Belt mistery

[Sonic EscapeParticipant @sonicescape38234]

This is embarrassing but I don’t know how to reassemble my lathe! On the right it is the lathe before disassembling it. And on the left is when I put it back. I can’t understand why the belt is so much larger! That tensioning wheel can’t compensate for such a big increase in diameter. What am I doing wrong? It looks to me that I put back everything in the same way. And I have only one belt, no risk to mix them.

 

[JuddyParticipant @juddy]

I can’t see your the picture, but did you try google image for similar lathes to compare assembly

[Sonic EscapeParticipant @sonicescape38234]

The lathe is an Emcomat 7. I found this picture. The black metal part that supports the adjustable idler was mounted in reverse in my case. But this is not the problem. I mounted it like in the picture and the belt is still way to large.

 

 

 

[Phil PParticipant @philp]

That is a bit of a puzzle but here are my initial thoughts.

The position of the red pulley is not variable so forget that.
The position of the tensioner looks to be the same as the “before” photo so probably forget that as well.

That only leaves the motor, I would double check the mountings / adjustment for that as a starting point.
Have you maybe left some spacers out somewhere ?

Phil P

[Sonic EscapeParticipant @sonicescape38234]

The motor is mounted like this. Unfortunately the exploded view from the manual doesn’t help because it looks like I have a different version of the mounting method. But still I can’t imagine what could be wrong. There are 4 M5 screws coming out from the bed and the motor has two black bars that connect to the screws. I don’t see how to mount the motor in a lower position.

[peak4Participant @peak4]

It’s really hard to tell from the photos, and I don’t know how the motor is built, or what type it is.
Are the mounting brackets offset from the centre line of the motor?

If so, is it possible that when disassembling and refurbishing the motor, that you have reversed the end castings?
I don’t even know if that’s possible, but effectively, the spindle would be sicking out from the wrong end, necessitating mounting the motor upside down compared to when it was previously fitted.
That is, the armature has been re-fitted reversed left to right along its axis compared to previous.

Bill

[blowlampParticipant @blowlamp]

The motor mounting looks a bit odd because of the gap between the bars and the bed, which means that the bolts don’t have the correct clamping effect. Are you sure that spacers or bracket of some sort aren’t supposed to fit between the motor and the bed?

The correct size of belt is fitted, isn’t it?

Martin.

[Mike HurleyParticipant @mikehurley60381]

I agree with Martin.

In your original pair of pictures, if you draw an imaginary line between the two axis of the main pulley and motor, in the ‘original’ one that line would ‘touch’ the edge of the adjustment pulley. In the later one there would be a gap . Only the position of the motor can affect that. Recheck the. Mounting.

Note : the 2 photos appear to have been taken from roughly the same angle, so I’m assuming there’s no visual distortion.

Mike

[JasonBModerator @jasonb]

Is that the same pulley on the motor?

The painted up lathe looks to have a pully with a flange and the toothed area looks a smaller diameter than the original unflanged pulley.

[peak4]

On peak4 Said:

It’s really hard to tell from the photos, and I don’t know how the motor is built, or what type it is.
Are the mounting brackets offset from the centre line of the motor?

If so, is it possible that when disassembling and refurbishing the motor, that you have reversed the end castings?
I don’t even know if that’s possible, but effectively, the spindle would be sicking out from the wrong end, necessitating mounting the motor upside down compared to when it was previously fitted.
That is, the armature has been re-fitted reversed left to right along its axis compared to previous.

Bill

I understand what you mean but the mounting brackets seems to be symmetrical. So reversing the motor end castings should cause no effect.

On blowlamp Said:

The motor mounting looks a bit odd because of the gap between the bars and the bed, which means that the bolts don’t have the correct clamping effect. Are you sure that spacers or bracket of some sort aren’t supposed to fit between the motor and the bed?

The correct size of belt is fitted, isn’t it?

Martin.

Here you can see better why there is that gap. I don’t think there was a spacer there because the screws would be too short. I added some soft material between the bed and the motor in a hope to reduce the noise. And anyway moving the motor a few cm horizontally would not tension the belt. It is a pity that I don’t have the manual for this version of mounting.

 

On Mike Hurley Said:

I agree with Martin.

