Swing arm link for the Frog and some questions about it

[FC5687 18]

Who has tried it?

https://www.thingiverse.com/thing:6405879

It is funny as the Shaft file looks very different than the one from Japanese website.

https://reccrafters.tech/?p=853

Please see attachment as I spot out one has larger end than the other.

 

[Saito2 7319]

Edit: Sorry I waffled on a bit in the following post. My contribution isn't really pertinent to the question at hand. Please disregard. / Curious to hear any opinions on this set up as well. Historically, I've always bushed the inner pivot point to better support the arm vs punched metal hole in the gearbox sideplates. This was followed shimming the outer pivot cap if need be to prevent binding. Most of the arm binding I've found is actually related to the dogbones. The dogbones have to operate over many extreme angles as the compresses and often develops a tight spot when the dogbone's drivecups are directly across from one another (basically when the distance is the shortest). Removing o-rings from the inside of the drivecups helps but then then you risk tossing the dogbone at full extension.

[Frog Jumper 3813]

Oooo!  That swing arm bearing thingy look neat.

Terry

 

[FC5687 18]

3 hours ago, Saito2 said:

Curious to hear any opinions on this set up as well. Historically, I've always bushed the inner pivot point to better support the arm vs punched metal hole in the gearbox sideplates. This was followed shimming the outer pivot cap if need be to prevent binding. Most of the arm binding I've found is actually related to the dogbones. The dogbones have to operate over many extreme angles as the compresses and often develops a tight spot when the dogbone's drivecups are directly across from one another (basically when the distance is the shortest). Removing o-rings from the inside of the drivecups helps but then then you risk tossing the dogbone at full extension.

I have been using CVD for years. No dogg bone.

[RichieRich 772]

I've noticed that if you put a lot of miles on your frog, the rear arms will develop a rather large amount of slop. This will put extra stress on the dog bones and probably the diff. I can definitely try printing this and see what happens. I believe I have a used set of rear arms somewhere in my junk box. I see there is a requirement for a couple of 50mm shafts. I would have to source those or find a suitable alternative.

[FC5687 18]

1 hour ago, RichieRich said:

I've noticed that if you put a lot of miles on your frog, the rear arms will develop a rather large amount of slop. This will put extra stress on the dog bones and probably the diff. I can definitely try printing this and see what happens. I believe I have a used set of rear arms somewhere in my junk box. I see there is a requirement for a couple of 50mm shafts. I would have to source those or find a suitable alternative.

I am seeking 5x50mm titanium for that 

Regarding the diff, I guess a well made ball diff from MIP might cure the issue.

 

[Kowalski86 4073]

This looks like it would do a better job at keeping dirt out, when I ran my Frog off-road the pivot-tube thing would fill up with dust.

1 hour ago, RichieRich said:

I've noticed that if you put a lot of miles on your frog, the rear arms will develop a rather large amount of slop.

I've found the re-re Frog arms to be slightly more flexible than vintage arms, which probably doesn't help. Good for durability but bad for retaining dogbones.

The metal parts up front get super sloppy too, I had to start using loctite to keep the axle carrier nuts from backing off.

[Kowalski86 4073]

1 minute ago, FC5687 said:

 Regarding the diff, I guess a well made ball diff from MIP might cure the issue.

It will fix the eiff issues, but honestly, if you still have the original diff in your Frog I'd just keep using it and only order a MIP diff once it wears out. The "monster" ORVs need the MIP diff more than anything else.

It took well over 30 years, a faster motor, and who knows what sort of driving to ruin the diff in my Frog.

[RichieRich 772]

My "test" frog has a Robinson Racing ball diff + universal sliders. So, that nonsense can easily be isolated. 

[FC5687 18]

1 hour ago, RichieRich said:

My "test" frog has a Robinson Racing ball diff + universal sliders. So, that nonsense can easily be isolated. 

Mine has Thorp 5400 plus CVD as well. But swing arm link has bearing there and should improve the travelling of the arm.

[Pizza Frog 689]

That looks to be an excellent mod.

If Tamiya ever releases an 'evo' frog then it should have bearings in the swing arm pivot point and thicker gearbox sides.   

When I bought my vintage frog,  I noticed that the MD13 parts were bent inwards slightly, so I tested the frog with normal MD13 parts and it spat out dogbones like crazy.
The bent MD13 parts seem to tighten up the swing arm without causing binding when the dogbones are horizontal but will be tight enough when the arm is at full droop to stop the dogbones coming out.  

[FC5687 18]

1 hour ago, Pizza Frog said:

That looks to be an excellent mod.

If Tamiya ever releases an 'evo' frog then it should have bearings in the swing arm pivot point and thicker gearbox sides.   

When I bought my vintage frog,  I noticed that the MD13 parts were bent inwards slightly, so I tested the frog with normal MD13 parts and it spat out dogbones like crazy.
The bent MD13 parts seem to tighten up the swing arm without causing binding when the dogbones are horizontal but will be tight enough when the arm is at full droop to stop the dogbones coming out.  

