You're welcome! Thanks for blazing the trail on this idea.

The new pedal looks great. I'm looking forward to your results on this. I think the pedal ratio you've chosen should give the results you're (we're) looking for.

One advantage to the new ratio is you now have the ability to tune the pedal feel with different master cylinder bore diameters. If the travel is too much and the effort is low you could increase the master cylinder size from 19mm to 21mm or 23mm. You can also play with quick take up master cylinders.

__________________
1969 220D 5 Speed (OM616)
1983 240D 4 Speed
1985 300D Auto 376K
1985 300D Auto 275K

Not sure if I got carried away or not. I could easily do a 6:1 ratio, but with around a 3/8" "hole" -- actually half moon like grove cut into the pedal assembly -- I can easily get the 9:1. I can always change it down the road. The brake light switch was super easy to create a guard or stop. A 90* piece of metal and the spring is now mounted to a bolt. The other end of the bolt will hold the 90* piece which is in the making. It actually turned out a lot neater and nicer than I originally thought.

The current mock-up needs some fine tuning right now. I need to shift the MC right around 1/8" to maybe 1/4". The front plate is too thick since I can slim it down to around 1 1/4" max and still have the same stroke.

I acquired a 9:1 pedal ratio. OEM was 4:1. So, assume 75 foot pounds, its:

4x75=300
9 x 75 = 675

I'm sure all the engineers will come out of the wood work and tell me how the above rule of thumb is not really correct ... lol. However, all the big names in manual brakes / brakes use this as their example, so it's fine with me. lol. As for the amount of force created by the diaphram (brake booster), I am getting numbers all over the place with the different calculators. Does anyone out there know?????

In any event, this weekend and a few hours I should be ready for the re-install. Need to figure out if I want an adjustable pushrod (simple screw like gizmo) or do I measure up and go with only one size fits all ??

Attached Thumbnails

   

If you go with 9:1 your effort will be reduced but travel will increase. Brake feel is best when the pedal is modulated by force rather than travel so I would think you should shoot for the highest effort you can safely maintain.

Also, as the ratio increases the master cylinder pushrod stroke is reduced. Reduced stroke becomes a problem in the event of a front or rear hydraulic system failure. When everything is working correctly a column of brake fluid from the rear piston pushes the front piston. Even with reduced stroke your brakes may work fine. However, if one hydraulic system fails the associated piston will go to the end of it's travel. Either the rear piston will collapse until it mechanically contacts the front or the front will collapse until it hits the end of the cylinder. No matter which one fails the stroke required doubles. For safety you need to have enough stroke to fully activate the working piston when the other piston collapses. That may cause you to relocate your pivot point back to 6:1. If stroke is ok you can adjust travel with increasing master cylinder size as I mentioned before.

In the end no matter what you do you'll need to generate a specific hydraulic pressure at the calipers to get the desired stopping distance. I don't mean the pressure required to lock the brakes. I mean a range of pressures where the required effort at the pedal for a hard stop can be developed and maintained without adding another foot or locking your knee. You have an advantage over Mercedes as you can tailor this to your needs rather than the needs of lowest common denominator. In my opinion the lowest useable travel is will give the best feel.

I know you have the w126 big brake mod and stainless braided hoses but what other mods have you done at the caliper end? Different brake compounds and caliper types can reduce effort too. Anything you can do to reduce hydraulic pressure and flex will allow you to make a better compromise between effort and travel.

An adjustable pushrod would be a good idea. Especially if you start changing master cylinders or pedal ratios.

__________________
1969 220D 5 Speed (OM616)
1983 240D 4 Speed
1985 300D Auto 376K
1985 300D Auto 275K

Currently I have a full pedal stroke. What I mean is that the brake pedal lines up perfectly with the clutch pedal and if I push the brake pedal, I get the full "push", which is around 3" or 4". First, I was affraid they were going to be different after the pedal arms were spliced together, so that was a pleasant surprise.

