3d printed hollowtech BB spacers OK ?

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brucelee
Posts: 180
Joined: 19 Feb 2009, 10:39am

3d printed hollowtech BB spacers OK ?

Postby brucelee » 28 May 2020, 10:12am

Hi, I want to widen the Q factor (is it called this or stance width?) of my ultegra chain set by adding spacers and it's easiest for me to just print out some spacers but I'm concerned that this will allow movement of the cup threads possibly knackering the BB shell. Do they need to be made of something less compressible ? Are there plastic spacers being sold be the manufacturers or are all the supplied ones metal ?
Cheers,
Bruce.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: 3d printed hollowtech BB spacers OK ?

Postby Brucey » 28 May 2020, 11:10am

what, so you are planning on reducing the engagement between the BB splines and the LH crank? Bad idea; they fail often at this point even with full engagement, so reducing it is hardly likely to improve matters.

If you really want a higher Q value I would suggest that you buy a different crankset.

If you want to risk it and space the cranks out with minimum fuss it might be easiest to use the spacer that comes with some shimano triple chainsets; this goes on the spindle and doesn't require that you disturb the cups.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

tatanab
Posts: 4091
Joined: 8 Feb 2007, 12:37pm

Re: 3d printed hollowtech BB spacers OK ?

Postby tatanab » 28 May 2020, 11:31am

brucelee wrote:Hi, I want to widen the Q factor (is it called this or stance width?) of my ultegra chain set by adding spacers and it's easiest for me to just print out some spacers but I'm concerned that this will allow movement of the cup threads possibly knackering the BB shell.
That would move chainrings outboard and change your chainline. If al you want is a wider stance for your feet then pedal extensions might be the way ahead. Various sizes available such as
https://www.sjscycles.co.uk/pedals-clea ... 916-195mm/

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fausto99
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Joined: 19 Sep 2011, 10:06am

Re: 3d printed hollowtech BB spacers OK ?

Postby fausto99 » 28 May 2020, 4:16pm

brucelee wrote:... Do they need to be made of something less compressible ? Are there plastic spacers being sold be the manufacturers or are all the supplied ones metal ?...

I wouldn't like to comment on BB use but I had an attempt at replacing a brake ferrule with a 3D printed one. It cracked to pieces when I first tried the brake (with the bike on a work stand). I'm sure that as well as choosing the right plastic, you have to use a filler when moulding parts to get the mechanical properties needed for any particular application. Can you 3D print with e.g. glass filled plastic?

brucelee
Posts: 180
Joined: 19 Feb 2009, 10:39am

Re: 3d printed hollowtech BB spacers OK ?

Postby brucelee » 28 May 2020, 4:19pm

Brucey wrote:If you really want a higher Q value I would suggest that you buy a different crankset.
cheers

Do you know of a crankset that will fit with the ultegra 52/36 rings ? It's R8000, 4 spoke design.

Brucey
Posts: 39497
Joined: 4 Jan 2012, 6:25pm

Re: 3d printed hollowtech BB spacers OK ?

Postby Brucey » 28 May 2020, 4:27pm

chainrings and cranks are very specific things these days. I doubt that you will easily find another crankset which will use the extant chainrings and the came chainline and a different Q.

Why do you want a different Q exactly? Do you want to keep a road chainline?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

brucelee
Posts: 180
Joined: 19 Feb 2009, 10:39am

Re: 3d printed hollowtech BB spacers OK ?

Postby brucelee » 28 May 2020, 4:29pm

tatanab wrote:That would move chainrings outboard and change your chainline. If al you want is a wider stance for your feet then pedal extensions might be the way ahead.
The chain line's out of whack anyway - the guys (or gals) at ribble don't seem to know about Pythagoras theorem. I've tried 20mm(per side) pedal axle extensions and they are too long. I'm currently using Ultegra +4mm SPD SL's but need a couple of extra mm on the right. I figure I could add 1.5mm to the pedal axle with washers and maybe a 1mm at the bottom bracket/frame interface. I already have a 2.5mm spacer between the BB and the crank. I could 3d print a longer one of these I suppose, just thought it might be more secure if the cup was moved out a bit instead.

brucelee
Posts: 180
Joined: 19 Feb 2009, 10:39am

Re: 3d printed hollowtech BB spacers OK ?

