Wear on the driveshaft of my MF01X

[Juggular]

This whole thing made me wonder what's the optimal angle.  Google Ai said 20 degrees, but that seemed too small. 

So I measured it.  You get 22 degrees when the dog bone is all the way in.  It cannot rotate freely. 

When it's about half way in, you get 30 degrees.  

And that's what o-ring does. 

It keeps the dog bone from burying too deep into the cup. (I've had some chassis where 1 o-ring on either end would bind. Hence the bagel cut.) 

If you go too far out, you can bend more, but it could fall off. 

At high angles, the pins could have less contact area. (This is NOT a well-made dog bone, 3Racing!)    

Tamiya knew that MF01X has to work with greater angles.  So Tamiya's dog bones have longer pins (at least on MF01X).  When the suspension droops, the pins' contact area won't shrink.  

(I just discovered that the wheels go in and out like 1mm, shrinking and expanding the distance.  That's a lot of play.  I've got to find a way to reduce that.)

I'd say MF01X's dog bone angle is about 30 degrees. That is right at the very limit of it. More than this, the wear would be severe.  

What's great about CVDs is that they have 2 axis to work with (even though they are not true CVDs).  So their articulation is much greater. (about 40 degrees)

CVD angle and the drive cup angle have to match up.  Otherwise they'll be out of phase.  Which means the 40 degree angle of CVD is limited by the 30 degree drive cup angle. 

But, at least CVDs won't allow the dog bone to go too deep or too shallow (if made in the correct length).  

The conclusion?  The dog bone should have less than 30 degree angle.  

@Ernoman's new shafts' angles look to be about 15 degrees. That's safe. 

I have no idea why I bought this protractor. I feel I had it for at least 10 years.   

But it's Friday night, and I thought I'd use it. What nerdy fun! 

 

[Ernoman]

@Juggular great post 👍 awesome!

I'd rather ride it on the high setting. But when I do the pin barely touches the cup:

On the low setting it looks a lot better:

So, it will remain as such. 

Edit: these shafts are intended for the M5. So the high setting of the MF01x may require longer shafts. That would explain why it does not sit right on the high setting.

[Kowalski86]

4 hours ago, Juggular said:

(I just discovered that the wheels go in and out like 1mm, shrinking and expanding the distance.  That's a lot of play.  I've got to find a way to reduce that.)

Some 5x8x0.5mm teflon washers should take care of the play in your wheels.

@Ernoman  I'm not sure if you've looked into fixing the uneven droop, but a pair of ball connectors from TAM9805825 does the trick by moving the upper linkage forward, and clearing the transmission tunnel.

[Ernoman]

17 minutes ago, Kowalski86 said:

Some 5x8x0.5mm teflon washers should take care of the play in your wheels.

@Ernoman  I'm not sure if you've looked into fixing the uneven droop, but a pair of ball connectors from TAM9805825 does the trick by moving the upper linkage forward, and clearing the transmission tunnel.

On the low setting this is not an issue. When I rode the high setting I just limited the left to the same droop as the right using a sponge under that upper arm. Worked. 

[JimBear]

Just bungling in here ... is the MF-01x less suitable for a "Rally" setup compared to the M-05/M-06? Or are they all as "good" (small rims and tyres, etc)? 

[Juggular]

3 hours ago, JimBear said:

Just bungling in here ... is the MF-01x less suitable for a "Rally" setup compared to the M-05/M-06? Or are they all as "good" (small rims and tyres, etc)? 

MF01X is less refined than M06.  But the AWD and the taller stance makes it an effective rally version of M-chassis.  Nothing like XV01, mind you.  But MF01X can go places where M05 or M06 just can't.  

I wouldn't take my M06 off road unless I almost lock the diff.  Even so, I'd hesitate, because the ride height is so low, and the RWD isn't the most stable thing for a small tail-heavy chassis.  

No such qualms with MF01X.  I've put on a bit larger tires, supple shocks, and really stiff differential grease.  I don't think it can compete with a larger and proper buggies (even RWD buggies).  But if you wanted a VW Baja bug to do rally in a realistic shape (not like the Monster Beetle), MF01X is the way to go. Not M06. 

M06 is quite low. 

Another rear-motor AWD. 

M06 is realistic for VW, in the sense it's got the RWD. But it's not really good off road (even on-road, you need really sticky rear tires). 

One might think, RWD with a rear-overhang motor is good enough to terrify this poor lady.     

But that's because each tire can have few hundred pounds of weight.  RC cars just don't have that kind of weight.  So low-riding M06 when compared to MF01x isn't good off-road.   

Even these fellows would prefer AWD. 

I'm afraid RWD rally cars work in real life only because they've got the massive weight of steel block on the rear tires. 

Generally, I'm a fan of RWD buggies, because RWD is more fun for me. 

But if you wanted a rally version of a much narrower M-chassis, I'd go with AWD.  There isn't a lot of options when it comes to AWD M-chassis, aside from XM01. But XM01 is twice as expensive. It's the same price as XV01.  When the arm length is very limited, I don't know if XM01 would be as effective as XV01. Given that limitation, I'll take the more economical and cruder MF01X. (At least until other members report that XM01 is awesome. Personally, I'd prefer if they had issued something cheap like MF01X with the motor in front.)  

