The Sleeper Part Deux - Page 22 - PeachParts Mercedes-Benz Forum

VT220D · #**316** 10-22-2014, 09:47 PM

Quote:

Originally Posted by greazzer

Once I track down a W115 I can figure out the best place to splice the two -- I think you're 100% correct. As for the stop, are you talking about the pushrod? The push rod travel is limited to around 3+". It's definintely not 4". The MC has a "tube" in which the push rod end enters. Around 1/2" of the pushrod permantently rests in this tube. On the W123, if you fully depress the brake pedal arm, it will eventually hit the assembly housing. However, the rod does not go more than 4". Is that what you mean by a stop?

What I mean by stop is the return stop. If you look at the first pictures I sent of the W115 and W123 pedal setups with the power brake booster you can see that the booster limits the pedal return. Without the booster the pedal comes back too far and stops against the brake light switch. That part was not designed to take the stress.

With a 1/2" inside the tube your pushrod won't fall out but the brake switch may end up being destroyed. Every time you sidestep the brake and let it return with full force it will hit the switch. If nothing else you may loose your brake lights.

As an example: In early W115 cars the parking brake pedal rubber stop would fail. The parking brake switch and bracket would become the new stop and eventually break right off. The dash warning light would then stay on all the time since the switch was just hanging there. Later cars got a revised stop and this was prevented.

If you design your bracket for the correct pushrod to cylinder clearance without first making a return stop the pedal will be too high and the brake switch will likely be damaged. If you add a stop later your master cylinder will be too close to get the correct pushrod clearance requiring you to shorten the rod or shim the master cylinder.

The stop itself could be a bracket with a rubber bumper or slotted plate that works with a welded stop on the pushrod. It would be interesting to cut open a power brake booster and see how it's done internally.

VT220D · #**317** 10-22-2014, 09:50 PM

Quote:

Originally Posted by greazzer

One other measurement please:

If you attach the W115 brake pedal arm to the W123 assembly, and measuring from the inside of the actual "pedal" part (where the rubber pad or covering goes) of the brake and clutch, what do you get?

I posted before I saw this. It's about an inch at the closest point with the rubber removed. It would be unworkable as is and bending the W115 pedal will just make it even shorter and undo all your mechanical advantage.

If you decide to splice get the more common w114/115 automatic pedal arm. You'll just cut the wide pedal off anyway. I may have a W115 automatic pedal I can donate. I don't usually keep automatic stuff but I remember seeing one.

greazzer · #**318** 10-23-2014, 09:10 AM

PM SENT !

greazzer · #**319** 10-23-2014, 09:15 AM

Quote:

Originally Posted by VT220D

What I mean by stop is the return stop. If you look at the first pictures I sent of the W115 and W123 pedal setups with the power brake booster you can see that the booster limits the pedal return. Without the booster the pedal comes back too far and stops against the brake light switch. That part was not designed to take the stress.

With a 1/2" inside the tube your pushrod won't fall out but the brake switch may end up being destroyed. Every time you sidestep the brake and let it return with full force it will hit the switch. If nothing else you may loose your brake lights.

As an example: In early W115 cars the parking brake pedal rubber stop would fail. The parking brake switch and bracket would become the new stop and eventually break right off. The dash warning light would then stay on all the time since the switch was just hanging there. Later cars got a revised stop and this was prevented.

If you design your bracket for the correct pushrod to cylinder clearance without first making a return stop the pedal will be too high and the brake switch will likely be damaged. If you add a stop later your master cylinder will be too close to get the correct pushrod clearance requiring you to shorten the rod or shim the master cylinder.

The stop itself could be a bracket with a rubber bumper or slotted plate that works with a welded stop on the pushrod. It would be interesting to cut open a power brake booster and see how it's done internally.

I had to chop my vacuum booster apart to be able to make the plate and to understand the mechanical aspect of it. It actually has 2 push rods. The one you see and another which looks like engine valve. They are back to back when inside the booster. There's a super heavey duty rubber diaphram with some springs inside. I think I kept almost all the internal pieces, so I will post a picture tonight. The booster is clearly an item which was made and designed not to be taken apart. I am guessing for safety reasons. I got a cut off wheel and in about 20 minutes, I had the pieces I needed to make the plates.

VT220D · #**320** 10-23-2014, 01:40 PM

I'd like to see those pics. The stop design used in the booster might be the way to go.

BTW: I have the part and I replied to your PM.

greazzer · #**321** 10-23-2014, 02:25 PM

Quote:

Originally Posted by VT220D

I'd like to see those pics. The stop design used in the booster might be the way to go.

BTW: I have the part and I replied to your PM.

I responded to the PM. THANKS !

Here's some snappies. I cannot locate the springs or the super thick rubber inside diaphram. Pic #2 is the push rod which looks like a valve. The alum piece is the vacuum pump block off plate. Most of the pieces are there.

VT220D · #**322** 10-23-2014, 10:55 PM

Thanks for the pics. I still can't really tell what provides internal stop for the pushrod. There must be something that prevents it from coming out of the booster. I'll try to find a cross section diagram in the manual. Maybe that will clear it up for me.

The vacuum pump block off is awesome. Did you make it? Can you get another one?

Even if I go with an electric pump and conventional booster I'll need a block off cover. I've tried to find them on German Ebay but they're always attached to an expensive engine. I've added some pictures of them. They seem to be most commonly found on bootsmotor (boat engine) or gabelstapler (forklift). They were also found on early OM621 engines in drum brake W110s or Pontons. I've been looking for a while. Your solution is probably best.

t walgamuth · #**323** 10-24-2014, 06:02 AM

Quote:

Originally Posted by VT220D

Thanks for the pics. I still can't really tell what provides internal stop for the pushrod. There must be something that prevents it from coming out of the booster. I'll try to find a cross section diagram in the manual. Maybe that will clear it up for me.

