MK 3 Version - A Unique Compact FAST Powerchair! 15 MPH

Part 1 2 3 4 5 6 Brochure! & Controls

Mk1 | Mk2 | Mk3 versions + Timeline

The previous page 1 shows a few components gathered together to build this superior fast powerchair.

This page shows a few more! Rather than buy a used donor chair to cut up as I usually do, I bought just a main frame, and a basic seat frame. And the caster forks. The ONLY parts of the donor chair I actually use. And these parts are modified too as you will see.

The main frame for e.g. has to have a chunk cut out to allow me to fit my new longer thinner battery and motor mounting "part" or rather a complete fabricated centre section  This allows me to fit three batteries and my bigger faster motors and STILL keeps total powerchair size exactly the same as the tiny Mk2 version.

This allows the motors to be moved inboard, and the batteries to be turned around, and lithium batteries fitted longitudinally. Target width is still just 25.5 inches or less. Even with 12 inches of fat all terrain tyres. So that it is STILL compact and BETTER indoors than other less capable commercial hi-end powerchairs.

With that in mind I cut 179mm out of the used frame as seen in the following image.

Freehand but carefully measured! 179mm to allow 1mm of filing to correct any inaccuracy. Nice colour! Soon be powder coated black...  I can cut straight. Most people cant so the bit below had some tape wrapped around it as a guide. I only did the first cut. My carer Brain did the second one...

Done! This gap will be 181mm once tidied up. Why? Because that's the width of the battery, metal sides to the battery box to be fitted, allowing for some free clearance, that I will make next!

How do I design the new centre section? Well its not going to be made from wood!

I think very carefully about the exact motor positions, how they will attach etc and required strength, as well as where the C of G will finish up. I look up the total MAX battery dimensions and weight of the lithium pack I will be using.

Other way around!

And I need to keep the caster wheels from hitting the new centre section, as well as the total wheelchair length as short as possible. (about 35 inches including footplate) And total width down to 25.5 inches or less INCLUDING the fat off road tyres to be used. So what looks like a simple thing actually really isn't... Its a lot of extremely careful juggling of figures in my head. And as a proof of concept its easier to build a simple ply mock-up to be sure I am happy with everything. E.G. the rear anti tip wheel height, was just changed too allow wilder wheelies! 

OK that took hours... Now I just need to order some 4mm steel and TIG weld it all together. Actually I just gave the plywood model to my local engineering shop with a full page of measurements to copy. Since I wanted two making and its hard work if you are doing this in a bedroom!. Remember its always cheaper and faster to do two at once. It is almost as cheap as doing just one.

OK two centre sections done! Not bolted in but propped in place here badly!

Total width 25.7 with these tyres. And 25.25 with the 145/70 - 6 all terrain tyres.

Motor angle. Well almost this is just stood here on my bed and a drink can! But you get the idea.

From another angle.

There will be a steel block mounted by bolts or welded to the side here for strength.

For anyone following this build here are some beer mat engineering drawings for some more parts required.  I am building 2 chairs so there are double the quantities you will need here! Parts

More soon!.

Part 1 2 3 4 5 6 Brochure! & Controls

Mk1 | Mk2 | Mk3 versions + Timeline