caster size????

[ex-Gooserider]

I figure that if I'm going to put new tubeless tires on the front of my project chair, I ought to upgrade the front casters as well...

The fork appears to be an Invacare 'shock absorbing' model, not terribly different from the "Frog-Leg" versions.

I pulled the existing wheel which has no visible markings on it, and measured...

The axle is a - 7/16-20 x 4" bolt

The tire is 2.22" Wide and 7.5" Outside Diameter. It doesn't appear to be significantly worn, although the 'hospital grey' is more like 'hospital green'...

The Caster fork MIGHT allow a 2.75" Wide tire, but not more (2.5" max width would probably be better) Max OD would depend a bit on the tread profile, but probably not more than 7.75 - 8"

The wheel is split, fastened together with 4 1/4-20 x 1.25" Flat-head bolts + nylocks. It has a solid tier but might allow a tube to fit?
Material looks like some sort of black plastic. Fairly ugly, but tolerable....

With the tire off, it is 1.25" between flanges, and about 3.65" bead seat diameter. The inside is curved so hard to get an exact number....

What size does this translate to, and any suggestions on best tire / wheel to replace it with?

ex-Gooserider

[shirley_hkg]

This is the best you can get from this suspension fork . Trust me .

[ex-Gooserider]

Definitely looks like the same fork that have on my project chair...

I might get a LITTLE more room since I moved my casters to the lower pair of bolt holes, but definitely a nice fit....

However I couldn't read the tire size in the photos you posted -

So what size ARE the tires in your photo?

Do you have any links to nice looking replacements?

ex-Gooserider

[shirley_hkg]

I might get a LITTLE more room since I moved my casters to the lower pair of bolt holes, but definitely a nice fit....

However I couldn't read the tire size in the photos you posted -

So what size ARE the tires in your photo?
ex-Gooserider

If you think the other hole is meant for different tyre sizes , you are wrong then .

You'll find the chair is hard to steer , especially to stay in course during top speed , as the geometry is totally wrong , being too close to the vertical stem axle . Again , trust me .

Only the KENDA brand will fit , as it is a bit under-sized .

Forget the plastic rims and get substitute , best with independent barrel with split halves like the one in photo .

[shirley_hkg]

I insist on this bearing barrel with mounting plate in one-go design , because it is more robust .

As BM advocated, it's simple physics .

Others have split halves went with a barrel half .

Sadly it don't come with under-sized KENDA tyre, so has to purchase seperately .

[ex-Gooserider]

That's OK, I'm sure I can find the Kenda tires, once I have the casters to put them on...

ex-Gooserider

[shirley_hkg]

I can get you 4 KENDA tyres as well , and they are definitely cheaper than being bought your end .

[shirley_hkg]

This is gonna be a perfect fit , 72mm wide .

Your suspension fork is 73mm inside .

Shiny polished .

US $5.80 a piece .

[ex-Gooserider]

Just saw this - after our messaging about the stuff I was getting and my sending you payment -

Are these the ones you are getting me, or the ones from the earlier post I was pointing at? I'd prefer these, as they look a lot nicer, but am OK with either...

BTW, any guess on ship date? I assume you need to get them on your end, but how long does that take?

ex-Gooserider

[shirley_hkg]

Just saw this - after our messaging about the stuff I was getting and my sending you payment -

Are these the ones you are getting me, or the ones from the earlier post I was pointing at? I'd prefer these, as they look a lot nicer, but am OK with either...


No. I bought you the steel ones because I think they are more robust .



BTW, any guess on ship date? I assume you need to get them on your end, but how long does that take?


ORDERED . Will collect all of them in a week . Then , have to wait my wife to lend her hands to re-pack everything .

[shirley_hkg]

Caster arrived . Looks very robust .

Have to trim the barrel a bit to fit 73mm fork's 73mm width .

[Furio]

Has anybody come across nylon wheel rims for 3.00-4 tyres ? I want replace my aluminium caster wheel rims as they get corroded fast even after powder coating. Any information will be appreciated. Thanks.

