Clutch Fork

[Dabbler]

You have low temp SS?

 

[Tom O]

@PeterT : what a great offer doing the CAD file. I think i am going to take you up on that, just to see how much it would be. Once i have the new fork made, we can see what you would need in order to design the part.

As far as the fork itself: i decided to make it out of steel with bronze wear pads. The pads will be silver soldered on. This allows me to use bronze that i have on hand. The steel will give me high strength. If,at some time in the future, i have casting capabilities, i will consider using this new fork as a mold and remake it out of bronze.

I decided against a repair because the fork is just such a poor fit. Also, reading on various welding forums, heating up bronze for brazing can be problematic since the alloying elements melt at different temperatures and quite often one ends up with a structurally weak spot. Silver soldering foregoes that problem for the most part. So if i’m going to silver solder, i may as well solder bronze onto a well fitting fork made from steel...

More on my progress soon...

I think I’d try to get it built up on the pads using tig to control the heat better, by the looks of it repairing the space between the pads wouldn’t matter as it normally would not touch.

 

[PeterT]

Is this recess necessary for clearance to some part of the shaft assembly or just the way they made it?
If not, seems to me you could replicate the donut housing out of steel & just face it with say .050" sheet bronze like a veneer. You would have substantially more surface contact area & maybe get away with high quality retaining compound (Loktite) vs. silver soldering. The trick is know before it ever wears it through but maybe you would feel that somehow on the lever? Or am I misunderstanding & the sliding also occurs on the outer shoe/lip?

Also what is the purpose of the pin? Does it have to be bronze or it just made sense for them to integrate into the casting?

 

[Janger]

@PeterT : what a great offer doing the CAD file. I think i am going to take you up on that, just to see how much it would be. Once i have the new fork made, we can see what you would need in order to design the part.

As far as the fork itself: i decided to make it out of steel with bronze wear pads. The pads will be silver soldered on. This allows me to use bronze that i have on hand. The steel will give me high strength. If,at some time in the future, i have casting capabilities, i will consider using this new fork as a mold and remake it out of bronze.

I decided against a repair because the fork is just such a poor fit. Also, reading on various welding forums, heating up bronze for brazing can be problematic since the alloying elements melt at different temperatures and quite often one ends up with a structurally weak spot. Silver soldering foregoes that problem for the most part. So if i’m going to silver solder, i may as well solder bronze onto a well fitting fork made from steel...

More on my progress soon...

Keep posting on the 3D metal printing of this part boys that’s pretty interesting. View of the future.

If you guys do finish a cad model I could print a sample for fitment. I just need the .stl file.

 

[Janger]

Just catching up on my Youtube channels. Interesting one by Tom Lipton venture into 3DP metal. Happens to be a different alloy for his purpose but got me thinking about your clutch fork. I have zero experience with Shapeways bronze in terms of suitability to this application. But company wise, my one & only plastic part order came through reasonably priced with no drama. I wonder if it was printed slightly oversize to compensate for any 3dp striations & allow final machining dressing allowance might be competitive option to a chunk of bronze stock from scratch since the overall volume isn't too great. I don't have a good feel if the sintered material would be as good as stock alloy in this maybe kind of heavy application. Some have mentioned 3DP metal has micro porosity. I will do the CAD file to obtain price estimate if you are game.

material
https://www.shapeways.com/materials/bronze

video

$78 bucks for a custom handle printed in metal. Wow. And Tom said it would take him a day to make. So saying $75/hr for machining * 8 hours = $600 part.

 

[RobinHood]

You have low temp SS?

Yes i do.

 

[RobinHood]

I think I’d try to get it built up on the pads using tig to control the heat better, by the looks of it repairing the space between the pads wouldn’t matter as it normally would not touch.

Considered that. My TIG skills are not up to par yet. Need way more practise. May still do it though, but with a steel fork body and just wear pads in Si Bronze.

