New Tyres on my Puma 40

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Re: New Tyres on my Puma 40

Postby shirley_hkg » 05 Jan 2019, 09:38

ex-Gooserider wrote: The stock wheel is a 3.0 - 8 tire, the new wheels use a 3.5 - 8 tire, so nominally 1/2" wider... (measured - stock is about 2.75" wide, new wheel is about 3.75" :thumbdown: - so much for nominal sizes....)

I
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Trim the 82mm hub to 75mm.

Weld a new mounting plate to the back of above . Machine it to fit and sit on the edge of above .

A few mm can be gained by moving the fender inward and upward .


Guess your stock wheels are under-sized grey flat-free knobby tires , not pneumatic.
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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 11 Jan 2019, 05:55

shirley_hkg wrote:
ex-Gooserider wrote: The stock wheel is a 3.0 - 8 tire, the new wheels use a 3.5 - 8 tire, so nominally 1/2" wider... (measured - stock is about 2.75" wide, new wheel is about 3.75" :thumbdown: - so much for nominal sizes....)

I
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Trim the 82mm hub to 75mm.

Weld a new mounting plate to the back of above . Machine it to fit and sit on the edge of above .

A few mm can be gained by moving the fender inward and upward .


Guess your stock wheels are under-sized grey flat-free knobby tires , not pneumatic.


Right on the tires - sidewall says 3.0, but caliper says different... As I said, so much for standards / nominal sizes...

The trimming approach was one of the ideas I came up with first, I'm just wondering if the idea of flipping the hub 180* and building out from the back might be simpler / easier - though it seems that either way amounts to about the same thing....

I also need to find a spare hub / wheel of some sort that I can put on the chair just to be able to roll it around if needed while working on the mod....

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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 11 Jan 2019, 06:26

Burgerman wrote:Not sure. But I figured out that the thinner rims and 3.50 tyres would be a pig to fit long ago. However you do it you end up with a not very elegant solution. Its why I used the taper-lock hubs on the old BM1 chairs. And the 3.5j rims and 120/70 tyres on the salsa. Because the motor shaft is too long for aftermarket skinny wheels. They have zero offset. You end up with the wheel having a nut or flange poking through.

You can do it with a set of these with the correct taperlock size for the shaft.

https://shop.eriks.be/en/mechanical-pow ... aper-bush/

Its what holds these on... http://www.wheelchairdriver.com/images- ... re-450.jpg


Interesting link, though I have to give that site a total fail on user helpfulness - it just shows a list of part numbers, but no explanation about what they are describing, and every item has the same picture... I tried downloading their 'overview' and it was also pretty useless - the same picture of a bunch of different parts and their letter head.... I did finally find Optibelt's website, and catalog, which seems fairly useful...

I am also finding a lot of US sites for taperlock stuff - but am having trouble figuring out how to understand the part systems... They seem to have several different variants on the basic idea, and none that I've found so far make it clear about how to find the right parts....

If I recollect your build notes, you turned v-belt pulleys down to make flat mounts, mostly because that is what you had in your parts stash...

However if starting from scratch, do they make (and would it be better) just plain flat plates that can be drilled for mounting?

I'd also note that the stuff I've seen prices on - a lot of places didn't show pricing - seems like the taper-locks are VERY expensive - unless I'm looking at the wrong things...

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Re: New Tyres on my Puma 40

Postby Burgerman » 11 Jan 2019, 11:02

I used the rusty ones on my bench.
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Re: New Tyres on my Puma 40

Postby woodygb » 11 Jan 2019, 22:49

http://www.bearingshopuk.co.uk/belts/taperlock-bushes/

The taperlock BUSH comes in a SERIES size and each SERIES covers a range of shaft diameters....
TAPERLOCK.png



You pick the requisite housing that matches the SERIES.
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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 14 Jan 2019, 06:52

woodygb wrote:http://www.bearingshopuk.co.uk/belts/taperlock-bushes/

The taperlock BUSH comes in a SERIES size and each SERIES covers a range of shaft diameters....
TAPERLOCK.png



You pick the requisite housing that matches the SERIES.


Thanks, Woody, that helps clarify what I'm looking for a lot.... :worship

The website you pointed at makes more sense than most of what I found so far - at least for the bushes - I now need to find a housing that works (which then goes back to picking the bush...) czy It also seems like more reasonable pricing - though I would think I'm better off going through a US based vendor just to save on shipping....

