Author Topic: FD1 drive belt slipping off the flywheel  (Read 1076 times)

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Offline cwh

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FD1 drive belt slipping off the flywheel
« on: 11:18, 08 December 20 »
Hi everyone!

Due to some "special reasons"™ I have now quite some spare time to do things I wanted to do for ages. So I digged into my pile of old computers and tried the Amstrad/Schneider CPC 464 + DDI-1/FD-1 which I bought about 20 years ago.

The CPC works quite well - including the tape drive - so I started to fix the FD-1. Of course the belt was long gone, so I bought a new one and replaced it. Checking the manuals here and elsewhere in the Internet - it wasn't a big thing. (Not even a chance to lose the write protect pin since the drive is one of the ones having an optical sensor).

So the drive worked very well – at least for a while: After only a few minutes of read access the new belt just slipped of the flywheel. I put it back on - but after a minute: again.
So I wonder what is wrong here. The flywheel has no flange to hold the belt. I guess that is by design. Does that mean the alignment of the spindles is not ok? Did anyone else ever encounter this problem?

I was definitely not the first one who ever opened this drive. The previous owner apparently tried to replace the belt by a random rubber band. Using that he apparently had the same problem as I have now with the real belt. To hold it in place he pinched a piece of metal under the circuit board to hold the belt down on the flywheel. I of course removed this piece of metal - but maybe I need to reinstall it?

Any ideas?

Christopher

Offline Bryce

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Re: FD1 drive belt slipping off the flywheel
« Reply #1 on: 13:36, 08 December 20 »
If the belt keeps popping off, then there is still some crap from the old belt on the wheels. You'll have to remove every bit of gunk from the wheels for it to work properly.

Bryce.

Offline cwh

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Re: FD1 drive belt slipping off the flywheel
« Reply #2 on: 12:55, 09 December 20 »
Thanks for that hint – although I thought I got all the dirt I'll try cleaning even better.
Stay tuned - I'll report any progress.

Offline cwh

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Re: FD1 drive belt slipping off the flywheel
« Reply #3 on: 02:03, 13 December 20 »
Ok, nothing more to clean - definitely no gunk any more. But the problem remains.
Not sure if it is the right belt. What should be the right size? According to that page here it should be 71×0,6×2,8 ⇒ 223 mm circumfence.I measured the one I got from eBay, it is ~184 mm circumfence, means ~58,5×0,6×3
That means mine is just too small. Can you confirm that? Maybe I should note that my drive is a Matsushita EME-150A
Christopher
« Last Edit: 02:04, 13 December 20 by cwh »

Offline Audronic

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Re: FD1 drive belt slipping off the flywheel
« Reply #4 on: 02:30, 13 December 20 »
@cwh


I have made up a piece of wood with 2 nails spaced at 105 mm this is what I use to test the belt.


Keep Safe


Merry Christmas


Ray
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If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Offline GeoffB17

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Re: FD1 drive belt slipping off the flywheel
« Reply #5 on: 03:14, 13 December 20 »
Hmm, get all these different measurements?

A few years ago I got a pair of repl bands for my PCW, one is happily working still on my PCW, the other is here, still 'a spare'!   This one is 11cm long (where the loop is flattened against the ruler) meaning the circumfence (sp?) would be twice this i.e. 220mm.

My understanding is that the band should fit with the slightest stretch, so that the band is tight enough to grip.  Just.  Too tight will prob still work, but will not last very long.   Too slack will not grip enough and will cause various problems.

The two sizes just suggested here, one seems way too tight (184mm)   The other slightly too slack (223).  The 105mm length would give 210 circum which may be slightly too tight, but prob OK.

The band that keeps riding up might be OK for size, but might not be perfectly even.   I.e. if you rest the loop on a piece of white paper the edge of the loop should be flat to the paper all the way around, and the same for both sides.   Not sure if the band is too tight/slack how this would affect any problem due to imperfect loop.

Then again, when Bryce had my drive to repair the stepper motor he may have put a new band on anyway, even though the band that was there was just about new!!  So the band I have may NOT be the same size as the one that's working happily.

Geoff

Offline tjohnson

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Re: FD1 drive belt slipping off the flywheel
« Reply #6 on: 03:23, 13 December 20 »
71×0,6×2,8 is the correct size.

Offline Audronic

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Re: FD1 drive belt slipping off the flywheel
« Reply #7 on: 03:27, 13 December 20 »
Hi All


The Wooden tester was made after purchasing some belts from a known reliable seller.
Placed the belt on the block and put the 2 nails in with the belt lightly stretched.


Keep Safe


Merry Christmas


Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Offline xesrjb

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Re: FD1 drive belt slipping off the flywheel
« Reply #8 on: 09:11, 13 December 20 »
Ok, nothing more to clean - definitely no gunk any more. But the problem remains.
Not sure if it is the right belt. What should be the right size? According to that page here it should be 71×0,6×2,8 ⇒ 223 mm circumfence.I measured the one I got from eBay, it is ~184 mm circumfence, means ~58,5×0,6×3
That means mine is just too small. Can you confirm that? Maybe I should note that my drive is a Matsushita EME-150A
Christopher


You are right, the belt is to small. Have a look at german ebay...


xesrjb
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Offline Bryce

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Re: FD1 drive belt slipping off the flywheel
« Reply #9 on: 12:11, 13 December 20 »
If it's too small, it's definitely going to pop off. This is where I get my replacement belts: https://www.ebay.de/itm/Sinclair-Spectrum-3-Amstrad-Computers-Replacement-3-Disk-Drive-Belts-x5/260724655835

Bryce.

Offline cwh

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Re: FD1 drive belt slipping off the flywheel
« Reply #10 on: 14:24, 13 December 20 »
OK, thank you all for confirming my suspicion!I'll try to get a new belt from the UK seller Bryce suggested. Hope to get it before Bre*it.

Offline cwh

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Re: FD1 drive belt slipping off the flywheel
« Reply #11 on: 14:33, 23 December 20 »
Ok, problem solved!
I got a belt  71.0 × 0.6 × 2.8 mm and it works like a charm!
Got it from Thakker:And also got belts for the 464 tape drive:Thank you all for your help and have happy holidays!
Christopher