My friend is kindly modified the STL files, so I can have it work with the swing arm link. The reinforced arm should be stiffer, especially I will use Nylon 11 CF. 

Blackfoot_Rear_Left_Arm_-_Reinforced FC.stl Blackfoot_Rear_Right_Arm_-_Reinforced FC.stl

[FC5687 18]

6 hours ago, Kowalski86 said:

It will fix the eiff issues, but honestly, if you still have the original diff in your Frog I'd just keep using it and only order a MIP diff once it wears out. The "monster" ORVs need the MIP diff more than anything else.

It took well over 30 years, a faster motor, and who knows what sort of driving to ruin the diff in my Frog.

I have Thorp for years and have the Thorp diff uses in my FAV. I will put MIP in the Frog rebuilt.

[Kowalski86 4073]

8 hours ago, FC5687 said:

Mine has Thorp 5400 plus CVD as well. But swing arm link has bearing there and should improve the travelling of the arm.

If your Frog has a Thorp diff, you should be set for a long time.

[FC5687 18]

1 hour ago, Kowalski86 said:

If your Frog has a Thorp diff, you should be set for a long time.

Back in 1986 and put into storage over a decade. 

[Frog Jumper 3813]

The ball diffs are neat, but IMO you are better off with a tranny brace and the gear diff.  If you want to use dogbones, use Tamiya #50300 cups with Thorp DBs and axles.  IMO...  YMMV...

Terry

 

[Frog Jumper 3813]

4 hours ago, FC5687 said:

My friend is kindly modified the STL files, so I can have it work with the swing arm link. The reinforced arm should be stiffer, especially I will use Nylon 11 CF. 

Blackfoot_Rear_Left_Arm_-_Reinforced FC.stl 215.41 kB · 2 downloads Blackfoot_Rear_Right_Arm_-_Reinforced FC.stl 251.94 kB · 2 downloads

Would you be able to print a set for me???  I can pay for time, materials, S&H, etc.  PM me.

Thanks!

Terry

[FC5687 18]

1 hour ago, Frog Jumper said:

Would you be able to print a set for me???  I can pay for time, materials, S&H, etc.  PM me.

Thanks!

Terry

I located in Hong Kong and maybe far away from where you live.

[El Gecko 1432]

2 hours ago, Frog Jumper said:

The ball diffs are neat, but IMO you are better off with a tranny brace and the gear diff.

I've still never found the need for one of those braces, even with three ORVs kicking around, but I agree that the gear diffs aren't terrible, and sufficient for most driving. My big-wheel ORV destroyed its gear diff because the axle broke on one of the three little bevel gears, but the replacement diff was cheap, came with all the metal gears to replace all at once, and it's been solid ever since. Also, all my ORVs have their plates pressed in slightly to take out as much slop as possible from the gearbox guts. If they get bent and start skipping, I'll just press them back in. No brace necessary.

That big-wheel car also had the frustrating problem of dropping the right dogbone way too easily once I switched to universals from the original hex setup, and there was a lot of binding and severe vibration at full suspension extension. The binding and vibration was cured by adding these little bumpstops to keep the swingarms from extending too far, which also helps keep the driveshafts from reaching too severe of an angle. Using the standard suspension setup according to the manual will result in the driveshafts getting pulled off-center (only at full extension), resulting in more drag on the gearbox, more wear on the driveshafts, and more likelihood of them popping out. The bumpstops keep the driveshafts more inline with the rest of the gearbox, smoothing things out. A lot of the ORV's handling issues are because of the rear end raising up during coasting or deceleration and causing phantom e-braking when the driveshafts bind.

To keep from losing dogbones I joined the two swingarms at the pivot with a simple metal sleeve through both, cut to length and tied together with M3 allthread and nylock nuts. I also added washers in between the swingarms, to keep them more evenly spaced evenly apart. The whole setup was a bit stiff at first on the side-to-side movement, and acted a little like an anti-rollbar keeping the sides more connected, but after some driving it's loosened up and each side moves smoothly and independently. And it really took out a lot of slop from the swingarms. Immediate improvement and I haven't dropped a dogbone since!

IMHO even though they wore out quickly, I feel that Tamiya should have kept the original hex driveshafts instead of switching to dogbones/universals. The originals are much less sensitive to flex and slop in the system.

[RichieRich 772]

On 8/29/2024 at 1:35 AM, FC5687 said:

My friend is kindly modified the STL files, so I can have it work with the swing arm link. The reinforced arm should be stiffer, especially I will use Nylon 11 CF. 

Blackfoot_Rear_Left_Arm_-_Reinforced FC.stl 215.41 kB · 9 downloads Blackfoot_Rear_Right_Arm_-_Reinforced FC.stl 251.94 kB · 12 downloads

I opened these in the Ultimaker Cura slicer and they are huge! What is the appropriate scale/size?