Also, I can change the plate thickness or the location of the pushrod. If I drop the pushrod down 1/2", then it's 13.5/2 = 6.75 ratio or another 1/4" to get 13.5/2.25 = 6.0, so that 3/4" may or maynot equal the sweet spot. The plate thickness can go from its current size all the way down to around 1".

I think the first thing is to make an adjustable push rod. Then, drill another hole for the 6:1 ratio. That way, I can install that to see how I like it. That does not require any drilling of the 3/8" "half moon" into the pedal assembly housing.

I think that's a good plan. You should be able to dial it in nicely.

As long as you can get the full stroke on the master cylinder you'll be OK. That part is crucial in the event of a brake hydraulic failure.

__________________
1969 220D 5 Speed (OM616)
1983 240D 4 Speed
1985 300D Auto 376K
1985 300D Auto 275K

That was the shocker with the spliced brake pedal. I was bracing myself for some sort of odd angle / positioning where the push rod only goes around 2". However, I currently have a full stroke with the jumbo plate. I tried measuring the stroke or push on my DD, and it's around 4" Actually, I have 2 methods of adjustment: The plate thickness and the pushrod. Since I can achieve a 9:1 ratio down to 6:1 ratio, I am thinking there's the "sweet" spot in that range.

The adjustable pushrod was pretty easy overall. I just wish I could drill a perfectly straight bore hole. This is proto-type #1. It works, but the final one will have to be on a lathe or some sort of gizmo which centers and goes straight with the hole. Taped a 8mm x 1.25 threads about 1"+ down. Final one will go almost all the way down. I'm thinking a 1" or 1 1/16" thick plate and a slight shift of the MC to the right and it's done to test the 9:1 ratio. It's going to be the "perfect" solution or too much. Either way, there's light at the end of the tunnel now for manual brakes -- and again, many thanks to VT220D for the brake pedal arm solution.

Attached Thumbnails

   

Not to change the subject, but I just had an idea. If you have an electric water pump and a block heater, could you hook up the water pump to cycle periodically while the block heater is on to circulate the warm coolant around and heat the engine more effectively?

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

First, I am an electrical dumbo. The juice for the block heater is A/C and the EWP is D/C, so I don't think so unless you did some fancy footwork. However, once you shut the car off, the EWP and fans do run at full blast for 2 minutes, which is supposed to get rid of any heatsink and prolong the engines life.

Jooseppi: you would be proud of your pedal assembly. It has fulfilled it's R&D mission. I am literally about 1 day away from manual brakes where I have a full stroke and 9:1 pedal ratio.

I think the bypass flow through the radiator would act as a heat sink and lower your overall temperature. Parking heaters like the Webasto ThermoTop EVO 5 do use a water pump but they also put out 5KW of heat. The average block heater is only around 1KW.

Another problem you'd have is water pump power consumption. If you use your auxiliary water pump you'll need a 12 volt source that can run for the long period of time needed by the block heater. Even using periodic cycling the total time would be significant. The Webasto also runs on 12 volts but 5KW gets the job done in about 20 minutes.

Either way it might be an interesting cheap experiment. Temperature could be monitored at the engine temp sender using an ohmmeter for better low temp resolution. VDO publishes the temp/resistance chart for these online. You could run the pump from a 12 volt supply cycled by a simple relay circuit and a 555 timer. You could also run it continuously at first and then lower the duty cycle until you hit the sweet spot. A lower average temp with a more even distribution might give better cold starting. If you can get the head to 40 degrees it will start.

Another idea is dual block heaters and a pump for rapid warm up.

__________________
1969 220D 5 Speed (OM616)
1983 240D 4 Speed
1985 300D Auto 376K
1985 300D Auto 275K

You can drill a centered hole with a drill press:

1. Put the workpiece in the chuck, and clamp the other end in your vise.
2. Clamp the vise to the table.
3. Release the workpiece from the chuck, and insert your drill bit.
4. Voila!

