What chair frame or base to launch a custom build?

[flagman1776]

This is such a frequent question, perhaps it should be in the stickies. We've discussed before what chair frame to start from. The Sunrise f55 (which Burgerman used) is a European model with a steel frame. Sunrise Medical, who makes the f55, offers rear drive "S series" models in the USA but I'm told the frames are aluminum. Is an aluminum frame strong enough? (As far as I can tell) the main desireability is to have the frame high enough to clear the oversized wheels. The battery compartment is also the motor mount??? Perhaps it should be considered a sub frame?
There may be other chairs with these attributes, or a skilled fabricator can work his magic.

I did an online search of used chairs & did not find anything else with a high frame, but that doesn't mean they don't exist. Anyone who spots one, please share.

[flagman1776]

Sunrise USA models where the frame is above the wheel (as built) Quicky Models P222SE, S636, S646, S646SE. Although these have anti-tips, they are closer to a RWD chair.

The Invacare Ranger has a high frame but 'as built' the frame is inside & overlaps the tire.

[rustyjames]

The battery box on the 6x6 chairs isn't part of the frame, structurally, it just holds the batteries and the tippers attach to it. In fact, it can be unbolted, only 6 screws attach it to the frame. I'll post more later about this when I can get a chance, as I'm in the process of building one like a BM1 style. I can tell you that it would be major surgery to build one with fat tires/tyres like the BM3, and keep the width at, or below 26".

[flagman1776]

rustyjames, Sorry if I am dense. Which chaisis do you mean when you say 6x6?
If the frame is above the tires (as the Sunrise models are)... & the motors mount to the battery box which is a separate attached part. If we want to mount wider tires & keep the width the same (or acceptable dimension) then the motors need to move in. To move the motors in, the battery box needs to be narrower. With Lithium, a narrower battery box might work.
Am I missing something here?

[Burgerman]

Sunrise USA models where the frame is above the wheel (as built) Quicky Models P222SE, S636, S646, S646SE. Although these have anti-tips, they are closer to a RWD chair.

These?

[LROBBINS]

Except for the P222: the others are 6X6 variants. I think ex-Gooserider has looked fairly closely at those frames, and they would have to be cut and re-welded. TIG is not enough - along the weld line the aluminum will go to T0 state unless heat treated (as someone here pointed out to me when I was designing Rachi's alloy caster forks), so you'd have to find someone with aluminum heat treating facilities too. Ciao, Lenny

[rustyjames]

Flagman, when I wrote 6x6 that relates to the 626, 636, 646 in which they all have the same frame and battery box. The battery box is also aluminum. The motors are swing-arm mounted to the frame, not the battery box. Here's some links:

Frame:
http://www.ebay.com/itm/WHEELCHAIR-ELEC ... true&rt=nc

Battery Box:
http://www.ebay.com/itm/291189942232?ss ... 1423.l2649

[rustyjames]

So, the only way that I can see constructing a BM2/3 type chair would be chopping out those down-tubes that the motors/swing arms connect to, thus eliminating the swing arm suspension, and making a whole new battery box/motor mount assembly.

[flagman1776]

OK so you are counting the anti-tips even though they are pretty far from ground contact.
The various S-series do have anti-tips. http://www.sunrisemedical.com/Products/ ... er/Quickie®-S-6-Series.aspx
The beloved f55 has anti-tips too.
The P222 has anti-tips also. http://www.sunrisemedical.com/Products/ ... er/Quickie®-P-222™-SE.aspx

The Sunrise QM-7 http://www.sunrisemedical.com/Products/ ... eries.aspx with an unknown suspension and Pulse http://www.sunrisemedical.com/Products/ ... er/Quickie®-Pulse™-Series.aspx are true mid drive chairs and certainly the frames are both inside the brghtly colored plastic & between the tires.

I can't imagine starting with a frame that is between the tires, given our objectves of a custom BM1-2-3 clone... Like the former listed products & unlike the later. I am not a welder... so I'll leave that to those who are.

[rustyjames]

The anti tippers on the 626, and perhaps some of the others, were in constant contact with the ground which is quite a nuisance, but that's an easy fix by shoving a bolt in the arm assembly or using smaller wheels (such as roller blade wheels) instead.

BTW: the 222 is a midwheel drive chair, while the 6x6's are rear wheel.

If I recall, the BM1 uses a stock battery box, and the tires are just a bit wider than the manufacturer fitted ones. Eventually, I hope to build a BM2/3 style with a 6x6 frame, but not sure if I'd do the battery box with aluminum or steel.

[ex-Gooserider]

1. I may have been the one that started the Quickie "6x6' label - I got tired of typing 626 / 636 / 646 all the time, so I just used the standard algebraic substitution - as all three models use the same frame in terms of our purposes, it doesn't matter which one...

2. As mentioned the 6x6 frames are aluminum, which essentially means they aren't weldable for all practical purposes. Aluminum loses most of it's strength when welded or heated to close to welding temperatures, and requires fairly complex heat treating procedures to restore it, which is non-trivial for home builders, especially for something the size of a chair frame...

