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Pillow block questions

Jake 555

Plastic
Joined
Feb 23, 2023
Hi,
Saw a question on this forum from 2016 and there seemed to be some very knowledgeable answers, but not the answer I needed.

So pillow blocks tolerate misalignment, have spherical outer bearing surfaces and so tolerate the shaft coming through the block at various angles.

Problem is, same as the other guy, I don't have the space on my short shaft for two pillow blocks.

So I need something, that looks LIKE a pillow block but does not allow this tilting of the shaft.

Might be easier if I say what I'm trying to achieve.
I wish to use a bicycle quick release rear hub, machined down to take its flanges down to 2 inches. Then filled between the flanges to create a parallel sided cylinder- my shaft.


I then need said shaft to rotate - but that is all. It is to change a mid drive electric mountain bike into a power take off device. So the back wheel is removed, then the bike is clipped into the PTO quick release hub -my shaft.

Problem is my shaft will be 50 mm long, and a single 2 inch pillow block is 50 mm wide. So only space for one.

I don't want to share dropouts, so use the existing hubs bearings, so a set of dropouts just wider than mine, because I want the bike's rear suspension to continue to work ( the whole thing is going into a boat, so suspension is handy). If you're making an amphibious ebike powered boat, you might as well have suspension too if the bikes already got it.

I'm not a mechanical engineer in any sense ( more of a boatbuilder)
So unsure of terminology. Maybe there are alternative bearings that are much narrower so I can mount a pair opposite each other on the insides of opposing plates all within my 50 mm shaft?

I want a system that means the rear dropouts of the bike drop straight into my hub, but obviously out of the saddle pedalling/ sprinting would be good too and this requires a hefty bearing that will resist the shaft being tilted. A pillow block designed to allow misalignment obviously would be the wrong choice. But I like it that pillow blocks come in stainless and thermoplastic, plus I can see how the tubular inner with its twin grub screws would sleeve onto my shaft and not shift side to side once the grub screws are tightened. My shaft will be carbon/ epoxy because that is a material I can work with.

I lack the skills to make a split aluminium unit clamped either side of the hub then turned down to a fair shaft, but roll wrapping a load of carbon round the hub oversized then turning it down to size with a sanding block- that I Can do! I can even use my ebike as the lathe!

This aspect appeals to my simple boatbuilders mind and pillow blocks are quite cheap, but what do I actually need?
 

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why can't you use the bike axle?
Because there is not enough clearance to get anything in between the bikes frame and the gear cassette on the drive side, plus clamping the hub to fixed dropouts in the boat as well as the bikes dropouts would stop the rear suspension working.
 
FWIW not all pillow blocks have self aligning bearings.
Difficult to see which ones do and don't online. Any tips for differentiation?
Is there specific terminology for those that don't self align, or is it just ' non self aligning '? Buying the wrong thing could become costly.
 
Because there is not enough clearance to get anything in between the bikes frame and the gear cassette on the drive side, plus clamping the hub to fixed dropouts in the boat as well as the bikes dropouts would stop the rear suspension working.
I still don't understand why you need some kind of self aligning bearing? Sacrifice one gear on the cluster and use chain drive to another shaft where the power will be delivered to it's target. Chains are inherently self-aligning, this is how derailleurs work.
 
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I *think* rigid pillow blocks are “bearing housing”. Not sure, I looked for a short time and only found plain bearing varies.
How rigid is rigid?
Guessing axle, now spinning vs fixed bike axle with spinning hub- what is diameter of axle?
If not so rigid, Igus bushings with flanges on both sides of a hole drill in a flat bar?
 
I'm doing some research on different hubs, some older ones are smaller diameter. I might be able to bolt two cheap aluminium two bolt self aligning flange bearings back to back, then sandwich them between two vertical plates with holes in them.
These flange bearings seem to go up to 35 mm shaft size. I would just need to find a hub that will machine down to 35 mm. Might have to trial and error destroy a few hubs until I find one that will machine down.
 
Well I looked a bit and have yet to find any pillow blocks that are not self-aligning. Not sure of the correct terminolgy for the rigid style. I guess the only rigid blocks I've ever seen were coincidentally ones I used to make a set of bicycle rollers as a teenager. Got them from grainger. They had a cast aluminum housing and the bearings were staked in and likely wouldn't stand up to your application.

So this bearing has a 2" bore? That's a good sized bearing and any pillow block you find will be pricey and hugeous. And a lot of rolling resistance.

Maybe you will be better served by a custom made housing with two shielded narrow cross section bearings. Be prepared to pay.
 
this whole post is about as clear as mud...
sounds like you want a quick release bearing to slide in and out of something?

machine parts and make them fit. modify shafts etc.
chains need not to be perfectly aligned, just close.

if you need a bike frame, you can seperate the 2. have a seperate rod that holds the bike, and have a longer chain to a seperate hub behind that.
 
I still don't understand why you need some kind of self aligning bearing? Sacrifice one gear on the cluster and use chain drive to another shaft where the power will be delivered to it's target. Chains are inherently self-aligning, this is how derailleurs work.
I am sacrificing about 3 gears on the cluster. It's a relatively powerful ebike, so I rebuild the clusters and have a wider spacing of 5 gears in the outer positions. The 1500w motor has the torque to not need as many gears as usual, and keeping the chain down in the outside of the cluster keeps a straighter chain line, roughly doubling chain life. (Ebikes EAT bicycle chains!). The three spare cogs take up the spacing on the inside of the cassette, and yes, one of these inner cogs will be taking the drive aft to a drive leg and into the water.

The hub system uses a Shimano cassette cluster, which cannot be shortened, or not without skills far beyond mine.

The bike, or any other bike I put on it has indexed gears. Ebikes are very intolerant of being between two gears- the indexing has to be set perfectly. So my rearranged Shimano 8 speed cassette hub on the bike, has to match in terms of span, indexing etc the matching rearranged Shimano 8 speed cassette in the boat.

Setting up a bike to drive the boat permanently, or semi permanently would be much easier. This is set to be adjustable, quickly and easily for a range of multiple bikes. And for the bike to be removed and ridden away in seconds.

Your other query about going outside the dropouts. This creates issues with my hope to have multi bike compatibility. Modern aluminium mountain bikes have a vast array of differently sculpted dropouts, especially bikes with rear suspension. They aren't flat steel plate dropouts any more that another flat plate would reliably clamp to. On the drive side there is about 2 mm between the bottom cog and the frame. If there was ANY more space, Shimano would have put another gear in there! This is dictated by the width of the cassette. I'm not getting into adapting cassette bodies when all I need is the correct bearing to support the hub in the middle.
There is also the complication of the derailleur on the drive side, which still needs to be able to function. Going outside the dropout means you enter a necessity to have some sort of (weakening) swan neck arrangement and different bikes rear derailleurs move in different arcs according to chain length.

I want this system to fit any bike with a 135 mm rear axle, not just my bike.
 
How about Plummer blocks? They are made for 'non self aligning bearings.' ********* and probably others made split roller bearings so you could fit them between fixed flanges. This is a Rolls Royce project!
 








 
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