I happened to bump into the fan on our GM 4108 today while inspecting for leaks and noticed that there is a slight amount of rotational free play in the fan - maybe 1/16" or so.
Guys with the earlier GM buses have to be careful about their hubs breaking down, so my initial reaction was to worry. (Of course, that's my default setting anyway.) Then I looked at the manual and parts book to see how the thing is put together. Didn't help much, but for sure the hub itself is not the problem.
Looks like the mechanical drive runs at 1.0 to 1.59, which tells me that there is some type of gear reduction going on inside the drive between the crankshaft and fan. This is not a hydraulic drive - it's mechanical.
There is no side-to-side movement on the fan at all, so I do not think it's a bearing issue.
So, my question is how normal is this type of rotation free play in a mechanical drive setup like this? Just gear lash or is this something to actually be concerned about, like a loose mounting plate inside the drive?
Anyone happen to have photos of a mechanical drive like this opened up?
Don't look for a problem,,,,,,it will find you soon enough.!>>>Dan
They have backlash in the gears .about the only thing that goes bad is the rubber spacer and when it starts to fail you will know it,does your manual show a direct drive or a clutch pack drive ?
Definitely a mechanical direct drive with a 1:1.59 ratio on the gears.
Manual shows a PTO option, which we don't have. A/C runs from a belt off the main pulley.
[quote autho\,the r=richard5933 link=topic=35011.msg402827#msg402827 date=1600021721]
Definitely a mechanical direct drive with a 1:1.59 ratio on the gears.
Manual shows a PTO option, which we don't have. A/C runs from a belt off the main pulley.
[/quote]
That drive wouldn't be a problem the clutch pack drives can be a bitch
Richard,
I have the exact same fan hub/drive, as you do in my 1970 4108 Buffalo with the 318 Detroit.
Last September, we pulled the housing off and ran the seal out to install a new one
(as it was leaking) and I got to see the inside...unfortunately, I have not been able to find the pictures I had of that, as we put it all back together.
I have the same "rubber block" as I will call it and THAT is the point of concern I was told to keep an eye on for wear, as the rubber dries out and cracks, it CAN let go and the fan will eat that $3-4000 radiator for lunch !
Now you have me wondering about the slop (free play) in the gearing...I do not think we saw any at the time we had this all back together.
If you want to expand on this conversation, I would rather do by phone if you can find a way to PM me...I am afraid I do not have the computer intelligence to figure out how to suggest you do that though. John
Quote from: HoBoJo Busman on September 13, 2020, 12:51:26 PM
Richard,
I have the exact same fan hub/drive, as you do in my 1970 4108 Buffalo with the 318 Detroit.
Last September, we pulled the housing off and ran the seal out to install a new one
(as it was leaking) and I got to see the inside...unfortunately, I have not been able to find the pictures I had of that, as we put it all back together.
I have the same "rubber block" as I will call it and THAT is the point of concern I was told to keep an eye on for wear, as the rubber dries out and cracks, it CAN let go and the fan will eat that $3-4000 radiator for lunch !
Now you have me wondering about the slop (free play) in the gearing...I do not think we saw any at the time we had this all back together.
If you want to expand on this conversation, I would rather do by phone if you can find a way to PM me...I am afraid I do not have the computer intelligence to figure out how to suggest you do that though. John
I sent a PM to you with my phone number. You should be able to get the PM through the link above which reads "My Messages"
Look forward to talking with you to learn more about this mysterious rubber block.
My spare coach has that same play in the fan. Not a concern to me.
Quote from: chessie4905 on September 13, 2020, 03:57:49 PM
My spare coach has that same play in the fan. Not a concern to me.
They are a square cut spline and only wear in 1 direction, very little wear will translate into back lash on the fan nothing to worry about,just keep a eye on the rubber isolator aka block or spacer those are not to be had even from Luke
Quote from: luvrbus on September 13, 2020, 04:44:09 PM
They are a square cut spline and only wear in 1 direction, very little wear will translate into back lash on the fan nothing to worry about,just keep a eye on the rubber isolator aka block or spacer those are not to be had even from Luke
Good to hear that the backlash is normal.
I'm confused about the rubber isolator? Where is this rubber isolator/block/spacer thing to be found?
I'm not seeing it in the parts book either, so perplexed.
The only place I can see something like this would be inside the hub of the fan itself where the fan connects to the next piece which connects to the hub. There is zero free play between the fan and the pulley, either rotationally or side-to-side, so if the rubber thing is in the fan's internal hub I'm probably go.
Richard,
Yes, Inside the hub...if you use a mirror, you can see somewhat.