 

[RobinHood]

Is this recess necessary for clearance to some part of the shaft assembly or just the way they made it?
If not, seems to me you could replicate the donut housing out of steel & just face it with say .050" sheet bronze like a veneer. You would have substantially more surface contact area & maybe get away with high quality retaining compound (Loktite) vs. silver soldering. The trick is know before it ever wears it through but maybe you would feel that somehow on the lever? Or am I misunderstanding & the sliding also occurs on the outer shoe/lip?

Also what is the purpose of the pin? Does it have to be bronze or it just made sense for them to integrate into the casting?

The recess is mainly the way they made it. The wear pads are at the tips. That is pretty much standard clutch fork design universally. Some also have a third contact pad in the area of the pin.

Donut housing: You mean like this?

On the right is the new fork (minus the wear pads) it is made from steel. The pin engages in a socket that the clutch lever moves on a shift rod.

Here is a pic of the old fork’s fit on the shift sleeve

Note the poor fit compared to the new one below


The wear pads will go in the black shaded area of the fork. This is to ensure that axial shifting force is through the center of the shift sleeve like so.


Compare that to the old arrangement. See below


So the only question for me right now is how am i going to make/attach the wear pads:
a) I am going to experiment with SiBronze brazed right onto the fingers. Build up enough to be able to machine them to size.
b) Make little pads of bronze stock on hand and silver solder them to the fingers.

I’ll make samples of each from scrap and then decide.

 

[RobinHood]

Keep posting on the 3D metal printing of this part boys that’s pretty interesting. View of the future.

If you guys do finish a cad model I could print a sample for fitment. I just need the .stl file.

Will do John. Thanks for the offer. I have been “designing on the fly” in order to make this thing work.

 

[RobinHood]

$78 bucks for a custom handle printed in metal. Wow. And Tom said it would take him a day to make. So saying $75/hr for machining * 8 hours = $600 part.

I was thinking the same thing. It is sure impressive what can be done nowadays. Time for me to get a better computer that can run a 3D CAD program.....

 

[PeterT]

I think you got it. Just figure out the soldering & home free. What some guys do is make a few center punch pip marks distributed on the base surface. These provide a small gap for solder to flow into & fill. Now you can clamp the bronze into position with low heat draw cheapo alligator clips, it stands on the pips & stays put. Pre-flux surfaces, lay the solder wire around the perimeter. Then all you have to do is work the torch to apply even heat & the solder is drawn into the gap. And then you have one free hand to video & show us how it went LOL

So is this extended fork blade now negating the sketch in your post#6 that has the end cap kind of like the bottom end of an engine connecting rod? Or does it have to circumnavigate the shaft & be clamped at the split line with those bolts

 

[RobinHood]

So is this extended fork blade now negating the sketch in your post#6 that has the end cap kind of like the bottom end of an engine connecting rod? Or does it have to circumnavigate the shaft & be clamped at the split line with those bolts

Yes it does. It was an idea i had to stabilize the fork in the shift sleeve. But after doing more research and talking with @turner at the tool demo, i concluded that my design would not gain anything other than complicate the part unnecessarily. When 500+ hp engines are shifted at 7000 rpm with cutch forks whose wear pads are “running dry” that are not much bigger than what i have in the Colchester, i think what we have now is plenty strong enough.

Thanks for the tip about soldering; i will experiment with it.

 

[PeterT]

I was thinking the same thing. It is sure impressive what can be done nowadays. Time for me to get a better computer that can run a 3D CAD program.....

After seeing oxtool video I think I might be trying this sooner than later. This has been in the back of my mind all along. My radial engine has some funky 3d multi bend induction tubes from the manifold up to the heads. I have just been messing around test bending 5/16" dia copper alloy brake line & aluminum aircraft hydraulic line & the scrap pile is growing. Of course I just bought a hand bender tool but tubing has minimum bend radii before kinking or oblonging so kind of limits the geometry. They also have to have flared ends to seal in the head. Maybe all this could be incorporated into a 3DP. Its not really old world replication but I think I might take a winger just to see. Now... will the exhaust tubes turn to melted turd under temp? The induction tubes will always be cool & are the bigger challenge anyways but I better be 100% sure about geometry. Hmmm...

