Relining a forklift brake drum - is it possible? Concerns?

[Jonno_G]

Hi all, this is my first question here so if it's in the wrong place I'm sorry.

I'm in the (very slow) process of returning a 1950's Conveyancer forklift to serviceable condition. The first issue I need to address is the complete absence of functional brakes. After no small amount of work I have managed to remove a brake drum (only to have a lining of one of the shoes fall out on the floor - that can't be helping) and found a LOT of wear inside the drum.

From what I can tell the ID of the drum should have been 11", as it measures 11.007 at the opening, however it now measures 11.111 near the face and 11.222 at the worst point just inside the opening, with a rough curve to the wear pattern between those points. OD of the drum is approximately 11.5", so that is why I say a lot of wear.

I have little to no chance of obtaining a replacement brake drum, and due to the method of fitting it is unlikely that I would be able to adapt one from anything else (except maybe another forklift from the same era) so I'm stuck with trying to salvage/repair this one.

I'm not comfortable machining it out to the .222 over, as I feel it would weaken the drum too much. (The machine is 17000 lb fully laden, so I'm not prepared to take any unnecessary risks.) In fact, I'm concerned that even at the .111 over mark that it would be past the manufacturers wear limit.

My question (finally! I know, I write essays - sorry about that) is would it be feasible to reline the drum somehow?

I briefly considered weld and machine, but being cast iron I figured that the resultant nickel build up would be difficult to machine (not to mention the difficulty in actually doing the weld in the first place), so I moved on to the idea of tidying up the existing surface and then machining a sleeve to be shrink fit and then pinned inside the drum.

Does this sound feasible? Safe? Practical?

Cheers,... Jon.

Sent from my Lenovo YT3-X50F using Tapatalk

 

[FOMOGO]

How thick is the drum at it's thinnest point? I've got my Clark ready to go back together, with all new brake components less drums. Mine looked pretty good, I think mainly because all the leaking brake fluid kept every thing pretty well lubed up. You have to remember your not stopping from 60 mph. I think as long as they have some meat left they should be fine. If your concerned that truing up the drums would be removing to much strength, maybe split the difference and take half the distance, your only talking about .050 per side to even things up where the shoe will track. The new shoes will mate in pretty quickly. I wouldn't weld on them. Mike

 

[woodchucker]

You might want to find someone that does spray welding if it is worn too far. It doesn't sound like it is though. With spray welding they could build up the drums

 

[JimDawson]

The drums on my Yale were worn about 0.100 I just removed the ridge on the outer drum, cleaned up the shoes, and put it back together. The brakes hold just fine. At a top speed of about 5 MPH, I figure they'll last forever.

 

[Ulma Doctor]

in a past life- i repaired forklifts for a living,
i have seen paper thin brake drums continue to function way too far past manufacturer recommended tolerances,-on many types of material handling vehicles .
you'll be fine at a few thousandths oversize.
if you can get the brake shoe lining oversized, that would be a bonus.
otherwise make the brake drum as concentric as possible and run what you brung

as Jim pointed out, removing the ridge from the drum will ensure easier removal later on down the line

i wish you the best of luck

 

[Jonno_G]

How thick is the drum at it's thinnest point?....

I'm figuring about 1/8" at the worst point, that's why I was concerned. (11.50 OD - 11.222 ID = .258 overall or .129 per side, so just over 1/8".

I don't have brake calipers (excuse the inadvertent pun) to measure the thickness directly at the wear point, but verniers and an inside mic do the job.

You have to remember your not stopping from 60 mph.

Fair point, I just tend to be very cautious about things like this especially since I won't be the only operator. My sons will likely learn on this machine. I remember learning to drive my Dad's International tractor with no brakes, it was a nerve wracking experience.

...maybe split the difference and take half the distance, your only talking about .050 per side to even things up where the shoe will track.

That may be an option, depending on how they look after the first couple of cuts once I get them in the lathe

I wouldn't weld on them. Mike

I wasn't loving that I idea either.

Thanks for your thoughts.