In your original pair of pictures, if you draw an imaginary line between the two axis of the main pulley and motor, in the ‘original’ one that line would ‘touch’ the edge of the adjustment pulley. In the later one there would be a gap . Only the position of the motor can affect that. Recheck the. Mounting.

Note : the 2 photos appear to have been taken from roughly the same angle, so I’m assuming there’s no visual distortion.

Mike

You mean like this? In the left picture the motor is mounted a little to the left. Because of the soft material I added between the motor and the bed. Horizontal position shouldn’t matter much, but I’ll remove that material just to check. Anyway I don’t have other ideas.

 

 

[JasonB]

On JasonB Said:

Is that the same pulley on the motor?

The painted up lathe looks to have a pully with a flange and the toothed area looks a smaller diameter than the original unflanged pulley.

Yes, is the same pully. I don’t have a similar one. The pully doesn’t have a flange. It is a washer that normally was on the other end, between the pully and the motor. But I forgot to mount it. And the pully is stuck so I added the washer on the opposite position.

[Sonic EscapeParticipant @sonicescape38234]

Here you can see how much I have to lower the motor in order to tension the belt! Something is seriously wrong in the way I reassembled this part of the lathe.

[JasonBModerator @jasonb]

Swing the tensioner right up, it needs the roller a lot closer to the spindle pulley

[Mike HurleyParticipant @mikehurley60381]

Out of interest – With the motor mounted normally, remove the 2 screws holding the adjuster mount plate. Manually push the assembly across to the left against the belt-  how far could you push it?

This problem has got to be something stupid simple?

[[email protected]Participant @tminusayahoo-co-uk]

 

Also, is it possible you have dismantled the tensioner pulley and reassembled it on the reverse side?   (just a thought)

[Nigel Graham 2Participant @nigelgraham2]

I don’t think the fault is that damping pad. Looking at the geometry of it all, if anything the pad would tend to tighten the belt, but its effect is probably minimal anyway.

[peak4Participant @peak4]

Yes, the two mounting points for the motor do look symmetrical, so it seems to rule out that one.
The exploded diagram of the other motor (Page 13 of the manual) shows the same part number for each end, so it would be possible to reverse the castings, but it looks like it wouldn’t make any difference.
Similarly the two long bars with flats on would move the motor even closer to the headstock if reversed.
Not wishing to talk down to you, but are there any bits left over? I’m thinking 4 tubes to space the motor out slightly between the round (flattened) bars and the headstock.

Alternatively, I see you now have the tensioner idle pulley in the same orientation as the one in the photo off Tony’s site; wasn’t it the other way round previously? This photo appears to show the belt length; does that tally?

How is the journal (2) mounted to the plate (1)? Did you take it off when cleaning and refix on the opposite side?
If it can be fixed the opposite side, maybe reverse the plate so that the curved slot is on the side further from the headstock; That would also move it upwards and allow more wrap around the top pulley.

Page 33 of the manual

I wonder if the tensioner might be a multi use part, assembled different ways around, and fixed in opposite directions depending on which motor is fitted.

Bill

[peak4Participant @peak4]

One thing that isn’t obvious, from your posts on this thread, is that both the photos in the opening post above are of the same lathe, before and after stripping/reassembly, which might mislead some people (me included).
From your other thread; https://www.model-engineer.co.uk/forums/topic/a-new-lathe/

The tensioner is the other way around, but seems to be working OK.

Do you have any other original photos of your lathe from a bit further round to the left?

[peak4Participant @peak4]

Final one for now; a completely offbeat thought.
The manual I linked to earlier seems a little confusing, as some of it shows a prismatic bed with associated groove under the headstock on pages 5/7. (The manual is labelled as Emcomat E7 & V8 with different part numbers)
Page 3 shows a flat topped bed.
Your lathe is flat topped and has a spacer under the headstock, painted red after your restoration.
Is it fully symmetrical, and does the headstock bore line up with the tailstock?
Could the headstock be set too far to the rear, changing the distance between the motor spindle and headstock input pulley?

Bill

[Grindstone CowboyParticipant @grindstonecowboy]

Correct me if I’m wrong, but it looks to me that, if the tensioner is up as far as it would go towards the spindle, then moving the motor closer to the casting would tighten the belt?

Obviously, you’d do that the other way round when actually adjusting it – motor first, then tensioner.