I've been taking it a bit easy the past few days as I just had carpal tunnel release surgery on my left wrist Tuesday (they used the latest high tech 'minimal invasive' techniques - turned out to be much less of an ordeal than I was afraid of but I'm still a bit sore...)

However I got the hub off just a few minutes ago - it mikes to 0.750" / 19.05mm - not sure it makes much difference being that close... For whatever it's worth, the nut that held the hub on is 1/2-13 so I figure the shaft is also likely to be inch...

What I'm finding on the bearing shop site are either pulleys or sprockets.... Presumably a sprocket might be easier to machine if it is thick enough to support the wheel mounting screws since it should already be flat, and just need to have the appropriate holes drilled and tapped (might or might not need to / bother taking the teeth off...) A pulley might also work, but presumably would need more machining to get a flat mounting surface...

I think I need at least 1/4" - 6mm of thickness for threads, more might be better... Looking up chain specs suggests that would be a minimum of 5/8" chain pitch - I am not sure how big a pitch diameter for the sprocket I'd need to have enough space for the 92.5mm PCD of the wheel - but there seem to be plenty of choices... The other thing that isn't obvious from the description is which end the bush goes into????

Getting the existing hub in my hand lets me get a bit better measurements off it - It looks like I have about 2.25" / 57mm between the mounting face of the hub and the end that hits the step on the motor shaft.... From the measurements I took earlier, that suggests I need the new mounting face to be about 1.5" - 1.75" / 38-45mm from the step.... Assuming that the mounting face is flush with the end of the housing, and that the bush fits flush with that, it looks like I'd be OK with any of the listed series except possibly the largest ones...

But at least I feel like it's making progress...

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Re: New Tyres on my Puma 40

Postby woodygb » 14 Jan 2019, 10:38

Be aware that you must choose a sprocket or pulley that is "handed" in relation to the direction that the taperlock is inserted and done up.

Most sprockets have the taperlock inserted like this...


Image
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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 15 Jan 2019, 03:42

woodygb wrote:Be aware that you must choose a sprocket or pulley that is "handed" in relation to the direction that the taperlock is inserted and done up.

Most sprockets have the taperlock inserted like this...

Image

:cussing :cussing That would be the 'wrong' side for what I had in mind... But might still work if I have enough shaft length, and pick a housing that has a diameter smaller than the 75mm hole in the center of the wheel...

However I'd think it should be possible to find a housing that fits the way I want - or possibly something I can bolt a flange of some sort onto....

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Re: New Tyres on my Puma 40

Postby woodygb » 15 Jan 2019, 21:21

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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 17 Jan 2019, 04:51



Really interesting link Woody! They didn't seem to have anything that matched the China wheels exactly, but were close, especially the second link... I could probably make that one work by drilling new holes, or possibly replicate the design on one of our mills. (it looks pretty simple....)

I did discover something a bit odd about the China wheels though - I'm not sure if it is anything to worry about or not... I was checking the size on the bolt holes, and found that both 5/16" and M8 bolts were a loose fit in the holes, but 3/8" and M10 definitely would not fit... The wheels weren't countersunk to fit a conical lugnut / bolt the way most car wheels are either. I am wondering if I'd get slop in the wheel centering if I just used straight bolts?

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Re: New Tyres on my Puma 40

Postby woodygb » 17 Jan 2019, 09:06

Centering is usually achieved by using the large hole in the middle of the wheel hub....thus the slop in the RETAINING bolts doesn't matter.
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Re: New Tyres on my Puma 40

Postby Mechniki » 17 Jan 2019, 11:18

ex-Gooserider wrote:


Really interesting link Woody/Goose! They didn't seem to have anything that matched the China wheels exactly, but were close, especially the second link... I could probably make that one work by drilling new holes, or possibly replicate the design on one of our mills. (it looks pretty simple....)

I did discover something a bit odd about the China wheels though - I'm not sure if it is anything to worry about or not... I was checking the size on the bolt holes, and found that both 5/16" and M8 bolts were a loose fit in the holes, but 3/8" and M10 definitely would not fit... The wheels weren't countersunk to fit a conical lugnut / bolt the way most car wheels are either. I am wondering if I'd get slop in the wheel centering if I just used straight bolts?

