Welding two flywheels together - PeachParts Mercedes-Benz Forum

Simpler=Better · #1 03-29-2012, 10:27 AM

This is for my FordCedes project...

It seems the easiest say to mate my Ford transmission is to machine the Ford flywheel down and weld it to the 617's auto flywheel, balance, and install. Does anyone see a problem with this plan?

bigblockchev · #2 03-29-2012, 10:58 AM

The only issue I see is maintaining accuracy in the post weld situation. If your welder is very good and keeps the distortion to a minimum it might work. Post weld heat treatment / stress relieving might be a good idea. New territory to be explored mechanically! There is a lot of energy stored in that flywheel , drag racers use hydro formed bell housings and kevlar blankets to contain flying bits.
If it can be done well then it will probably work. Cheers Dan

Simpler=Better · #3 03-29-2012, 11:13 AM

I'm going to be machining the Ford flywheel so that it presses into the Mercedes flywheel-so alignment shouldn't be an issue.

Walrus · #4 03-29-2012, 11:45 AM

Quote:

Originally Posted by Simpler=Better

I'm going to be machining the Ford flywheel so that it presses into the Mercedes flywheel-so alignment shouldn't be an issue.

If you can do this, why not drill, countersink, and bolt. Much less heat and distortion. Remember also, if you can machine close enough tolerance, you may be able to freeze and press-fit like the ring gear for the starter is done...

Simpler=Better · #5 03-29-2012, 11:54 AM

I can get the bores to be pressed within 0.0005" no problem. I just don't trust a press fit.

I'd bolt it together, except the Mercedes auto flywheel is extremely light-it's maybe 3/16" thick-I don't really trust it.

I'm hoping to use the Mercedes to engage the stock starter, and then basically weld the Ford friction surface onto it-making a frankenflywheel that will easily bolt up to my Ford transmission.

t walgamuth · #6 03-29-2012, 12:25 PM

l would seek the advice of a very experienced machinist/welder. My favorite machinist and i have discussed adding weight to 240d flywheels. Although he is an excellent welder, welding was not something he considered. For that reason I would be cautious about this idea.

Remember the automatic flywheel is only designed to transmit starting load from the starter, not drivetrain stress.

Stretch · #7 03-29-2012, 01:22 PM

What sort of cast iron are these Mercedes flywheels made out of anyway? Are they "weldable"?

I've got a reference book somewhere that states certain types of cast iron are not to be welded. If I remember rightly there was something about HCP structures and internal stresses - but don't quote me on it. I'll try and find that text book.

In the mean time there's some useful practical information here

MIG Welding Cast Iron

whether you'll be able to adapt it to flywheels or not is another thing though.

Simpler=Better · #8 03-29-2012, 01:32 PM

I was under the impression that the flywheel was steel, the finish seems considerably brighter than machined cast iron. I might be able to find a way to bolt it up, the Ford flywheel is oddly shaped and protrudes quite a bit more than the 617's flywheel.

Stretch · #9 03-29-2012, 01:47 PM

Quote:

Originally Posted by Simpler=Better

I was under the impression that the flywheel was steel, the finish seems considerably brighter than machined cast iron. I might be able to find a way to bolt it up, the Ford flywheel is oddly shaped and protrudes quite a bit more than the 617's flywheel.

Oh right - I thought it was cast iron. Does anyone know for sure?

Simpler=Better · #10 03-29-2012, 02:32 PM

I'll hit them both with the grinder when I get home and report back.

charmalu · #11 03-29-2012, 02:57 PM

You mentioned the MB auto FW, but didn`t say if the Ford FW is also for an automatic.

When I first started reading through this, I was thinking manual FW and machining and mating two manual FW together.

You want to mate two auto FW`s, or two Manual FW`s, or a combo of auto and manual?

I have a 240D manual FW and a 300 617 FW, and they are steel, not forged.
the auto FW does look like it is a forged one, but don`t have a spare at the moment.

Charlie

Nate Stanley · #12 03-29-2012, 03:07 PM

Not exactly the same situation, but I'd like to share some insight about welded flywheels, YMMV.

I used to be heavily into Corvairs. They came with a 3-pc sandwich flywheel with the flange that mounts to the crank in the center, pressure plate on one side, and a steel backing plate on the other.
This was riveted 14-16 places around the perimeter.
When the rivets lost their tight fit, a popular fix was to weld all 3 layers together and have it rebalanced.

I installed one of these welded flywheels in my '65 convertible and my brother and I headed off to Canada. On the way back, in Idaho, I was greeted with a huge banging noise deep in the engine. Tearing the crakncase cover off the top by the road, we discovered a broken crankshaft right inside the crankcase wall.

The original design of the riveted flywheel allowed some damping of minor harmonic vibrations, and the welding made the assembly so stiff that the vibrations ended up heading past the first main bearing journal on the crank.

Later, back in San Jose, I changed to a bolted flywheel and never had a pro blem again.

So be sure to look into any secondary vibration damping that was designed into either flywheel design.

OM616 · #13 03-29-2012, 03:24 PM

I am the first to be skeptical of anyone who proclaims them selves as an authority on anything, that being said,....as an experienced welder and machinist, welding two fly wheels together is not a good idea.

When I was in high school I worked at a shop with a guy with a limp, one day I asked him what happened to his leg, he said that a clutch come apart at 9000 RPM as he was coming off the line, even with a scatter blanket it still just about cut the car in half.

The moral of the story is, the job of the flywheel is to store and transfer energy, should ANY part of it fail, that energy is released rapidly.

Lets say that both wheels are made from weldable steel, the welds alter the temper of the material surrounding the weld, which alters its strength, and it also puts stress into the wheel as the weld pulls the material together unevenly. A good weld will fail by the material it is welded to yielding next to the weld, where as a bad weld will fail along the center of the weld.

The fly wheel flexes and twists, even the little 617 will. One needs to consider should the welds fatigue and fail, what will result?

Even one piece cast flywheels can fatigue and grenade, seen that too.

The best safest option is to have a custom fly wheel made, but that will cost some money, where as you might be able to get the weld option done for a leg.

Simpler=Better · #14 03-29-2012, 04:53 PM

I was thinking of taking an auto 617 flywheel and leaving in unchanged. I would then take the manual flywheel from the Ranger and machine it to be welded to the Merc auto flywheel. This way I would be using a standard Ford pressure plate assembly and friction surface.

I can make up a custom flywheel if I need to, or look around and try to find a 240D flywheel/ clutch assembly.

The welding plan doesn't sound so great anymore...

junqueyardjim · #15 03-29-2012, 08:38 PM

I just really can't imagine anyone trying that move, of matching and welding a manual clutch flywheel to the very light weight automatic flywheel. They aren't built for that kind of use. I have an extra flywheel and clutch, PM me if you are interested.