How do you stop a m809 if the brakes fail?

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319cssb

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Oh yeah i remember seeing brakes like that on mud trucks. I think they do that as the wheel brakes usually are wet and full of dirt. That sounds like a great option. I gotta google that.
 

98G

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Hm. They ain't all that and a bag of chips. Mainly, I was curious about them as a better parking brake and *maybe* an e-brake in case of service brake system failure.
Consider the rear diff ratio of 6.44:1. This makes a pinion brake useful only for very low speeds (which is where you see them used....)

Using a pinion brake to try to make an emergency stop from even 45mph will just illustrate how kinetic energy will transform into heat and melt it. There's just not enough room under there to fit in enough mass to absorb the heat.

Full airbrakes are much to be preferred. Second to that would be a dual circuit (not available for 809series).
 

319cssb

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Speaking of 809 , where can i find definete information about the model years. I just saw a 1988 (whaaaaa???) M813A1.
someone said something about models being still produced after the model ended. I can see that happening for a year maybe . But 6 years?
 

98G

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Speaking of 809 , where can i find definete information about the model years. I just saw a 1988 (whaaaaa???) M813A1.
someone said something about models being still produced after the model ended. I can see that happening for a year maybe . But 6 years?
I speculate that manufacture dates on the data plates were occasionally changed when going through rebuild. I've seen
Manufacture dates on 939A0series trucks as late as 2007.

And we drift off topic.....
 

Robo McDuff

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Saw this old thread while looking for info. Might as well reply and add my question/suggestion.

Biggest problem of ALL M39s and M809 (the old 5-tons) is that they are single circuit. One leak and no breaks. A lot of threads about that. Standing on any hill or going with any speed and you will continue to roll. For those preferring air brakes, those are , to my knowledge, always double circuit, so

Emergency brake fully primed and adjusted perfect is nice to slow or stop at low speed, but hat one is not going to do much in an emergency.

In 2012, I was pondering the same thing, and we had a thread on making a dual system for an old 5-ton. We even discussed how to split the brakes: front vs back, front + 1 mid, rear + 1 mid, and several other combinations. It never went to the practical realization, and to my knowledge nobody yet did this. We also discussed putting retarders or Jake brakes in there. Would seriously help reduce speed, but again not enough for an emergency.

Probably those preferring double circuit air brakes just bought a 900 series 5-ton. The rest is trying to keep their systems as good as possible while praying for no accidents (or a lot of priusses).

Suggestion and question involving the hand brake.

At one Dutch surplus scrap yard, I once saw an old 5-ton with the emergency brake being activated through an air brake system as opposed to the normal cable connection to the hand brake lever in the cab. So the brake shoe and everything is the same, only the cable is replaced by an airbrake.

They told it worked good.

No air: brake is fully engaged. Leak in air system: brake slowly or quickly engages, depending on the size and location of the leak. For the rest, it is controlled by a lever similar to a trailer brake. Getting the parts would not be so expensive.

My question is, in case the hydraulic system fails, would this airbrake work good enough to slow or stop the truck with normal speeds (20 - 40 mph). Maybe the better question is, is that drive-shaft brake system (shoes and drum) strong enough to deliver the brakoing power without ripping up the brake drum or would it just disintegrate very quickly.
 

gringeltaube

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Answer is NO. It's still the same old drum brake and shoes, and it would quickly overheat to the point where you have zero brake effect left.

It was designed- and may be good enough- as a parking brake, but not as an emergency brake.
 

Robo McDuff

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Thanks for the clear answer. It's what I thought but I was hoping against hope ...

Seems the only way how to really solve this problem is to figure out which commercial dual MC can handle this, install a second air pack, maybe even a third air tank, and split the brake system.

As to splitting, I was looking at the front brake system, see it is would be possible to install a second brake cylinder down and each cylinder operating one shoe. It would be probably technically possible, with one circuit operating the front down cylinder on both front wheels and one rear axle, with the second circuit operating the top front cylinder and the other rear axle.

However, in Europe that would mean to have the system rechecked by the DoT, and the modification and checking costs would almost certainly be higher than selling your truck and buying a 900 series truck.

Anyway, that would probably always be the problem with any modification on the brake system: obligatory check, even if it is improvement, and unless you get an approval, you will get problems with the insurance as well.
 

Lovetofix

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Or just replace/rebuild ALL the components, replace the hard lines with cunifer, get new rubber lines and then you know your whole system is good to go (Er STOP).
My 1972 M817 brakes were still operating just fine after 38 years so it can’t be THAT wimpy of a system providing everything is maintained well. I am happy with knowing everything is new and will do brake inspections regularly. It’s not that hard to pull a hub once all fasteners get loosened up.


Sent from my iPhone using Tapatalk
 

Robo McDuff

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Completely agree, ... but.. I would trust maybe a 30 year old system a lot better than generic Asian replacement stuff including lines. So you have to make sure that all is replaced or overhauled and all with high quality stuff.

And that was before I read more here about sudden brake failure even with completely overhauled stuff.

I replaced all lines in 2011, while still in the Netherlands. Did not do the brake cylinders because I did not know how long the truck would stand still again.
Just did one brake cylinder. the one I suspected was a problem. It was, overhauled it and today we are going to fill up and test the system.
 
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