In addition to the block heater, the ultimate gucci setup is ot have a battery tender under the hood as well, so it's at a full 14.4 when you go to crank instead of the settled down 12v.

__________________
$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Who would have thought that MB had so many variations of so many different parts, or at least the the balancing disk, vibration damper, and pulley hub?

I will get some snappies tomorrow, but the current project on the front burner is the 1 belt to 2 belt conversion for the NA (naturally asperated - non-turbo) engine.

The original set-up was a really thick vibration damper with a deep nosed pulley hub. This appears to permit the pick up for a tach, assuming one wanted one. I appreciate the 300D NA had the giant clock deal, so the pick-up was for other items but it's a nice "option" for a tach.

I now have the other (2nd) flavor for the NA: a larger, thinner vibration damper more similar to the turbo set-up and a pulley hub which is about 2mm or 3mm away from fitting perfectly down into the vibration damper. The bad thing is no more pick up if you want a tach with the OEM set-up.

Not sure there is a 3rd or more flavors for the NA engine.

The turbo set-up is totally different than any NA engine set-up and I am thinking there is only one set-up with the turbo engine.

Further, it appears that none of the items are interchangable.

Getting the pulley hub machined and welded and balanced tomorrow, assuming no problems. The only issue I now see is the 10mm belts with the 2 belt deal is a little thinner than the NA original set up, but I doubt that will create an issue.

Overall, a pretty simple project I am hoping ....

Daughter heads back to college today, and I've got a "wait" before her flight, so I decided to jump sequence on projects and rebuild a lift pump. There's a number of threads on the topic, and Stretch did his usual fantastic job documenting the build on the "M" pump / non turbo / 2 dog ear'd lift pump.

This covers the 3 dog ear'd pump found on the "MW" pump -- and yes, the turbo engine is nearing completion. I could not find anything on the rebuild, so this is how I did it.

Overall, this is a really easy project. I would say collectively an hour for everything. No special tools, except a dental pick. I would venture a guess that this is something which should be done every 10 years. The kit costs $6 bucks, and the O rings are pretty cheap too. Not pictured is the gasket to mate the lift pump back to the IP and the black handled Bosch primer pump. Both of those are under $20.

The starting point is clean parts. I would say there was around a table spoon of goo, rust crap, and other stuff inside the body of the lift pump. This was a JY IP with lift pump so I am not surprised. It took a full 50 minute cycle in the ultrasonic cleaner to clean it up.

Here are some pictures.

The parts
The kit
The "head" -- not sure the technical name, but it's the part which goes inside the IP
And the "O" ring. The old "O" ring is picked out and the new one is pushed in. I used a phillips head screwdriver to glide it into the grove. The steel pushrod goes in after the "O" ring is inserted. The "O" ring fits inside a grove which is about impossible to take a picture of. There was a noticable difference in pull or drag on the push rod after the new "O" ring was installed.

Attached Thumbnails

         

The "head" is held in place by a metal tang-like climp. The push rod slides thru the hole, and I suggest some sort of lubricant since the pieces might flash plus you want something to lubricate the inners before the oil gets in there from the engine

On the other side is a cup which reminds me of the older style wheel calipers. Slides right in and again a little lube. You can see where the end of the push rod mates to the inside of the cup.

The head goes in, and the metal tang goes into place. The metal tang holds the head.

Again, everything goes back together as it was taken apart. The parts are really "self-explanatory" in that there's only one way for them to fit and it's an overall simple design.

Once the head is held in place with the metal tang, install the spring with metal cap with copper crush washer. This requires a little "umpf" but no biggie.

Attached Thumbnails

         

The kit itself consists of 6 pieces: 2 springs, 2 valves, and 2 copper crush washers. Again, pretty self explanatory. They all fit exactly the way they looked when you took it apart. They only fit one way and there's a grove for the spring. Overall, pretty easy and this should save those weak lift pumps. Since my DD still has the NA - non-turbo engine, I plan on rebuilding that pump as well, and I will be copy-katting Stretch's thread on the topic.

Attached Thumbnails