunately I suspect it's quickly exceeding my ability to manufacture.

I think what I'll do for now is imitate the older Thunderbolt design off the ihpva web site since it's much much simpler and save the curvy version for Prototype 2.

[Woodsmith]

Be careful getting the proportions right for you. Make a mock up around a seat and BB with pedals to work out how long you need it to be and where the wheels will be and the space for turning the front ones without clashing with your hands when steering.
The mock up need not look like a trike at all.

This is how I started working on mine. The seat is laminated from two sheets of hardboard.

Originally Posted by toddshotrods

What are those and where do you get them?

Trawling through car boot sales often turns up good ones for little money, otherwise cheap sets of not so good ones from Machinemart and DIY sheds.

However, homemade ones are also good and cheap, so long as they are not CAD drawn and CNCed from billet.

[KrisWood]

Thanks for the tip, I'll definitely keep that in mind. The nice thing about the Thunderbolt design is that the pedals are adjustable, and the steering is via a single tiller so no worries about squishing hands. I made a mockup already to get an idea for dimensions but haven't tried sitting in it yet, I guess I should do that

Another thing to keep in mind with the Thunderbolt design is that the seat is not part of the trike's frame, but rather made up of its own separate framework which is then bolted to the frame trike's This means that the seat will be constructed in a way that fits the driver and not entirely restricted to the frame proportions.

Still as they say, better to measure twice and cut once.

Edit: Here's the completed main frame of the older Thunderbolt design if it were made of wood. I think the "keel" (for lack of a better word) may need some thickening, we'll see

[KrisWood]

Oh! I figured out the drivetrain problem!

I've been trying to figure out how to adapt my motor to drive the rear wheel. It occurred to me just now that it's not the axle that turns, but the wheel itself, so I'm really stuck with one of two options;

1: Have a combined drive train with an intermediate axle that combines the torque from both the pedals and the motor and then applies it to the rear wheel via another chain.

2: Build the pulley from the treadmill into the rear wheel's hub and have the motor power it directly! give it a freewheel and it'd operate exactly like the chain pulling gears on a regular bike's rear wheel.

Also I found a decent drill press on Craigslist for $35 and the fellow is willing to deliver it to my home so I'll be able to do some machining I previously wasn't able to do.

Ugh, it appears the brakes the plans call for are $60 to $100 EACH and I'd have to lathe my own axles...

[TX_Dj]

I'll tell you, drill presses are seriously underrated for their machining capabilities, especially in softer materials. Get you a "machining vise" for your drill press and go to town. It probably won't be as accurate as a proper mill machine, but you may be surprised just how much side load you can put on a cutter before either the head or table turns under the cutting forces.

I used my drill press as a mill for a while until I came up with projects that needed a little more accuracy.

As for the motor connection to the chain drive, I think you're barking up the right tree- but I think you may find you need more than one freewheel (not counting the one on the drive wheel). One at the motor that will cause it to disengage if you're ONLY pedaling, and one at the main pedal crank so that the pedals can remain stationary while ONLY under motor power. Otherwise you end up with your pedals always moving, which of course would give you incentive to always put a little human power along with the motor.

Of course keeping the freewheel at the drive wheel is good because then you can reclaim as much kinetic energy as possible, without waste. If you're going to regen type setup though, remove that, and use an electromagnetic clutch disconnect at the motor instead of a freewheel. This way it can be set to disengage when you're just coasting, and then re-engaged when regen is being applied.

[KrisWood]

The rear wheel would already have a freewheel in its hub (when riding a standard bike the wheel cannot turn the chain), so only one more would be needed at the pulley so that the pulley could turn the wheel but the wheel could not turn the pulley. The pulley is in turn driven by the belt from the motor.

Anyone know where to get stub axles and wheels that are built to accept them? I really don't want to put out a couple hundred dollars for them :-s

[Amberwolf]

Originally Posted by KrisWood

1: Have a combined drive train with an intermediate axle that combines the torque from both the pedals and the motor and then applies it to the rear wheel via another chain.

THis is the best option, as long as you can run the motor at about 80-100RPM max speed at that jackshaft (intermediate axle), so it will match your pedal speeds.

If you look thru my blog or the thread about CrazyBike2 on Endless Sphere, you'll find a few jackshaft ideas plus a little reduction/freewheel device you can make to get the power from the treadmill motor to the main drivetrain. I welded mine, but you could use setscrews or other non-welded means to make yours.


2: Build the pulley from the treadmill into the rear wheel's hub and have the motor power it directly! give it a freewheel and it'd operate exactly like the chain pulling gears on a regular bike's rear wheel.

This will only work if you are running the motor at the lower RPMs, unless you build a reduction stage for it on a jackshaft between the motor and wheel (this is what the bike drivetrain will do for you), to gear it down. If the motor RPM is too low, then you'd need to gear it up instead.

Ugh, it appears the brakes the plans call for are $60 to $100 EACH and I'd have to lathe my own axles...

If the brakes it's using are disc brakes, well, you can easily use regular rim brakes on the single rear wheel, and less easily use them on the front wheels. You could use a steel U fork around the front wheels to mount the rim brakes on, which would also solve your single-ended axle problem, as it would then use a regular one. It would then be possible to mount the kingpin/pivot for the wheel to the inner fork leg, bolting and clamping it on if necessary. Check out the Packrat Workshop for different ways to use U forks on the front wheels.


If you wanted to still use stub axles, you can get light-duty ones from jogger's baby carriages. They are small diameter axles, so they won't take as much weight and may not work for your actual vehicle intended to transport you, kids, cargo, etc, but would work for a prototope testbed. There are some pics in my blog of at least one type; I have another one I can't recall if I posted up or not.

[KrisWood]

Thanks for the feedback Amberwolf! I guess I'll go with the intermediate jackshaft after all. Now if only I had a lathe I could reduce the axle width of the motor to something a bicycle cog would fit on.

By posting on other trike fora I've also learned of another serious flaw in my design; I cannot use wood for the knuckle that holds the axle. It's apparently not strong enough to hold up against the vibrations on the road. I think I'll try it anyway though.

Googling has turned up that the kind of stub axle I need can be found on gokarts and wheelchairs. They are most easily obtained from gokart hobby shops. One person also suggested 14mm BMX hubs as they won't require any modification like a standard 10mm bicycle hub would.