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woodygb wrote:Centering is usually achieved by using the large hole in the middle of the wheel hub....thus the slop in the RETAINING bolts doesn't matter.
Key way, Key and Key Steel - if the key is fitted correctly there should be zero slop, the hub tightens around the output shaft.

Excellent links, unfortunate that adding to basket, then going through the process of ordering' then finding they don't deliver to outside the US' is disappointing. It's a shame Amazon or some smart shipping company doesn't have facilities to allow buying in the US, ship it to say Amazon facility, then they forward it to the UK for a fee. Maybe something does exist like that already?

It would be simpler to use a cutting disc on an angle grinder, then drill through the hub, and thread the hole drilled, then using the drill open up the freshly threaded hole on one side. So when you fit a socket head bolt, it pulls the hub tighter against the output shaft of the differential gear box. That over complicates for most. So if you want to reduce the slop, make a new key that fits in the output shaft and fits in the wheel. Stepped key. But they easiest solution is to drill through the hub opposite the key way thread it to 6mm x 1.25mm (coarse thread) or 6mm x 0.75mm (fine thread) - fine thread is more secure. Then use a 6mm dog nosed grub screw to secure. DO NOT use a product to glue the screw in place. Then punch a hole with a 6mm/6.5mm hole punch through a mouse mat. Use the cut out piece and stuff it in the hole behind the grub screw. It won't stop moisture getting in, and it may rust a bit. But it will keep the debris out of the top of the grub screw.
hub.jpg
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Re: New Tyres on my Puma 40

Postby woodygb » 17 Jan 2019, 11:24

You could ask if any of our U.S. members would be so kind as to purchase and ship them to you.
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Re: New Tyres on my Puma 40

Postby Mechniki » 17 Jan 2019, 11:28

I did find another site that sold the same product, again in the US and they would ship the pair, they were cheaper as sold as a pair at $38 but wanted $275 to deliver. AND that would definitely sting me at UK customs (they wouldn't know it was for a disabled person)
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Re: New Tyres on my Puma 40

Postby Mechniki » 17 Jan 2019, 11:31

woodygb wrote:You could ask if any of our U.S. members would be so kind as to purchase and ship them to you.

I could ship them to my younger brother (lives in Hollywood) then get them as prezzies at xmas
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Re: New Tyres on my Puma 40

Postby LROBBINS » 17 Jan 2019, 11:32

There are numerous freight forwarding outfits in the U.S. that provide a U.S. address and then ship abroad. Try a web search to find them, but do check their terms and conditions (and user reviews). Before I found sources for some things in Italy I used a couple of these companies - somewhat expensive, but workable.
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Re: New Tyres on my Puma 40

Postby woodygb » 17 Jan 2019, 13:26

Mechniki wrote:
woodygb wrote:You could ask if any of our U.S. members would be so kind as to purchase and ship them to you.

I could ship them to my younger brother (lives in Hollywood) then get them as prezzies at xmas


Have your brother mark the customs declaration as Gift or $10 value.
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Re: New Tyres on my Puma 40

Postby Mechniki » 17 Jan 2019, 14:24

woodygb wrote:
Mechniki wrote:
woodygb wrote:You could ask if any of our U.S. members would be so kind as to purchase and ship them to you.

I could ship them to my younger brother (lives in Hollywood) then get them as prezzies at xmas


Have your brother mark the customs declaration as Gift or $10 value.

that's an idea, but I am not THAT dishonest - I may skip the occasion event with a fake migraine/ (normally as on that day I have zero energy) - but I draw lines at being actively dishonest.

I bought some Lithium Ion batteries a few days ago on ebay. When I won the bid at £6.10, I paid via PayPal, then realised that they were collection only. So contacted the seller asking if I could pay for postage. They implied they could not be sent. I told them they could keep the product and have a couple of coffee's or tea's on me, or give the money to charity if they wanted to. They refunded me anyway... So I went back to PayPal and Gifted them £6.10
It was MY mistake, not theirs - though had it been more than £20 , I would apologise accept the refund, and then gift them £5 for whatever they wanted. Coz I am cheap
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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 20 Jan 2019, 01:16

I have mentioned it before, but I am willing to do shipping from the US to those living in "furrin coontries" :P for whatever the postage is... I can easily do US Postal Service, and UPS, Fedex is only slightly harder (another mile drive to the shipping point...)