Jon.



Sent from my Lenovo YT3-X50F using Tapatalk

 

[Jonno_G]

in a past life- i repaired forklifts for a living,
i have seen paper thin brake drums continue to function way too far past manufacturer recommended tolerances,-on many types of material handling vehicles .
you'll be fine at a few thousandths oversize.

Given your past experience, what would you consider to be the minimum safe usable thickness in this situation? Is 1/8" too thin, or am I just being overly cautious?

if you can get the brake shoe lining oversized, that would be a bonus.
otherwise make the brake drum as concentric as possible and run what you brung

I have a good relationship with the company that will be binding new linings on the shoes, so I can get them at whatever thickness is required (within reason).

as Jim pointed out, removing the ridge from the drum will ensure easier removal later on down the line

i wish you the best of luck

I'll definitely be removing the lip, at an absolute minimum. However the difficulty I encountered during disassembly had more to do with the fact that the inside wheel has welded itself to the hub. Once I pulled the axle and removed the outer wheel bearing I had no trouble getting the hub/inside wheel/brake drum assembly off, but I still haven't managed to separate the hub and wheel. The drum was easy, eight bolts to the inside of the hub and it lifted straight off.

Another option that I've considered is to chamfer the lining on the shoes away from the face of the drum by about 1/4" so that I don't have to machine into the corner of the drum and risk creating a weak spot at the corner.

Thank you all for your input so far.

Cheers,... Jon.

Sent from my Lenovo YT3-X50F using Tapatalk

 

[Ulma Doctor]

Given your past experience, what would you consider to be the minimum safe usable thickness in this situation? Is 1/8" too thin, or am I just being overly cautious?
I have a good relationship with the company that will be binding new linings on the shoes, so I can get them at whatever thickness is required (within reason).
I'll definitely be removing the lip, at an absolute minimum. However the difficulty I encountered during disassembly had more to do with the fact that the inside wheel has welded itself to the hub. Once I pulled the axle and removed the outer wheel bearing I had no trouble getting the hub/inside wheel/brake drum assembly off, but I still haven't managed to separate the hub and wheel. The drum was easy, eight bolts to the inside of the hub and it lifted straight off.
Another option that I've considered is to chamfer the lining on the shoes away from the face of the drum by about 1/4" so that I don't have to machine into the corner of the drum and risk creating a weak spot at the corner.
Thank you all for your input so far.
Cheers,... Jon.

Hi Jon,
caution is rarely a bad thing, especially when stopping a moving vehicle.
i agree with others sentiments, that you won't be stopping from 100 km/h
personally, i'd clean up up as best as possible, removing the minimum amount from the bellmouthed drum and run it!
all the best

 

[Tony Wells]

There is a foundry here in town that has a few hundred (seems like) forklifts running around everywhere. Back in the 70's I worked at a shop where we serviced the drums by the pile. What we did is find some mechanical tubing of the appropriate size and sliced off a piece long enough to fill the drum. Some of the drums had to be bored to straighten them out and get rid of the ridge. Then torched 3 roughly equally spaced holes in the wall, about 3/4" "diameter". We then welded with brass rod thru those holes to the cast iron drum. On the edge where the drum and liner were about the same height, we used high nickel rod and welded all around. They went on an old Bullard and were faced and bored back to original specs.
Of course, the linings were steel now, not CI, but that didn't seem to bother anyone. We did them by the pallet-load. We also did them on the trolley cars they hauled slag in on a small railway they ran internally, as well as a few other pieces of equipment. I was always surprised where they found places to put drums. I guess this was from before discs or other means caught on.

 

[hermetic]

I think I would be tempted to fabricate a new one in steel if you can get your hands on some large enough tube. Circular flat plate with a peice of tube welded to it, then bore to size. Any good commercial vehicle brake specialist will reline the shoes for you to pretty much any thickness within reason. If you are really not happy with the cast drums, that is the way I would go, at the speeds you will be doing, the difference in coefficient of friction between cast and steel will be negligible.
Phil