[Burgerman]

You want primo or mbs wheels...

http://www.trampaboards.com/9-inch-wheels-c-298.html

https://www.mbs.com/parts/
https://www.mbs.com/parts/13017-complet ... by-wheel-1

https://www.atbshop.co.uk/mountainboard ... ies/wheels primo

[ex-Gooserider]

OK, not in a panic about it, but just like to know when to expect the UPS guy...

Not a problem with the casters - we have several lathes at the Asylum, just takes a few minutes to face off the barrels...

ex-Gooserider

Just saw this - after our messaging about the stuff I was getting and my sending you payment -

Are these the ones you are getting me, or the ones from the earlier post I was pointing at? I'd prefer these, as they look a lot nicer, but am OK with either...


No. I bought you the steel ones because I think they are more robust .



BTW, any guess on ship date? I assume you need to get them on your end, but how long does that take?


ORDERED . Will collect all of them in a week . Then , have to wait my wife to lend her hands to re-pack everything .

[shirley_hkg]

I did just start looking at the caster wheels I got from Shirley, and am seeing a LOT of issues...

The wheel itself looks nice, gold cad? plate steel, but the bearings are mounted in the center hub with no spacer in the middle (bad for ball bearings like these that get side loads when turning...)

The bearings themselves are steel 6202Z - metal shielded rather than rubber, which isn't a big deal...

Another annoyance is that 3 out of the 4 bolts on the one caster I've taken apart so far were over-torqued to the point of thread damage, about 1/2 turn from being stripped.... As far as I'm concerned, that means needing to replace them...

I also notice that the bearings are not inserted to a uniform depth, or apparently against the ridge inside the hub... The first wheel showed depths from the edge of the hub to the bearing 0.084" / 2.15mm and 0.161" / 4.10mm. The second wheel had depths of 0.107" / 2.72mm and 0.168" / 4.27mm... I tried pressing the bearings in further with a bolt and some flat washers, got a good bit of movement - and now show 0.170" / 4.33mm on both sides.... Poor QA on assembly, but fixable...

However what is a significant issue, is that the hubs are longer than the forks are wide... My caliper says the hub is 3.060" / 77.68mm wide, while the fork is only about 2.965" / 75.33mm between the legs....

I also subtract points for not cleaning the welding splatter off the flange before plating it...

Unlike the rear wheels or the power supply, these seem like rather a poor quality item overall... I can make them work I'm sure (as BM says, it's just metal...) but it will take a good bit of work...

Shirley, I believe these were supposed to be the same wheels you used on your chair? If so, how did you adapt them?

Did they fit inside your forks without being cut down? Or did you cut them down or spread the forks? (they seem like a heavy casting that would be hard to spread...)
Yes, I have to trim off the excess barrel edges , and fit EVERYTHING within 73mm. Hope you don't have to move the bearings further inwards to get there. However, it's not a bad thing to move bearings a bit inside , so that you will gain more room to accomdate everything .

''' Keep everything within 73mm , NOT 75mm . '''


I also noticed the end of the valve stem sticks out past the rim - does it clear the fork?

A narrow escape WITHOUT cap .


Unless there are other suggestions - it looks like what I will need to do is:

1. Get a better set of measurements on how centered the hubs are in the wheel and take a total of about 3mm off the ends, keeping the wheel centered in the fork.

2. Make a center spacer - presumably around 0.75" / 19mm OD, with a 15mm step down on each end, and a 7/16" bore (the stock axle diameter) and put it in while replacing the bearings.
Good point , though I don't have it .


3. Make end spacers to fill the gap between the bearings and the outside of the forks - I'll probably try to make something that is a fairly close fit to the recess in the hub just to try and minimize the 'furball' buildup... So about 34mm OD, with a narrow 15mm step on the inside and a 7/16" bore...
Only 1mm thick due to limited space . Therefore, it's not a bad thing to move bearings a bit inside , so that you will gain more room to accomdate everything .




Do you think aluminum would be OK, or would I need to try doing stainless?
I used to diy them from hard plastic rod and everything survived , though all are steel now because my machanic likes steel .