In terms of customs and such - I can't see any differences between a government and a criminal protection racket - or any reason to give any avoidable amount to either....

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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 20 Jan 2019, 03:13

I have confirmed w/ a couple of our other machine shop guys that it shouldn't be a big problem to make a couple of these with the stuff we have here at the Asylum, and that way I can make something that fits exactly...

I even already own a couple feet of 4.25" or 4.5" aluminum round so I have the material....

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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 01 Aug 2019, 03:13

It has taken me FAR longer than I would have liked, but I have finally finished a drawing of a wheel hub that I feel pretty certain will work, in both my favorite LibreCAD and after much effort to figure out how to use it, in GCAD3D...

I'm attaching a JPG of my LibreCAD drawing to see what people think - any bugs? Design problems?

l-cad-spacer-v2.jpg


All dimensions are metric.

Stock is 4.25" round 6061-T6 aluminum bar.

The shaft is actually 0.75" with a 3/16" key - the size in the drawing is taken from standards for keyway dimensions in shafts and pulleys... (Minor annoyance that the CAD programs don't allow use of inch and metric in the same drawing...)

My plan is to tap the 4 bolt holes to M-8, and run bolts through from the back w/ permanent Loc-tite to serve as studs to bolt the wheels on....

The cross-bolt will be an M-6 Allen, w/ flat and lock-washers. I am mildly debating whether to Helicoil the cross-bolt threads or not.... (I have acquired Helicoil sets for M3-M12)

Bolts will be Stainless....

The other dimensions are based on the Aluminum 'Shirley Wheels'

I will probably be machining these on our CNC Bridgeport.

One of the advantages of this design is that I should be able to easily modify it to fit axles of other sizes pretty easily....

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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 01 Aug 2019, 03:16

Hmmm.... For some reason the picture didn't post, trying again....

l-cad-spacer-v2.jpg
2-D drawing, top and side views
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Re: New Tyres on my Puma 40

Postby LROBBINS » 01 Aug 2019, 08:47

Are you sure you want to use a key in aluminum? The keyway tends to enlarge over time with motor reversals. The cross bolt may eliminate that problem, but might you consider using a taper lock or similar?
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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 01 Aug 2019, 12:44

The key is not my first choice, but I have not been able to find a suitable taperlock that would be able to be readily adapted to a hub for the wheel.... I am also not at all sure of our ability to make a taperlock on the equipment we have here at AA - it looks like a non-trivial machining task....

The split hub w/ clamp bolt seems like the next best option as long as I can get the clamp tight enough to lock the hub onto the shaft - ideally the fit should be tight enough that the key is just about optional....

WoodyGB was one of the folks that pointed me at a similar commercial product for go-kart racers earlier in this thread - the one he pointed at was the wrong size, I'm just remaking the concept in the right size...

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Re: New Tyres on my Puma 40

Postby Burgerman » 01 Aug 2019, 13:36

but I draw lines at being actively dishonest.

Oooh. I dont. Its hard enough being disabled without worrying about trivialities and taxation.
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Re: New Tyres on my Puma 40

Postby LROBBINS » 01 Aug 2019, 18:40

Perhaps one of these (or others from the same source) might be a useful alternative:
https://shop.hpceurope.com/pdf/gbPDFauto/RTL450%2Epdf
https://shop.hpceurope.com/pdf/gbPDFauto/RT70%2Epdf
https://shop.hpceurope.com/pdf/gbPDFauto/RT25%2Epdf
They don't require tapered bores, but work like taper lock (and are easier to undo as your remove the screws and then turn them into "pusher" holes.

I don't know who the actual manufacturer is, or if there's a distributor in the U.S., but you might be able to find out.
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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 03 Aug 2019, 06:05

Interesting - easy enough to machine the part - easier than current as no need for the split, cross-bolt or keyway. That gets rid of a LOT of operations, some of which would be rather tricky to set up, especially the cross-bolt

They look rather "industrial" and would show unless I did some sort of extra effort to make a cover, but that isn't all that bad of a thing...

There seem to be several different manufacturers - I found at least a half dozen that are making similar looking products, Duck Duck for "Self Centering Locking Assembly". At first glance, at least some have sizes that are a closer match to the ~24mm thickness of the hub (I wouldn't mind reducing it to 16mm, but not sure that would be a good idea...)

