Idler shaft extremely hot

[JPG]

Actually I had not(YET) read the post on your 'belts' thread.

I am not surprised that the belt jamming occurred(see my comments on the belts thread).

I have found that opening the motor pulley fully makes belt installation much easier.(pull it open manually)

[Majones1]

Actually I had not(YET) read the post on your 'belts' thread.

I am not surprised that the belt jamming occurred(see my comments on the belts thread).

I have found that opening the motor pulley fully makes belt installation much easier.(pull it open manually)

I saw Jacob Anderson do that in his video about changing that belt, and it looked pretty easy to do, but when I tried I could not get the sheave to budge.

[JPG]

Actually I had not(YET) read the post on your 'belts' thread.

I am not surprised that the belt jamming occurred(see my comments on the belts thread).

I have found that opening the motor pulley fully makes belt installation much easier.(pull it open manually)

I saw Jacob Anderson do that in his video about changing that belt, and it looked pretty easy to do, but when I tried I could not get the sheave to budge.

Pull harder Takes both hands. One can hold it.(or wedge)

You ARE installing it with the speed set to FAST?

[Majones1]

After retensioning the gilmer belt, I ran my Mk5 for 17 minutes, documenting the speed of each letter up to T, which took 12 minutes, then dropped back down to R for another 2 minutes before slowly decreasing speed to SLOW. The headstock got very warm, not hot, and was warmer down around the motor. The drive shaft hub was very warm, but not hot. The idler shaft hub was very hot, but I could still hold it, barely.

The Mk5 is running cooler now, so the gilmer belt adjustment helped. With the new 4L260 belt from ShopSmith, here are the speeds I recorded:

796 SLOW
872 A
985 B
1104 C
1237 D
1350 E
1480 F
1632 G
1788 H
1930 I
2112 J - Rush!
2285 K
2485 L
2670 M
2922 N
3142 O
3405 P
3647 Q
3950 R
4225 S
4500 T

My slow speed is slower than before I made these changes, it wasn’t going much below 1,000 RPM.

[Majones1]

Pull harder Takes both hands. One can hold it.(or wedge)

You ARE installing it with the speed set to FAST?

Thanks! I’ll try again next time I need to pull it apart, which hopefully won’t be too soon. Part of my problem was that I was doing it on my bench and couldn’t get enough leverage without pulling the headstock onto the floor, which I was trying to avoid. Jacob made it look like it was really easy. But, yes, I did go to fast speed when I was changing the belt, and when doing anything with the idler shaft or speed control.

[JPG]

After retensioning the gilmer belt, I ran my Mk5 for 17 minutes, documenting the speed of each letter up to T, which took 12 minutes, then dropped back down to R for another 2 minutes before slowly decreasing speed to SLOW. The headstock got very warm, not hot, and was warmer down around the motor. The drive shaft hub was very warm, but not hot. The idler shaft hub was very hot, but I could still hold it, barely.

The Mk5 is running cooler now, so the gilmer belt adjustment helped. Here are the speeds I recorded:

796 SLOW
872 A
985 B
1104 C
1237 D
1350 E
1480 F
1632 G
1788 H
1930 I
2112 J - Rush!
2285 K
2485 L
2670 M
2922 N
3142 O
3405 P
3647 Q
3950 R
4225 S
4500 T

My slow speed is slower than before I made these changes, it wasn’t going much below 1,000 RPM.

Thank You for posting this. Correct me if I am wrong, but these readings were taken with that 4L260 motor belt.(Narrow and Short)

The effects I believe would be as follows (Ya making me rethink all this).

EDIT: I may have to reconsider that which follows again.

With the speed control set at "FAST" :

The belt (narrow) would be positioned closer to the axle on the control sheave. The belt(short) would also be positioned closer to the motor shaft.(not as far out on the motor pulley) The effective take up of belt length is small on the idler pulley(due to smaller radius) compared the the motor pulley, but the shortness of the belt becomes the overriding difference, so the quill speed is slower than with a "correct" belt.

With the speed control set at "SLOW" :

The belt(narrow) would again be positioned closer to the axle on the control sheave(not as far out on the idler pulley). The effects are shifted to the opposite pulleys as above. Thus the larger pulley again becomes the dominant factor. In this case the result is faster speeds at slow.

I think that all adds up and agrees with the measurements.

Until just now I did not realize the effects are opposite at the speed control range limits.