Shirley, does the place you got the caster wheels from have any dimension drawings by any chance? I can do my own measurements (and probably will regardless) but having manufacturer specs would be good as a double check...
No , and every lot differs .


ex-Gooserider

[ex-Gooserider]

I've done some measuring on the China casters, and while some error may be due to my technique and equipment, I'm also very unimpressed by the lack of precision in these wheels... I just hope that they will be 'good enough' once I'm done with them...

With one end of the hub on a surface plate, and using a dial indicator on a mag base sitting on the same plate, I was getting about a 0.005" variation in the distance to the from the opposite end to the bearing face (AFTER pressing them in with our arbor press to make sure they were fully seated)

It was hard to measure the rim as there isn't a really good reference point, but trying to do the best jig fixture I could, I was seeing about 0.05" to 0.08" side to side runout measuring from the end of the hub on the surface plate - it was repeatable, and both sides seemed off about in parallel....

I will grant that the end of the hub isn't necessarily a good reference surface since it isn't inherently parallel with the bearings, but it seems to me like it would be harder for it to be off than it would to be right...

I did some drawing - jpg attached, I can send .pdf or native .dxf file if anyone wants it...

Yellow is center spacer, red is outer spacer, cyan is hub (left flange off) blue is bearing, magenta is fork, dimensions in inches

Dimensions are inch because that is what the lathe I'm using is calibrated in... I also didn't draw in any tolerance allowances but I can add those as I do the machining... I only drew one of the outer spacers - same thing goes on the other end....

My plan is to make the total thickness enough that I have to slightly spread the fork to get the caster in, but that will make everything snug up nicely, I don't have a direct way to measure the distance between the (poorly finished) bearing seats in the hub, but I have a calculated distance based on the surface plate measurements I described, and I'm making the center spacer a little longer so the bearings outer races may be 'floating' a bit in the hub, but I'll have a solid stack between sides of the fork.

I have some 0.75" stainless shaft - not sure of the alloy, but it is probably 303, which seems ideal for the center spacer, and some 1.25" aluminum round that is a bit undersize but will be OK for the outer spacers (their OD isn't critical as long as it's less than the bearing OD)

Anyone see any glitches or problems in what I'm planning?

ex-Gooserider

[shirley_hkg]

Bear in mind that the mid point is mounting face plus ONE rim half's thickness .

[Burgerman]

I think it will work. But those cheap steel wheels are not very well made and really intended for welding trolley or generators etc. I would have used the plastic or alloy ones.

Like the primo http://www.trampaboards.com/9-inch-wheels-c-298.html
or mbs rims,







With too small tyre...

[LROBBINS]

Been using the MBS wheels for several years on Rachi's chair - good fit and solid construction. Just be sure to grease those stainless bolts so they don't gall to the nuts. Pity they're not tubeless.

[Burgerman]

I have a set of MBS too, and for smaller 8 inch or less tyres http://www.trampaboards.com/hubs-c-50.html?all=1

[ex-Gooserider]

Well I have these wheels, so might as well see if I can make them work...

I've gotten my inner spacers cut and faced so I can start drilling the center holes - which will be interesting in stainless.... However, so far what I've done has gone pretty easily, even with the cheapo HF carbide insert bits I've been using... Supposedly 303, which is what I think this stuff is, doesn't have the same work-hardening issues as some of the other stainless alloys

(I'm assuming it is 303 as it's non-magnetic, and most of the listings I find for non-magnetic stainless shafts are either 303 or 316, with 303 being more common...)

If nothing else, it will be good lathe practice...

[Burgerman]

What's the difference between 304 and 316 stainless steel? The simple answer is 304 contains 18% chromium and 8% nickel while 316 contains 16% chromium, 10% nickel and 2% molybdenum. The molybdenum is added to help resist corrosion to chlorides (like sea water and de-icing salts)

These are the two commonly available in bolts, sheet stock, bars etc. And exhaust tubing, etc.

Never heard of 303? So I did a search.

Alloy 303 is a non-magnetic, austenitic stainless steel that is not hardenable by heat treatment. It is the free machining modification of the basic 18% chromium / 8% nickel stainless steel. Alloy 303 was specially designed to exhibit improved machinability while maintaining good mechanical and corrosion resistant properties Due to the presence of sulfur in the steel composition, Alloy 303 is the most readily machineable austenitic stainless steel; however, the sulfur addition does lower Alloy 303’s corrosion resistance to below that of Alloy 304. Like other austenitic grades, Alloy 303 demonstrates excellent toughness, although the sulfur does reduce this a little as well.