Any idea what the torque output of our typical motors are - my project chair is supposed to be 6mph geared, 4-brush motors...

Most appear to be steel, which isn't great from a rust / looking nice standpoint, but that isnt a big issue...

A possible concern is that the motor shaft is 3/4" - and most of the companies seem to be only listing metric sizes, 19mm is close to 3/4" but not sure it is close enough - but there is also at least one company w/ inch series so that might not be a concern...

Thanks for pointing me at this style of lock....

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Re: New Tyres on my Puma 40

Postby Irving » 03 Aug 2019, 07:06

Those are really interesting Lenny, I'll knock up some drawings later today.

@goose - the likely max torque from a wheelchair motor is around 60Nm at stall - even the smallest will work. A more concerning number is the PN value which is the outward force on the hub, we need to be sure the hub isn't overstressed around the stud/bolt holes. I'll run some numbers later on both steel and ally hubs on both the RT25 and RT70 for 19mm shaft. Looking at the design of the sliding taper I reckon there is a direct relationship between the torque of the locking bolt and the inward and outward forces so it may be 'tuneable'.

What is the PCD of the rims you are planning? Are they the BM monkeybike ones?

Edit: just did a search, there are plenty of Stainless Steel versions :D
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Re: New Tyres on my Puma 40

Postby Irving » 03 Aug 2019, 07:30

This thread has got a little off track to the OP, maybe we should start a new one?
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Re: New Tyres on my Puma 40

Postby ex-Gooserider » 03 Aug 2019, 23:37

Irving wrote:Those are really interesting Lenny, I'll knock up some drawings later today.

@goose - the likely max torque from a wheelchair motor is around 60Nm at stall - even the smallest will work. A more concerning number is the PN value which is the outward force on the hub, we need to be sure the hub isn't overstressed around the stud/bolt holes. I'll run some numbers later on both steel and ally hubs on both the RT25 and RT70 for 19mm shaft. Looking at the design of the sliding taper I reckon there is a direct relationship between the torque of the locking bolt and the inward and outward forces so it may be 'tuneable'.


Thanks for the 60Nm figure, it makes me feel less worried about how much stress I'd be putting on these...

I would be somewhat surprised if the PN value was much of an issue... The 'spigot' section is 75mm OD, and the couplings from different brands seem to be about 47-50mm, so that gives about 12mm ~1/2" worth of 'meat' around the outside - even in aluminum that seems pretty stout...

I can't play with the diameters of the spigot or bolt circle as they are set by the wheel. I could turn the OD of the bolt face down, but it seems that would not be good... I could probably also cut out 'lobes' to get rid of some of the material between the bolt holes, but I'd want a good reason as it would potentially make the work holding harder and the machining mildly more complex.... I CAN play some with the thickness of the spigot or bolt surfaces.

Does it make any difference if the width of the hub is more or less than the width (length) of the coupling?

Even though 3/4" is not quite = 19mm (0.75" = 19.05mm, 19mm = 0.74805" according to my digi-micrometer) should I assume that it is close enough to be able to use a metric fitting (I have seen some inch versions as well)

I probably won't end up using the same parts that Lenny pointed at, but my first glance suggests that all are similar in size, so I'd expect any forces to also be about the same...

What is the PCD of the rims you are planning? Are they the BM monkeybike ones?


They are the 3.50-8 version but the same cast alloy style as the BM wheels - I got them from Shirley, just like BM did....

They have a 75mm center hole, and a 92.5mm bolt circle The bolt surface is about 8mm thick. The outer face of the center flange is centered on the rim, so the contact surface is inset from it that much.

Edit: just did a search, there are plenty of Stainless Steel versions :D


Glad to hear it, as I'd rather do stainless or alloy so I don't have to worry about rust issues -

In reference to your question of starting a new thread - We probably could start a new thread but unless BM can split this one to move what we have already said to a new thread, it is probably easier to stay with this one - which is sort of on the topic of doing different wheels / tires, and isn't seeing much other activity...

ex-Gooserider
T-5, ASIA-B
Jazzy 1100
Jazzy Select 6
Quickie Q-7
Invacare Mariner
Want to make / get a better chair, ideally one that stands.
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