 

[OoALEJOoO]

5 hours ago, JimBear said:

Just bungling in here ... is the MF-01x less suitable for a "Rally" setup compared to the M-05/M-06? Or are they all as "good" (small rims and tyres, etc)? 

A stock MF-01X is definitely better than a M-06 because of its 4WD and increased height as @Juggular has mentioned.

The interesting bit is that using MF-01X uprights on a M-06 to create a rally version, plus adding a gyro to temper the car on gravel, can produce a quite fun M-06Ra. I experimented with this on my project thread:

Tamiya M-06Ra Mazda Miata

Tamiya Rally Car Review

[Juggular]

8 minutes ago, OoALEJOoO said:

MF-01X uprights on a M-06 to create a rally version, plus adding a gyro

Wow, that's impressive!  

It's more interesting that it does better on-road too. Raising it 6mm is quite a bit taller.  Not just the uprights, but getting the right dog bones and even changing to 3mm bearings is quite a job!  I am certainly tempted.  

And gyroscope would definitely help.  

I think one of these for Flysky G7P has a gyro. I haven't tried it yet. But I did get it for M06 which is the king of fishtailing.  I have a feeling that it wouldn't be not as good as a dedicated gyro, though.   

 

[Honza]

Rule of thumb on MF-01X is to not mount the lower arms to the "high" position. You can still get decent ride height by cutting a little part of the arm and using longer dampers, but keeping the arms in the low position makes them parallel to the drive shafts and they won't move as much in and out of the drivecup. The O-rings keep the driveshafts centered properly.

This is how I run mine, driveshafts are at the angle limit, yet after 2 seasons (~10 races, each takes 2 fully charged batteries + some training sessions), the wear is minimal.

Also, I run my driveshafts dry. While it's not ideal for longevity, the grease that come with the kit is even worse. I'm not sure, if something else, like AW grease, would be better or not.

Optionally, you can get TT-02 gearbox joints, they appear to be made from better alloy: https://www.tamiya.com/english/products/54477/index.html

PS: I know that my car is quite different from the stock, but geometry is same and this setup was tested on top mounted upper links - those were mounted in high position.

[alvinlwh]

23 hours ago, Kowalski86 said:

moving the upper linkage forward, and clearing the transmission tunnel.

I did that and it spit the dogbones and CVDs out. Ended up reducing the droop instead. 

[Kowalski86]

21 hours ago, JimBear said:

Just bungling in here ... is the MF-01x less suitable for a "Rally" setup compared to the M-05/M-06? Or are they all as "good" (small rims and tyres, etc)? 

The MF-01X is more suited to rallying than the others, however none of them are really "good" rally chassis in my book. All of them require extensive modifications.

[OoALEJOoO]

4 hours ago, Honza said:

Rule of thumb on MF-01X is to not mount the lower arms to the "high" position. You can still get decent ride height by cutting a little part of the arm and using longer dampers, but keeping the arms in the low position makes them parallel to the drive shafts and they won't move as much in and out of the drivecup. The O-rings keep the driveshafts centered properly.

That is a very good point. Having the dogbone parallel to the arms would result in theoretically having the dogbone remain in the same axial position regardless of suspension movement. However, I suspect that the wear caused by the axial movement is probably much smaller than the wear caused by the dogbone pins inevitably moving relative to the drivecup in-and-out every revolution because of the overall suspension angle. In other words, the pin movement on the slot caused by not being parallel to the suspension happens only during suspension travel, while the pin movement because of the general angle happens each and every time the wheel rotates. Your insight is very relevant since it can only help and making the shocks longer can be as easy as using the longer eyelets.

My thought is that by far the largest contributor to wear is the running medium. Having aggressively abrasive particles between the surfaces is the foremost factor for troublesome tribology . Particles come in all sorts of shapes and hardnesses. If the car is run on fine sharp sand (quartz), wear will happen very quickly. You could do all sorts of things to improve it but unless you remove the medium or go with extremely hard mating parts, wear will still get you sooner rather than later. If the dirt is mostly well-worn clay dust, then wear would be orders of magnitude less.

Regarding material improvements, Tamiya offers 54048 wheel axles in "reinforced" material. Not sure exactly what it means by reinforced, but if the material is harder, it should resist wear better.

Pushing the dogbone pins out, and inserting high-hardness alternatives could also improve reliability. Not sure any of this is worthwhile though, as it might be cheaper & easier to just replace standard parts.

19 hours ago, Juggular said:

It's more interesting that it does better on-road too. Raising it 6mm is quite a bit taller.  Not just the uprights, but getting the right dog bones and even changing to 3mm bearings is quite a job!  I am certainly tempted. 

Finding MF-01X uprights 19000815 is an option, or also M-05Ra uprights 51425. They are both identical except for color: MF-01X are red, while M-05Ra are black. If you decide to pull the trigger, it would be great to see your creation .

[Ernoman]

I suspect dust getting into the grease has been the problem. I knew that was bad. I just did not expect it to be this bad.

