Because its just a quick and easy rebuild/repair/refresh of a BM2. For a spare chair. Same everything as before other than rims and colour, and replace the hopeless lead bricks with lithium and new bearings, bolts, rose joints, same EMD motors since I already have a new set and they just bolt on, upholstery etc. But yes 6mph is slow! But it wont cost much. Take some pics, test, throw a sheet over it and park next to the fridge!
My next lithium roboteq BM4(X4) chair will be 4x4 skid steer since theres enough power and battery to make it actually work! 4 physically smaller 2 pole motors, 36V, 100Ah usable, 6mph motors at 9.5 mph to guarantee good torque etc. It wont do carpets much good but it will allow decent skid steer control and range for the first time ever in a small indoor usable powerchair. And all wheel suspension. Probably with 4x 145/50-8 tyres like this, on over wide 4.5j rims. Here its over inflated. At 15psi they sit much more square profile than this. Ignore lower tyre. Its a "front" tyre and a different size.
These are 14 inch diameter almost. And wide with a slight curved profile at low pressures, so have a low surface loading for the soft stuff, and so should slide sideways easily too on carpets and other surfaces with little effort compared to tall, treaded, normal profile tyres. And because of low profile, wide rim, no sidewal shuffle when zero turning. And tubeless, despite showing a tube here!
http://kauppa.motorpower.fi/images//webkuvat/4000.jpg