What chair frame or base to launch a custom build?

[ex-Gooserider]

The only caution that might be involved w/ switching from the commonly used (at least in the US)3.00 X 8 solids or tubes to 3.50 x 8 is that the several pairs of 3.00 X 8 solids I've measured (all 'hospital grey' Primo tires, which it seems is the standard) come in undersize - closer to a 2.50 or 2.75 X 8 than a 3.0, While the the 3.50 X 8's that I measured were close to nominal.... This means the stock wheel is undersized even more than the nominal 1/2" / ~6mm difference in nominal sizes would suggest...

This seems likely to cause suspension issues on a mid-wheel chair as the height of the chair at the drive wheels is increased, while not changing the caster height, so it MIGHT do odd things to the suspension operation, starting with making the chair more prone to the fore / aft rocking that the mid-wheel design is supposed to prevent....

On an RWD or FWD chair you will get a slight change in seat angle, and the caster stems might be shifted far enough from vertical to cause steering issues, I'm not sure...

It is also worth noting that since one can run a tubeless tire soft, it may squish down enough under load to eliminate some of this difference that I get measuring the wheels on the bench...

ex-Gooserider

[Arima]

I am so far behind you guys not sure I'll ever catch up. The plugs are a neat idea!

Keep reading this forum expecting it to all start making sense but it hasn't happened yet. Are brushless hub motors an option? Just talking out loud I think a new battery carrier making the connection to the frame and the lower front frame member. Mount hub motors to the battery box. I must be missing something cause you people have already considered this I bet.

[Arima]

Giving up some range due to a smaller pack might make one of these project easier.

[Burgerman]

Quite the opposite.
It means you need to keep track of cell discharge level. Be sure of never running too low and that all cells are capacity balanced so that you dont run one low suddenly. Because you only go below 2.5V on one cell, once and its knackered for good.

Also, running a smaller pack means you lose out on the biggest advantages that makes it sensible to do in the first place.

You lose out on:
Huge range
That thing you dont realise you are suffering from till its gone RANGE ANXIETY and it frees you to go anywhere, anytime.
Battery longevity and reliability. These things CAN last a decade or more. If you dont fit a small pack.

A small pack gets discharged more deeply, and recharged daily.
A large pack gets discharged very little (increases cycle life) and can be recharged once a week in winter if you dont go far. So it has maybe double the cycle life, and these cycles are weekly not daily...
And a small pack gets a higher discharge rate per Ah (more Amps per cell) which lithium hates. So to minimise damage a higher rate cell must be used, which are more expensive and/or bulkier meaning less Ah in the same space.

So small packs dont make as much sense. You may as well use a set of MKs. Because you are throwing away the lithium advantages, which allows much more Ah to fit the same space.

[Burgerman]

I must be missing something cause you people have already considered this I bet.

Yep, bad plan. Details are complex, and will take me pages... Theres no good solution that way. At least not one thats not seriously complicated and $$$ and not without a gearbox.

[flagman1776]

I did a small pack as that is all my Travel Scoot takes BUT I was fortunate to discover the superlight weight scooter really wasn't bad on batteries. I agree with BM though, building a "right size" pack is the way to go today. There are cells available now that will build a right size pack to replace the Sealed Lead Acid batteries chairs come with, right in the OEM battery box. The cells you want are LiFePO4 chemistry. Assembling a pack is not that complicated. A bit of wiring.
We will help you. The people here helped me.

Beyond the pack, you'll need a Smart Charger. Currently the best charger is the Cellpro PowerLab 8. (abbreviated PL8)

To run the PL8 you will need a power supply. You can get a fancy multi feature power supply or and simple one based on an industrial server supply.

Yes, again, Bergerman is right, the total joy of the right sized battery pack is you don't have to worry about running out of power and being stranded somewhere.

This thread was intended for the novice about what current chair to start with to do a "Lithium conversion" on.

[Arima]

I'm a long way from actually doing anything toward a custom build but it's not hurting to dream. After rereading everything 3-4 more times a power supply seems like a good next purchase. Hey the Lithium conversion thread is only 182 pages lol. The next question to answer is what are the advantages of a switchable supply or a linear supply. And what exactly do you program on a programmable supply.

No argument regarding a smaller pack....that's something I need decide for myself. As Burger said Mk's might be the right part for the job. Need to slow down spending after the holidays.

[LROBBINS]

I highly recommend the ZDS power supply (that Shirley in Hong Kong has volunteered to supply). It is stable, easily set up as a straight, adjustable output supply (for PL8) or as a 3-stage charger (for lead acid). It can be set to any voltage up to 60V and controlled current output up to 50 A. It's one fault is noisy fans, but I replaced them with low-speed, thermostatically-controlled fans and it is close to silent - completely hidden by ambient noise when placed on floor next to the chair. For now, using it for Pb via an Anderson SB50 installed in the case and it's set up so that it's a one button operation: push to turn on. Don't even need to turn it off as I've set it to auto turn off if current flow in float falls to <0.2A for 1 minute. It is well protected internally so there's no need to worry about connection order - connect to chair then turn on, or turn on then connect to chair work equally well.