[dusty]

The MarkV Sheaves Revisited.jpg (142.24 KiB) Viewed 857 times

A visual: The numbers are empirical as they represent my machine at a point in time. It is probable that the same data will not exist if collected elsewhere but they should be close.

[Majones1]

With the speed control set at "FAST" :

… but the shortness of the belt becomes the overriding difference, so the quill speed is slower than with a "correct" belt.

With the speed control set at "SLOW" :

… Thus the larger pulley again becomes the dominant factor. In this case the result is faster speeds at slow.

I think that all adds up and agrees with the measurements.

Until just now I did not realize the effects are opposite at the speed control range limits.

Since I’m new to the Mark 5 and don’t know the typical speeds others are seeing I don’t know what I should expect. A ShopSmith published speed chart shows that the SLOW speed setting should be 700 RPM, mine was 796, and all of my recorded speeds are 9-15% faster than what SS published (find the SS chart in a post at the link below). Because what I’m seeing are all higher than expected speeds, I don’t believe that what I’m seeing demonstrates what you described above.

I created a table showing my speeds as compared with the published speeds, then calculated the differences and percentage over published. See the table in the attached PDF below.

How much should I be concerned about the 200 to 400 RPM speed differences? I would guess that it will be important for me to stay aware of the true speeds of my Mk5.

ShopSmith’s Speed Chart:
viewtopic.php?f=10&t=23205&p=266209&hil ... rt#p266209

.

[JPG]

With the speed control set at "FAST" :

… but the shortness of the belt becomes the overriding difference, so the quill speed is slower than with a "correct" belt.

With the speed control set at "SLOW" :

… Thus the larger pulley again becomes the dominant factor. In this case the result is faster speeds at slow.

I think that all adds up and agrees with the measurements.

Until just now I did not realize the effects are opposite at the speed control range limits.

Since I’m new to the Mark 5 and don’t know the typical speeds others are seeing I don’t know what I should expect. A ShopSmith published speed chart shows that the SLOW speed setting should be 700 RPM, mine was 796, and all of my recorded speeds are 9-15% faster than what SS published (find the SS chart in a post at the link below). Because what I’m seeing are all higher than expected speeds, I don’t believe that what I’m seeing demonstrates what you described above.

I created a table showing my speeds as compared with the published speeds, then calculated the differences and percentage over published. See the table in the attached PDF below.

How much should I be concerned about the 200 to 400 RPM speed differences? I would guess that it will be important for me to stay aware of the true speeds of my Mk5.

ShopSmith’s Speed Chart:
viewtopic.php?f=10&t=23205&p=266209&hil ... rt#p266209

.

My description only referred to "slow" and "fast" speeds. nominal is 700 at slow and 5200 at fast.

You measured 796 and ????. What does yours measure at FAST. I misread the 4500 as "fast" not T.

[DLB]

Since I’m new to the Mark 5 and don’t know the typical speeds others are seeing I don’t know what I should expect. A ShopSmith published speed chart shows that the SLOW speed setting should be 700 RPM, mine was 796, and all of my recorded speeds are 9-15% faster than what SS published (find the SS chart in a post at the link below). Because what I’m seeing are all higher than expected speeds, I don’t believe that what I’m seeing demonstrates what you described above.

I created a table showing my speeds as compared with the published speeds, then calculated the differences and percentage over published. See the table in the attached PDF below.

How much should I be concerned about the 200 to 400 RPM speed differences? I would guess that it will be important for me to stay aware of the true speeds of my Mk5.

ShopSmith’s Speed Chart:
viewtopic.php?f=10&t=23205&p=266209&hil ... rt#p266209

.

You can, in theory, correct most of your error by performing a High Speed Adjustment. I say 'in theory' because I'm not comfortable recommending that with a shorter/narrower belt. But you obviously have a tach... The Adjustment does two things: sets the hard stop for maximum speed (long set screw in the speed control) and adjusts the speed indicator dial to be 'correct.' Basically you set the speed fast, determined by where the proper belt is riding in the motor sheaves. At that point, you set the hard stop as a limit and set the indicator dial to FAST. The only concern would be that the 4L260 could be riding too deep in the idler sheaves.

What you can easily do is set the machine to an intermediate speed, say 3500 RPM on the tach, remove the speed control handle, and set the indicator dial to "R." Removing the control handle disengages the speed indication from the speed control. So the only thing you'd be missing is the hard stop at FAST. I estimate right now you are about 'P + 1/3' at 3500 RPM. This will give you lower speed at every letter. I'm not sure that it will give you an actual lower speed.

- David