Rob

[peak4]

On peak4 Said:

Your lathe is flat topped and has a spacer under the headstock

That was going to be my very unlikely question: if the headstock has been removed from the bed for the porch painjob (sic), has it been re-mounted correctly? If the motor won’t go down, does the headstock need to go up?

Someone with the appropriate photo analysis skills could scale (overlay?) the two photos and see if the measurement between motor and input pulley is the same. Spindle to input pulley clearly cannot change.

[Speedy Builder5Participant @speedybuilder5]

Is the tensioner pulley on the correct side of the adjusting plate ?

[JasonB]

On JasonB Said:

Swing the tensioner right up, it needs the roller a lot closer to the spindle pulley

Doesn’t help, the belt is too large.

On Mike Hurley Said:

Out of interest – With the motor mounted normally, remove the 2 screws holding the adjuster mount plate. Manually push the assembly across to the left against the belt-  how far could you push it?

This problem has got to be something stupid simple?

Quite far. This can’t be the solution. I agree that the problem has a very simple cause

On peak4 Said:

Alternatively, I see you now have the tensioner idle pulley in the same orientation as the one in the photo off Tony’s site; wasn’t it the other way round previously? This photo appears to show the belt length; does that tally?

Yes. it was the other way round. But in both cases the tensioner can’t compensate for the extra belt legth.

On peak4 Said:

How is the journal (2) mounted to the plate (1)? Did you take it off when cleaning and refix on the opposite side?
If it can be fixed the opposite side, maybe reverse the plate so that the curved slot is on the side further from the headstock; That would also move it upwards and allow more wrap around the top pulley.

Page 33 of the manual

I wonder if the tensioner might be a multi use part, assembled different ways around, and fixed in opposite directions depending on which motor is fitted.

Bill

I didn’t touched the tensioner assembly. Also the journal can’t be removed. It has some sort of press fit mount.

On peak4 Said:

Final one for now; a completely offbeat thought.
The manual I linked to earlier seems a little confusing, as some of it shows a prismatic bed with associated groove under the headstock on pages 5/7. (The manual is labelled as Emcomat E7 & V8 with different part numbers)
Page 3 shows a flat topped bed.
Your lathe is flat topped and has a spacer under the headstock, painted red after your restoration.
Is it fully symmetrical, and does the headstock bore line up with the tailstock?
Could the headstock be set too far to the rear, changing the distance between the motor spindle and headstock input pulley?

Bill

The spacer under the headstock can’t influence this. There headstock position relative to the bed is fixed by 6 screws. I can’t move it horrizontaly in any direction more than a few mm.

On Grindstone Cowboy Said:

Correct me if I’m wrong, but it looks to me that, if the tensioner is up as far as it would go towards the spindle, then moving the motor closer to the casting would tighten the belt?

Obviously, you’d do that the other way round when actually adjusting it – motor first, then tensioner.

Rob

Yes, that is true. But still is not enough. there is no combination where the tensioner can tension the belt.

On DC31k Said:

On peak4 Said:

Your lathe is flat topped and has a spacer under the headstock

That was going to be my very unlikely question: if the headstock has been removed from the bed for the porch painjob (sic), has it been re-mounted correctly? If the motor won’t go down, does the headstock need to go up?

Someone with the appropriate photo analysis skills could scale (overlay?) the two photos and see if the measurement between motor and input pulley is the same. Spindle to input pulley clearly cannot change.

Hey, what’s wrong with my panting? I like it 🙂

I regret that I didn’t made more picture before disassembling the lathe. But even with the one I have I’m confident that I reassembled this parts like before. The headstock is fixed to the bed with 6 screws. So there is only one way to mount it. At it’s height is given by the red riser block.

Anyway, I’m thinking to declare it an unresolved mystery and order another belt. Are these types made in small diameter increments?

[Grindstone CowboyParticipant @grindstonecowboy]

A further thought – can those rods that the motor mounts on rotate? If the lower one was closer to the casting than the top one, the centreline of the motor would be lower, tightening the belt?

Rob

[Phil PParticipant @philp]

Why not try and have the tensioner roller on the other side of the belt pulling it forwards. I mean the tensioner on the outside of the rearmost part of the belt.
That might take up a bit more slack and get you running.

But I can’t help thinking you need to order a shorter belt in the longer term.

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