If there is no wiggle when you give the blade a good shaking... you should be alright, for NOW. When it lets go,(I was told, can be any time)... even if it feels somewhat tight.
This is subjective I suppose. BTW, I do not see any PM to contact you.
What the heck am I to look at to find it ?
Seriously, I struggle with this computer business. I am of a different place I think.
John
The fan seems firmly mounted to the hub, so if that's the point of concern I suppose I'm good for now.
Funny thing is this is the first I've heard about a problem with the rubber on a fan being a problem on anything other than the earlier models like the 3751. Never heard of anyone with a Buffalo having their fan go ballistic (literally & figuratively.)
Would love to see photos of the end of the fan showing the rubber bit if anyone has one. (I'm a visual learner - what can I say?)
Ahhh, go ahead and rip it apart. We're all curious.
I pulled out the manuals. There are no rubber components there. There is a metal plate with damper springs though. If fan damper fails, it still won't come apart. He may be thinking about 4104 or 4106.
Checked with Luke today. He confirmed that the hub on these won't fail like the ones on the 3751, and that the free play is normal.
The ones I have seen have a isolator between the fan and the hub,I tried to order that isolator from Luke for Mikey engine swap
Well here you go folks.
This is what I consider to be a #2 out of 10...
1 being horrible & 10 being the better end.
I paid $250 for this last year and returned it when
I compared it to the one presently on the engine in my 4108 Buffalo.
The one on the bus presently, I would rate a #8 or 9
so I will keep it for a few more miles
You all decide and do let me know what you think will you?
Quote from: HoBoJo Busman on September 14, 2020, 09:03:32 PM
Well here you go folks.
This is what I consider to be a #2 out of 10...
1 being horrible & 10 being the better end.
I paid $250 for this last year and returned it when
I compared it to the one presently on the engine in my 4108 Buffalo.
The one on the bus presently, I would rate a #8 or 9
so I will keep it for a few more miles
You all decide and do let me know what you think will you?
yep that was missing on Mikeys engine and the Utahclaimjumber tried to have one made
Out near the end the illustration shows black area with slashes. Probably the rubber you have. They list two fan hubs. One for 4108 and one for 4905. May be for amount of blades on fan. They use 8 and 6. The breakdown on the fluid fan doesnt show any rubber. Fluid may handle any shock. Fortunately, my driving coach has a fluid fan with varatherm removed with full time fan.
If I understand how that's put together, the inner metal sleeve is connected to the mechanical drive's output shaft, and the outer metal sleeve connects to the flange where the fan mounts. The only thing holding the two sleeves together is that rubber layer in between.
Do I have this right?
Quote from: richard5933 on September 15, 2020, 06:54:48 AM
If I understand how that's put together, the inner metal sleeve is connected to the mechanical drive's output shaft, and the outer metal sleeve connects to the flange where the fan mounts. The only thing holding the two sleeves together is that rubber layer in between.
Do I have this right?
It is a bonded rubber inner holding the 2 pieces together that is also AKA as a PTO coupling
Richard,
If you have it right here...
All I wanna know is ...
Where oh where can I get us all new ones?!
Quote from: HoBoJo Busman on September 15, 2020, 07:59:32 AM
Richard,
If you have it right here...
All I wanna know is ...
Where oh where can I get us all new ones?!
Why do we need new ones?
Well I for one,
Enjoy having spare parts on hand and replacing parts that are ready to fail,
(not that this particular piece is just yet, on the verge of catostrophic failure)
instead of waiting till something has me on the side of the road.
It's just my weird way of enjoying peace of mind in my own little head.
Maybe thats why I'm broke. I'm spare parts broke.
get a bad one, seperate the two pieces. clean and glass bead blast. buy liquid polyurethane-rubber two part kit on Amazon. make a rigid setup to hold so inner piece
is perfectly centered. pour in liquid.
read questions and answers. also check reviews.
Quote from: chessie4905 on September 15, 2020, 08:40:30 AM
get a bad one, seperate the two pieces. clean and glass bead blast. buy liquid polyurethane-rubber two part kit on Amazon. make a rigid setup to hold so inner piece
is perfectly centered. pour in liquid.
read questions and answers. also check reviews.
I couldn't separate the 2 pieces with a 20,000 lb press some military 8v92 have a coupling similar
probably need to drill or burr out the rubber or burn it out under controlled heat so as not to hurt the metal. Put it in the wifes self cleaning oven.
ie; I couldn't separate the 2 pieces with a 20,000 lb press.
I am thinking then, that we will keep it as it is then. Thank you
All the years on the forums, haven't heard of one failing on a Buffalo. Wonder what percentage actually have mechanical fans.