3. In addition, if you look at the front crossmember on the F-55 it is a fairly broad "U" shape that comes down almost vertically and then goes square across the bottom. The 6x6 frame member is more of a 'V" shape where the sides come in at an angle, and has a very narrow bottom section. With the F-55 frame there was room to run the battery box above the frame crossmember as in the BM2, or to cut out part of the frame crossmember and bolt (using some remaining mounting points) the frame to the sides of the box as in the BM3. With the 6x6 frame, the bottom section isn't wide enough to allow the box to pass above the crossmember, and there isn't a good configuration to attach a cut crossmember frame to the box. So it would be hard to adapt the frame to either the BM2 or 3 designs... This is in addition to any concerns about the corrosion potential of mixing aluminum and steel parts, or the strength of any effort to build an aluminim battery box.

ex-Gooserider

[flagman1776]

Thanks, Gooserider. Knowing the obsticles in advance, is what prospective builders need to know, so they can plan.

[Arima]

Reviving this old thread. Has anyone built something with the motors inside the frame using a US frame? There are a couple 646 frames on ebay. If there isn't a suitable frame not sure a RWD is necessary for me at this point. How easy is it to find an F55 with tilt in Europe?

Thxs.

[Burgerman]

Forget f55 as they have not been made for a decade. Use anything you like. Anything similar like an arrow or a bounder, or a pride rear drive chair or whatever. You are only after a starting point. The best chair to mod is likely the one you are sat in. But do it to suit your own needs. You need to know what you are modifying and why.

[Arima]

Forget f55 as they have not been made for a decade.

So I can't have a sexy round ass like you got?

[shirley_hkg]

646 is a very good chair. It has a robust frame and the most sensible suspension layout .

The swing motor bracket can be modified to offset inwards .

[rustyjames]

I agree with Shirley that the Quickie 6x6 chairs are a good base to start with, but I can't agree that the motor mounts can be modified to gain any significant decrease in width of the wheel/tires. There's virtually no clearance between the motor swing mounts and the battery box.

[shirley_hkg]

Shrink the G24 battery box , if going lithium .

[flagman1776]

I haven't looked at the 636 or 646 frames up close and personal but I think I get what he's saying. Since the motor mount arm is a separate piece... it can be removed and altered without messing with the frame itself. I get that there will be interference with the stock battery box, again a separate piece. Maybe the motor mount arm could have a clever mod like being reversed... or maybe reworked or fully replaced.
We need results from some pioneer's build on a S6 series frame.

[ex-Gooserider]

I have an S-626 frame (entire chair in pieces really) that I bought years back and found was not workable to do a BM-x conversion.....

At first glance the 6x6 frames look the same as the F-55, but this is the problem... (as detailed earlier in this thread)

There is a front crossmember that drops down to support the front of the battery box and the pivots for the motor swingarms on both frames.

The F-55 crossmember from photos is essentially a nearly flat bottomed "U" shape... Assuming one does the switch to put the two Group 24 size batteries in line rather than side by side, the crossmember is shaped to either allow putting the narrow box over the top of the crossmember (BM-2 style) or to cut the bottom out and make the box into a frame member (BM-3 style)....

The 6x6 frames have a more tapered "V" shape crossmember - it is to narrow at the bottom to allow a Group 24 size box to fit on top of it, which rules out the BM-2 approach, and since the frame is aluminum, it is problematic to cut and weld to do the BM-3 approach....

What might be interesting and worth exploring is whether the current crop of more compact Lithium cells would allow giving up some of the huge capacity possible w/ Group 24 size boxes in order to make a shorter length box that would fit behind the crossmember and still allow reasonable capacity?

ex-Gooserider

[Burgerman]

You could cut it, and turn 2 round blocks, and drill and tap 3 M8 bolts to hold it in position. With a third tapped hole in the end to hold your new centre section.

No welding needed.

Like this, but with 3 holes drilled and tapped into the sides through the tube of your frame.

[LROBBINS]

And if you wanted that center tube to be lowered, you could attach some 6061 (or 6082) plates, say 6mm or 1/4" thick, to those round plugs (with 2 or 3 screws into each rather than 1 so the plates can't turn). Or TIG the plates to the plugs.

[shirley_hkg]

Now I see the most difficult part is that no motor will be short enough to fit behind the V shape structure, not the motor bracket .


The other candidate is Permobil Street , which inspires the WillChair .

[shirley_hkg]

[flagman1776]

So how do you get the clearance to run wide tires on the Quickie 6x6 series?

[expresso]

you dont - just use 350-8 tires and your good to go - unless of course you want to work - then feel free to cut weld swear - drink - years later - no difference

[expresso]

Happy new years


was meant to be a Joke -

[flagman1776]

expreso, your point is well taken.
The tire sidewall clearance to the motor housing is probably the issue in tire swaps. New hubs / spacers / wheel off sets might let bigger tires be mounted, but also make the machine wider. The fix would be in changing the pivot mounting for the motor swing arm assembly.
To run wider tires without making the machine wider, as bergerman did on the F55 base, by moving the motors inboard. The F55 motors mounted to the strong battery box which is essentially part of the frame at this point.
One could possibly convert the motors to battery box mounting, disgarding the swing arm completely. Or build a new mount for the swing arms. These options take this into a major project build.

I'm going to agree with expresso, that a simple tire swap ought to be part of a first build before going off afield..

[shirley_hkg]

Most chairs can take 3.50-8 tyres without modification, though a little touch on the fenders might be required sometimes. They look much better too.

[flagman1776]

That most chairs will take 3.50 x 8 tires is useful to know. THX.