[sacharlie]

I have a set of MBS too, and for smaller 8 inch or less tyres http://www.trampaboards.com/hubs-c-50.html?all=1

Haven't found any tire larger than 200x50 or 200x75 to fit those. The wheels are ~3&7/8" diameter rim.

[ex-Gooserider]

Are there 'very' magnetic stainless steel alloys? I just got in the bearings I ordered for these wheels... I ordered (and paid extra for) SS6202RS bearings, advertised as stainless steel, etc..

The bearings that arrived are KML brand, made in China... They are marked both on the box and the bearing itself as Stainless, but my handy test magnet sticks to them just as hard as one of the old rusty bearings I keep as a spare / driver... They don't appear to be 'food grade' though, as the shields are the same black rubber seen on most bearings, rather than the usual 'color not found in nature' blue of a food grade bearing....

I'm used to some of the stainless steel hardware I use being slightly magnetic, but only about half as much as steel...

If these really are legitimate stainless (and possibly Shirley can comment on whether KML has a good reputation?) I'd suggest the place I got them from as a source for US folks at least - Service was good, website is pretty good for 'user-friendliness" and prices seem better than I've seen anywhere else for (whats marked as) stainless bearings... The place is "The Big Bearing Store" which appears to be a division of Carnell Sales, and is located in Memphis, TN....

ex-Gooserider

[Burgerman]

My blue rubber sheild eBay bearings have no noticible interaction with a magnet at all that you can feel. Neither do the bolts or washers/nuts.

[flagman1776]

I'm looking at Shirley's picture in post #2... the first picture. I'm wondering if the axle hole couoldn't be redrilled further down (to get more tire room) and back "to the right" to get more offset (if that becomes desirable for tracking). It would be difficult to do but might be an option.

[Burgerman]

Or just use a different fork.

And:

However, the most common stainless steels are ‘austenitic’ – these have a higher chromium content and nickel is also added. It is the nickel which modifies the physical structure of the steel and makes it theoretically non-magnetic.

304 stainless steel contains chromium (min. 18%), and nickel (min. 8%). It is an austenite steel and is only slightly responsive to magnetic fields. It also contains 18 – 20% chromium and 8-10.50% nickel, and lesser quantities of some other elements.

316 stainless steel is a molybdenum-alloyed steel. The fact that it is also negligibly responsive to magnetic fields means that it can be used in applications where a non-magnetic metal is required. It also contains a number of other elements in varying concentrations.

https://greenwoodmagnetics.com/resource ... ess-steel/

[LROBBINS]

There are also martensitic stainless steels (such as the 416 that Will Clark used to make a VOCA mount tube for Rachi's chair) that are stronger, but somewhat less corrosion resistent and also magnetic. I don't know how you can tell from the outside whether a magnetic steel is stainless or plain carbon steel. Maybe the supplier can tell you what alloy was used for those bearings.

[ex-Gooserider]

I'm looking at Shirley's picture in post #2... the first picture. I'm wondering if the axle hole couoldn't be redrilled further down (to get more tire room) and back "to the right" to get more offset (if that becomes desirable for tracking). It would be difficult to do but might be an option.

I agree, probably doable, although it might result in being a bit short of 'meat' around the new hole depending on how far it was shifted...

Probably not that difficult either on a CNC mill - biggest challenge would be figuring out the best work-holding setup... I would then zero on one of the existing bolt holes, and offset from there...

I have sent an e-mail to the bearing supply house, asking what alloy they used... Will see what they come back with for an answer... Might also see if KML has an English language website.....

ex-Gooserider

[Burgerman]

http://www.kml-bearing.com/yb/index.php

Doesent matter much. Wipe off oils and grease with some parafin. Kerosine. Or detergent.

Chuck it outside in the wet weather for a week. If it turns red throw it away. If it wipes clean and is as shiny as new, fit it!