[flagman1776]

A Lithium (LiFePO4) conversion is not "cheap" but nothing worth while is. You match the scooter or power chair's original "24" nominal voltage. The devise doesn't care where the power comes from so long as it's within it's tolerance.
Lead Acid Battery technology is not improving, the science is complete... Quality is generally declining as manufacturers try to pinch every penny. Used hard SLA batteries have a one year life.
LiFePO4 has huge longevity. They lasts so well, we don't really know how long they'll last. My pack is 8 years old and still running. LiFePO4 quickly pays for itself but more importantly allows a fuller, more active participation in life.

[Irving]

A Lithium (LiFePO4) conversion is not "cheap" but nothing worth while is. You match the scooter or power chair's original "24" nominal voltage. The devise doesn't care where the power comes from so long as it's within it's tolerance.
Lead Acid Battery technology is not improving, the science is complete... Quality is generally declining as manufacturers try to pinch every penny. Used hard SLA batteries have a one year life.
LiFePO4 has huge longevity. They lasts so well, we don't really know how long they'll last. My pack is 8 years old and still running. LiFePO4 quickly pays for itself but more importantly allows a fuller, more active participation in life.

Your opening statement is incorrect... a LiFePO4 conversion is cheap, it just requires an up front investment. If you look at the future value of that investment taking into account inflation and the likely future replacement cost of SLA batteries then, even without all the other benefits, its a no-brainer.

[Burgerman]

If you compare only Ah per Ah, and decent lead like MK gel, or Odyssey etc, then its ALREADY a CHEAPER initial outlay!

The only reason its more expensive initially is that you buy MORE Ah to go in the same space your lead comes out. To maximise longevity and range and make the best advantages of the lithium technology.

Its like comparing 10 gallons of fuel for your car, to 2 gallons... Obviously 10 gallons is more expensive. Even though lithium is already cheaper price per gallon.

Even more so when you consider that every lead gallon you buy is only really half a gallon! A 40Ah lithium will take you as far as a 70Ah MK Lead. And its cheaper. But it will not last longer, and it wont give more range. But it wont cost you more! But it doesent make any sense.

[shirley_hkg]

Also note that 50% of your money went shipping.

LiFePO4 is way cheaper than MK, no matter in any senses. Lithium_ion is even cheaper.

[Arima]

it's set up so that it's a one button operation: push to turn on. Don't even need to turn it off as I've set it to auto turn off if current flow in float falls to <0.2A for 1 minute. It is well protected internally so there's no need to worry about connection order - connect to chair then turn on, or turn on then connect to chair work equally well.

Thxs...this is an example of programming the power supply? I've seen a couple threads mentioning the Shirley supplies. Will have to go back and review those:)

[LROBBINS]

All of the programming is done with a single rotary encoder/push button with on screen cues. At a minimum, you just have to say Yes or No for several options-allow 3-stage charging, allow auto start when plugged in, allow auto stop at low current flow. Beyond that there are settings in an EEPROM menu for setting max volts, max amps, temperature/fan profiles. In first normal use or if you change what you're using it for, you just set volts and amps, turn on or not 3-stage (setting float volts and switchover current if the auto settings are not appropriate), etc. After that it's just push once to turn on and that's it. It takes a while to read through and understand the instructions - Google translate hasn't done a perfect job going from Chinese, but not all that bad either. There are links to those instructions at several points in the main thread.

Probably more work than setting up a plain-Jane fixed power supply for the PL8, but I think it's more than worth it. And you get an industrial quality unit at a reasonable price thanks to the sanctions on Iran blocking shipment of a massive number of these.

[ex-Gooserider]

While I totally agree with the recommendation of the "Shirley Supply" it is worth noting that unless one makes unusual efforts to connect to a 220V outlet, it only does about 22A out when used here in the US on one of our standard 110V outlets.... Still nothing to complain about! It is enough to power a PL8 to reasonable levels, and more than enough to charge lead bricks.... In practical terms, you are going to have some difficulty finding a supply that runs on 110V and puts out more power w/o regularly blowing fuses....

In terms of switching supplies vs. linear - Linear supplies are basically transformer based units, and are generally considered obsolete by modern standards, as they are big, heavy, waste a lot of power, and have an output voltage that varies unless extra effort is spent on power regulation....

Switching supplies use electronic circuitry to do the power conversion, and as a result are lighter, smaller, MUCH more energy efficient, and have much better output regulation... These days I would never even consider purchasing a linear supply, and would probably not even pick one up as a freebie....

ex-Gooserider

[Arima]

Thxs guys...I have a dryer outlet:) One of the ads for a linear supply included a usb port and pc software. Sounds like same stuff you do with your dial.