Postby brucelee » 28 May 2020, 4:35pm

fausto99 wrote: I'm sure that as well as choosing the right plastic, you have to use a filler when moulding parts to get the mechanical properties needed for any particular application. Can you 3D print with e.g. glass filled plastic?
What I'm worried about is the spacer compressing and the threads of the cups and frame being subjected to movement causing wear. That's why I was asking what material the manufacturers spacers are made of.

brucelee
Posts: 180
Joined: 19 Feb 2009, 10:39am

Re: 3d printed hollowtech BB spacers OK ?

Postby brucelee » 28 May 2020, 4:37pm

Brucey wrote:Why do you want a different Q exactly? Do you want to keep a road chainline?
cheers

My right knee is hanging out (I'm very wonky). Before I tried the various pedal extensions, I was experiencing knee pain.

Brucey
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Re: 3d printed hollowtech BB spacers OK ?

Postby Brucey » 28 May 2020, 4:45pm

speedplay pedals are available with different length spindles, and you can increase Q that way. It might be the easiest way of doing it?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

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Gattonero
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Location: London

Re: 3d printed hollowtech BB spacers OK ?

Postby Gattonero » 30 May 2020, 10:11am

If the BB has a BSA thread it couldn't be easier: use some 10sp cassette spacers, Sram ones are excellent because have a round ID.
More difficult is for an italian-threaded BB, you'll have a hard time finding a 35mm ID spacer.
But rather than messing with the chainset, altering the chainline and all that, just use some extensions for you pedals: cheaper, quicker, no fuss. What's not to like? £15 and sorted in seconds :)
https://www.sjscycles.co.uk/pedals-clea ... -916-inch/

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Brucey
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Re: 3d printed hollowtech BB spacers OK ?

Postby Brucey » 30 May 2020, 10:22am

OP has been using pedal extenders already...? I presume that he is after a more elegant solution?

BTW the idea that adding spacers at the BB would increase Q by a comparable amount to pedal spacers, without causing big problems, is a bit of a stretch.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

tatanab
Posts: 4091
Joined: 8 Feb 2007, 12:37pm

Re: 3d printed hollowtech BB spacers OK ?

Postby tatanab » 30 May 2020, 10:47am

Brucey wrote:BTW the idea that adding spacers at the BB would increase Q by a comparable amount to pedal spacers, without causing big problems, is a bit of a stretch.
Indeed. Q is influenced by the cranks and the bottom bracket overall length. Since neither is changing here the Q is constant, just everything is shifted to the right a bit. Or am I missing something, not having any modern chainsets with external gubbins?

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: 3d printed hollowtech BB spacers OK ?

Postby Brucey » 30 May 2020, 11:08am

you can slide the LH crank along the spline a little in a Hollowtech II setup (and thus increase Q a little), but this is at the expense of the integrity of the whole arrangement. 2-3mm is about the limit; pedal washers would be about as good.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

brucelee
Posts: 180
Joined: 19 Feb 2009, 10:39am

Re: 3d printed hollowtech BB spacers OK ?

Postby brucelee » 31 May 2020, 8:48am

I tried 20mm pedal extensions and they were too long. Worth noting that they gave a similar Q to a hollowtech triple which is what I used to ride. My knees moved inwards as pedal pressure increased. Starting to think the problem might be elsewhere. My left leg feels well planted and powerful whatever spacing I use, the right always weak. I printed out a cleat shim and will try it today, though it is only 1mm. Part of the original question still remains - Would it be OK to use a plastic spacer between the cups and the frame ? Also, would it be OK to use a plastic spacer as a pedal spacer ?