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An adult trike that's modified from a std two wheerer
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January 24, 2018, 03:31:17 PM
see dwgs:


* January 26, 2018, 10:23:16 PM
Interesting idea Bob, but I reckon it'd feel precarious without the rider being able to lean towards the inside of a corner.  I've ridden an adult trike configured like a kid's, with two rear wheels.  I felt like it would tip over outwards easily.   I'm also a bit dubious that the front fork of a standard bike could handle that sort of leverage through the axle line.  That aside, nice work on the model and rendering.    BTW, there's  a motor scooter called Piaggio MP3 (Piaggio's an Italian conglomerate that builds Vespa scooters and high-end business turboprop planes) and a Gilera stablemate, both with two front wheels.  The front end's suspension geometry leans the wheels inwards as standard single front wheels do, so the rider leans in as on a standard bike.  They have a button that locks the front end upright when the machine's stationary, at lights and intersections, so the rider doesn't have to dab their feet.  MP3s get great press for grip and handling and especially braking, because they double the front tyres' contact area over a standard bike, but their front ends are built sturdy.   


January 27, 2018, 06:09:43 PM
Granted, I didn't go through the loading numbers used in a free-body diagram because the material used on a bike axle is of a proprietary alloy and after hardening who knows what you'll be looking at I suppose I could wok the problem backward solving for what is needed for an axle.  It was interesting exercise nonetheless.


« Last Edit: January 27, 2018, 06:26:25 PM by Bob »


January 28, 2018, 03:25:40 AM
Hi Bob,

    nice work, and a well presented concept.
    However, it looks like work in progress, and there's nothing wrong with that!

    Thank you for the MP4 - at least we know it works in a straight line!  ;D

Regards Tim

You can design without engineering, but you cannot engineer without design.
Using Win 10 with Designer 2017 and TurboCAD Pro. Plat. 2016/2017/2018 + Lightworks (64-bit versions).

January 29, 2018, 06:28:59 PM
I went through the numbers for a free body diagram and getting 48 LBS on each front wheel & 114 LBS on the rear for a 210 LBS rider, this is predicated on a CG located about 8” forward of the seat.  This estimate could be validated with a bath room scale under the front wheel and load it with a 210 driver (like me).  What I’m not sure of are you to use the hypotenuse or the cosine in this app., so used the lesser being more conservative.

I added press fit radial needle bearings sized for the .375 shoulder bolts and thrust bearings at key points as the prototype needed that to avoid mild “binding”.  The gap between the two extrusions control turning radius, mine is for a 45° swing right or left.


January 29, 2018, 06:50:02 PM
The numbers in white are weight & in red are dimensions to CG.