[Arima]

Does anyone have an opinion regarding Kymco K-Active rearwheel drive chairs? This might be a better frame to start a build than say a quickie 646. Looks like a Euro only product not available in the states as far as I can tell. Wonder if anyone in the US has purchased a Euro chair and had it shipped to the states.

[Burgerman]

Its chinese.

[Arima]

Its chinese.

LOL..I guess that says it all. I see them advertised thru http://www.themobilityaidscentre.co.uk and a few other sites ending in uk...so I thought they were Euro. Thought the Chinese only made folding electric chairs. £1,895.00 is well under 2000 us dollars plus shipping. The problem is rear wheel drive chairs are not abundant here in the states.

[Burgerman]

I know. And it baffles me. Last april I had all my rear drive chairs, 2 mid drives here, and a front drive. I used them all to see if I could give them a fair comparison.

Mid? You gotta be joking. Too many wheels, Whichever way I turn or manoever something always hits the walls, furniture, etc. And they are all longer than my own rear drive chairs. Horrendous ride with most of your weight in the drive wheels with no suspebsion, and some on those arms that have tiny casters that transfer every shock. I got stuck before I left my house on the lawn because it was wet (it rains here) and soft. I made the fatal error of reversing.

Front. IF you get pnumatic tyres, and IF its got adequate torque (120A 4 pole) and IF programmed well (not easy as the essential gyro takes away your control input when it needs to do so for straight line stability) they are good at curbs. But why do you actually need to go up curbs? Theres always curb cuts, drive ways, or low curbs any chair can drive up anyway. They handle weird once programmed to respond properly. That alone is a deal breaker. But worse I go to many pubs. They take out people feet as the rear swings around as you try to manoever at the bar or to turn in place as people naturally pile in behind. It could get you killed in some of the places I go! No thanks.

Over the years I tried many. Basically all front drive are the same. Same with mid drive. And STOCK rear drive chairs are all the same and useless too due to inadequate torque and too forward CG and often stupid swing away footrests... So choose with care!

But the best by far once SORTED OUT is the rear drive, with the correct options, centre footplate, seat and CG moved back, and reprogrammed to respond. You cant fix the issues on F and M chairs.

[Arima]

Posting this as a reminder to myself...or for discussion. I only see 2 basic designs...a tubular frame or a box. One element I like is narrowing the frame to tuck tires within the boundary edge of the seat pan if you have a seat pan. The folding frame pictured means you would not need to cut to narrow it. Obviously the frame shown is much lighter than the average power chair and there is still a ton of bracing fabrication and detail to be engineered. Just a half baked brain fart I have not thought through.

One huge challenge is determining my needs...trying to build one chair to do it all is to really hard for me to think about. Everyone has unique needs...this would be an indoor chair that doesn't scare people from getting near you. Would be nice if it could go to the mall I suppose...and drive from the chair. Something like the lightweight Hawk or Eagle folding chairs which also interest me.

What would happen if you bolted some lighter 2 pole motors with a gearbox to a frame like this?

[Burgerman]

You would get a weedy chair with little torque, zero suspension, the rear would be way too low, front casters will snag and bounce off every edge and jam in every place they can as you drive till something breaks. And you wont have space for big enough batteries. By the time you fixed all the problems, it willlook like all the other powerchairs do. Guess why they look that way.

Thats what they did in 1950. Then they adressed all the issues over the years...

[steves1977uk]

Heh, I remember those BEC chairs from my schooldays in the 80s! They were a harsh ride to say the least!

Steve

[Arima]

Okay so tube frame is preferred to a box. In case we need a tilt version. I'm sure you're right about the casters.

[ex-Gooserider]

Obvously never had my hands on one, but the earlier question about the Kymco chairs seems to me that it wouldn't be a bad starting point just looking at the pictures... They look sort of like a clone of the F-55 or 6x6 series chairs with a frame that runs above the drive wheels - which might make them easier to move inboard as done with the BMx chairs.

No idea if it's the same outfit or not, but Mary-Anne found a similar looking "Heartway" chair out of a place in FL, US - However it appears that the US seller has either gone out of business, or just sells scooters now...

But I did find what appears to be the same company as the Taiwanese (whether that counts as "Chinese" is a question of political opinion....) manufacturer http://www.heartway.com.tw/product/power-wheelchair/rear-wheel-drive Their HP-7x series looks pretty reasonable - there were a lot of other RWD models as well, some of which looked rather odd, others fairly decent...

No idea if available in the US or elsewhere, or how 'reputable' they are but....

ex-Gooserider

[Arima]

I'm just trying to get a list of possible starting points. Permobile 350 also comes in rwd I believe. Looks very much like the "Street" version. Also Quickie P190.