The vacuum pump block off is awesome. Did you make it? Can you get another one?

Even if I go with an electric pump and conventional booster I'll need a block off cover. I've tried to find them on German Ebay but they're always attached to an expensive engine. I've added some pictures of them. They seem to be most commonly found on bootsmotor (boat engine) or gabelstapler (forklift). They were also found on early OM621 engines in drum brake W110s or Pontons. I've been looking for a while. Your solution is probably best.

How about on a thermo king reefer unit? Probably still some of them around.

greazzer · #**324** 10-24-2014, 07:58 AM

Last night, I see precisely what you mean by the arm going back too far and hitting the push button brake light switch. In a total OEM application, the stop is created by the booster since the diaphram can only go "in-and-out" so far, thus limiting both push rods in their travel. On the modified one, there's a few convienient places for a stop. So, that's EZ.

Yes, that MB plate is a killer. It's over $400 new, so that is why I figured out how to make one. It's $100 shipped CONUS. The only tricky part is sourcing SY aluminum since new is around $100 just for the stock. Right now, I have 2 configurations of that plate, one with a thick flang and one with a flang which mimicks the OEM vacuum pump. Both work just fine.

VT220D · #**325** 10-24-2014, 11:21 AM

Quote:

Originally Posted by t walgamuth

How about on a thermo king reefer unit? Probably still some of them around.

Great idea. I know they used the OM636 but did they also use the OM621?

funola · #**326** 10-24-2014, 11:24 AM

Quote:

Originally Posted by VT220D

Great idea. I know they used the OM636 but did they also use the OM621?

Is this to get a vacu pump cover? How about gut an old vacuum pump? Perfect cover.

VT220D · #**327** 10-24-2014, 12:51 PM

Quote:

Originally Posted by greazzer

Last night, I see precisely what you mean by the arm going back too far and hitting the push button brake light switch. In a total OEM application, the stop is created by the booster since the diaphram can only go "in-and-out" so far, thus limiting both push rods in their travel. On the modified one, there's a few convienient places for a stop. So, that's EZ.

Glad you saw it. It should be simple to come up with a good stop.

The master cylinder in the W123 and W115 is 19mm which makes it difficult to reduce diameter. I'm sure that's why you're relocating the pivot. There are some 17mm diameter cylinders but they aren't common.

However, there are some stepped bore ATE cylinders used on later Mercedes and other applications. The stepped bore cylinders use a larger rear piston to take up clearance. You may be able to use one of these to keep your pedal from sinking too low. They can be found in many newer cars. Check out this link for more info:

http://www.omnihydraulik.de/mediapool/135/1358817/data/MASTER_CYL._WITHOUT_BOOSTER_.pdf

VT220D · #**328** 10-25-2014, 10:50 PM

Quote:

Originally Posted by funola

Is this to get a vacu pump cover? How about gut an old vacuum pump? Perfect cover.

True. That's what I'll likely do initially but I like the finished appearance of a cover. I'm still a long way from needing it!

greazzer · #**329** 10-26-2014, 04:17 PM

Very little done this weekend.

I did finally start perhaps one of the most important aspects of this project: electrical. Since I am a total noob with car electronics, it has been painful to say the least. I have, however, wired and re-wired a few houses, so I borrowed heavily from that knoweldge.

I got the fuse box I am happy with. It comes from a turn of a century Buick. Holds 8 of the jumbo fuses. The 2x 20 Amp are for the 2 fans which will be going in shortly. The leads are OEM from a few Buick donors. They have what appears to be Delphi connectors #12065915, and the red wires fueled 40AMP appliances so I am guessing I am in good shape since almost everything I got is 10AMs (except the 2 fans). I will be using Deutsch connectors for the remainder.

The relay holder and relays are from a Nissan. It holds 6, which should be perfect for what I am doing. The fans will be sharing a relay and the WVO solonoids will be sharing one too.

Both boxes have that "universal", blend in the background look to them which is what I was striving for since that is what MB did back in the day.

Thanks goodness there is a junkyard less than a 1/2 hour from my house ... lol. Once my mil spec wire, crimpers, and other Deutsch items come, I am hoping to have one full day of electrical fun.

Maybe JayBob will volunteer to check out my workmanship if I drive over to his house ...

greazzer · #**330** 11-05-2014, 10:11 PM

A zillion thanks to VT220D for the pedal arm and info. I found about an hour tonight to tinker with it and I am shocked at how little now needs to be done. I have achieved the following: the flagship 6:1 ratio versus the stock 4.11:1. Further, because of how the spacing is increased, the pushrod is much longer. As a result of that, I will get a full "push". The mock-up is reassembled. My very brief experiement with manual 4+:1 ratio was the almost "there" solution, so I am positive that after I re-do the adaptor plate, spend around 5 minutes re-grinding a few areas, figuring how I want my stop (the pedal lines up almost perfectly now) this project will actually be done. The EVP along with the manual brakes are 2 major R&D projects to be done. Although I wasted about a year piddling around, it's only been around 3 full days collectively that was invested on these two, give or take.

What's nice is that I am thinking I can complete the pedal arm and a gizmo or two, and this conversion is something which will just require the pedal arm mod to slip on and off, along with the spring and stop plate gizmos and about 5 minutes of grinding. The aluminum block which goes onto the fire wall is a slip on deal also.

Thanks again to all those folks who contributed !!!! VT220D, Mr. Luna, et cet.