My car is fixed and I'm running it on the low setting in the back. The front is still at the high setting and for a beetle that actually looks correct. 

@Juggular what wheels did you fit and would they fit now I'm running the lower ground clearance at the back?

[Juggular]

11 hours ago, Honza said:

Rule of thumb on MF-01X is to not mount the lower arms to the "high" position. You can still get decent ride height by cutting a little part of the arm and using longer dampers, but keeping the arms in the low position makes them parallel to the drive shafts and they won't move as much in and out of the drivecup. The O-rings keep the driveshafts centered properly.

This is how I run mine, driveshafts are at the angle limit, yet after 2 seasons (~10 races, each takes 2 fully charged batteries + some training sessions), the wear is minimal.

Also, I run my driveshafts dry. While it's not ideal for longevity, the grease that come with the kit is even worse. I'm not sure, if something else, like AW grease, would be better or not.

Optionally, you can get TT-02 gearbox joints, they appear to be made from better alloy: https://www.tamiya.com/english/products/54477/index.html

PS: I know that my car is quite different from the stock, but geometry is same and this setup was tested on top mounted upper links - those were mounted in high position.

WHOA!!! That makes a lot of sense. 

Ideally, the shaft and the arms should be parallel.  Otherwise, the shaft would have to move in and out.  That's why there is bump steer (if it's steering linkages).  

I'll have to see if that could be done easily by using longer boots on the shocks, etc.  

 

[Juggular]

1 hour ago, Ernoman said:

I suspect dust getting into the grease has been the problem. I knew that was bad. I just did not expect it to be this bad.

My car is fixed and I'm running it on the low setting in the back. The front is still at the high setting and for a beetle that actually looks correct. 

@Juggular what wheels did you fit and would they fit now I'm running the lower ground clearance at the back?

They are Traxxas SCT tires. (7674x wheels + tires). 

I'm a cheap guy. I almost never spend $30 for a set of wheels and tires.  But I thought the stock Tamiya tires were too low-rider.  Baja buggies mount oversized tires.

So I went for slightly larger tires.  

https://www.amazon.com/dp/B07ZDLDB44?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2

The treads are not as aggressive, and they are a bit slippery.  

 

[chris.alex]

After building my MF01X, I experimented with different ride height settings. For me, the best solution is a mix of high (upper arms) and low (lower arms) ride heights, combined with touring car wheels. Since the only problem I ever had with the MF01X was the rear shafts falling out, I installed universals (GPM) early on. 

I agree with others that it is rather a good on-road car than a rally car. I really like my MF01X and for a while it was my most driven car. I am running a 10.5t motor with a 20t pinion and TL01 speed gear. The car drives well and is easy to control. 

[Ernoman]

Thanks, I found them at about 18 euros for two of them. Still hurts when my car eats them in two rides. Maybe they will last longer once all the problems of the suspension are corrected.

[Ernoman]

Took the car for a spin. The ride height is a bit too low in the back. I could make the suspension another notch stiffer. But I could also increase the height of the shocks. This is how it would sit when I do:

I'm unsure if this is acceptable. The pin only just touches the cup. Would this setting work out would it just wear out the drivetrain again?

[Juggular]

Ah, that pin is as short as my 3Racing one.  I'd feel uncomfortable with that myself.  

But there are conditions where it could work.  1) the ball on the dog bone is snug in the cup. Meaning, the ball isn't rattling on the inside of the cup. 2) if that is as far down as it goes. You should pull down a little to see if it does. 3) the dog bone does not move sideways (since yours is a CV joint, you could use shim to make sure it goes in as much as it could).  

The 3D crowd would recognize 1) 2) 3) are basically x, y, z plane.  With good lube it may last a bit.  

I am thinking to replace my cv joint with something better.  

 

[OoALEJOoO]

@Ernoman An alternative to get more pin engagement is using shims to move the diff cups out toward the dogbone by placing the shims on the cup's shaft.

I don't have my MF-01X accessible right now, so maybe someone could confirm if regular 5mm shims, Tamiya 53587 or generic, would allow having shims placed on the diff cup without rubbing against part F7. Shimming would mean the flat profile of the cup would engage a bit less with the diff slot, but given you don't have crazy motor power, it should hold without issues.

[Ernoman]

19 hours ago, OoALEJOoO said:

@Ernoman An alternative to get more pin engagement is using shims to move the diff cups out toward the dogbone by placing the shims on the cup's shaft.

I don't have my MF-01X accessible right now, so maybe someone could confirm if regular 5mm shims, Tamiya 53587 or generic, would allow having shims placed on the diff cup without rubbing against part F7. Shimming would mean the flat profile of the cup would engage a bit less with the diff slot, but given you don't have crazy motor power, it should hold without issues.

Thanks for the tip. That works a treat

Nevermind the dust on the cup. I still need to do some cleaning. The scratced are from the **** thing not wanting to come out. I had to take the whole car apart to push it out from the inside.

She is now on the low setting with longer shocks. Shims behind the cup and a spring in the cup. This is the ride height I need. 

Thanks for all the tips.