 

[Johnwa]

$78 bucks for a custom handle printed in metal. Wow. And Tom said it would take him a day to make. So saying $75/hr for machining * 8 hours = $600 part.

I didn’t think it would take 8 hours to do the handle. Then I watched the video, holy crap! He would have taken half the day dialing stuff in. Reaming and then lapping holes, that’s a precision way way beyond where I’m at.

 

[Tom O]

After seeing oxtool video I think I might be trying this sooner than later. This has been in the back of my mind all along. My radial engine has some funky 3d multi bend induction tubes from the manifold up to the heads. I have just been messing around test bending 5/16" dia copper alloy brake line & aluminum aircraft hydraulic line & the scrap pile is growing. Of course I just bought a hand bender tool but tubing has minimum bend radii before kinking or oblonging so kind of limits the geometry. They also have to have flared ends to seal in the head. Maybe all this could be incorporated into a 3DP. Its not really old world replication but I think I might take a winger just to see. Now... will the exhaust tubes turn to melted turd under temp? The induction tubes will always be cool & are the bigger challenge anyways but I better be 100% sure about geometry. Hmmm...

My Dad worked at the dockyard in Victoria and told us of bending pipes filled with rosin so they would not collapse. Another way would be to use ceribend a low heat metal to fill the tube. I have some of either if you want to give it a go.
https://www.rotometals.com/low-melt...MIjc2HuOb13wIVyh6tBh0eggUTEAAYAiAAEgKuffD_BwE

 

[turner]

Yes it does. It was an idea i had to stabilize the fork in the shift sleeve. But after doing more research and talking with @turner at the tool demo, i concluded that my design would not gain anything other than complicate the part unnecessarily. When 500+ hp engines are shifted at 7000 rpm with cutch forks whose wear pads are “running dry” that are not much bigger than what i have in the Colchester, i think what we have now is plenty strong enough.

Thanks for the tip about soldering; i will experiment with it.

Clarification on the automotive shift fork application, they are splash fed...the entire gear box is in a bath, but no pressurized lubrication. New Fork is impressive!

 

[PeterT]

I have some of either if you want to give it a go.

I might just take you up on that. I'll post my progress elsewhere so we dont detract this thread. I also have questions about flaring maybe some of you guys have experience with. So far my bends are ok but that's only because I am using ductile test materials. Most guys use thin wall stainless & apparently that is a butt kicker which can consume a few meters of 'education'.

 

[DPittman]

My Dad worked at the dockyard in Victoria and told us of bending pipes filled with rosin so they would not collapse. Another way would be to use ceribend a low heat metal to fill the tube. I have some of either if you want to give it a go.
https://www.rotometals.com/low-melt...MIjc2HuOb13wIVyh6tBh0eggUTEAAYAiAAEgKuffD_BwE

I've bent small diameter copper and steel tubing for hydraulic systems(low pressure) and found filling the tubes with sand worked surprisingly well.

 

[RobinHood]

Clarification on the automotive shift fork application, they are splash fed...the entire gear box is in a bath, but no pressurized lubrication. New Fork is impressive!

Thanks @turner .
This one is the same: it has a dedicated oil feed from the oil rail above it. I modified the oil feed line so that both FWD, REV, and the shift fork get equal amounts of oil flow. The factory just has 8mm spigots tapped off the main feed tube resulting in the first take-off receiving the most flow and it peters out from there - to the point where there is almost nothing left for the 5th bearing on the input shaft. The equal flow for the three most “stressed” items (clutches and fork) was achieved by making Delrin inserts for the spigots: the first one in line (closest to the supply) was drilled 5mm, the second 6mm and the last one 7mm. This causes a slight head pressure in the supply rail and then equal flow to the components.

 

[RobinHood]

I decided to use SiBronze and braze the pads


Rough macining is done. I still have to clean off the flux and make the pads a bit nicer. There are a few low spots i may touch up. The wear surfaces are about 1.5mm thick before you get to the tool steel. I am hoping good enough for about 30 years or so....