Kingcab/madcap diff research

[Misterp180 257]

I am all over this! Currently starting a Madcap rebuild project for the channel and will be super interested in anything that helps resolve the issues I am likely to find during the rebuild 😁

@Kol__ thanks for the tip dude!

[kontemax 1725]

6 hours ago, Kol__ said:

Nice work @Muso31, looks like a solid start. @kontemax, you did something similar to this didn't you? Bolting a centre onto the spur gear with 3 bolts? I'm sure I read some stuff by you on that a while ago.

I did it but I simply replaced the external teeth of the spur gear with a Delrin 48P module, for my Avante 2001 and a 48P module for my Astute.
You can see my modifications here: https://www.tamiyaclub.com/showroom_model.asp?cid=38252&id=24

And here: https://www.tamiyaclub.com/showroom_model.asp?cid=38250&id=24

Keep in mind that these are fixed couplings. The Super Astute then has its own slippery clutch.

I wonder if this sort of design could provide mounting for both a standard gear and also a slipper clutch? By bolting either into the centre of the spur gear, giving the user the option for both. Perhaps something like the DF-03 slipper clutch, which is widely available still I think, could be re-worked into this design?

The problem of the slippery clutch for the Astute gearbox is that the gearboxes are different.

Max
 

 

[kontemax 1725]

10 hours ago, Muso31 said:

 

Hopefully something along these lines is going to be a significant improvement, although ultimately I'd have thought a slipper clutch design is required. @kontemax is this in line with what you were thinking?

This is a fixed coupling.
This is what I was thinking about.
The steel gear could have the allocations for both the ball bearings and some holes to reduce the rotating mass.
The plate of the smaller gear can be thinner cause the steel is so hard that is enough, ihmo, and the force applied is radial, not axial.
It could be 1 mm thick in my opinion.

What I can suggest is to make some flexible coupling in the steel plate. Please let me explain (sorry for my bad English):
Posts diameter, in the big gear (for example) 5 mm
Holes diameter, in the steel plate (for example) 9 mm
O-rings squeezed between the two diameters.
You have a radial soft flexible coupling.
This is only one idea.

You can also have a flexible axial coupling.
Smaller steel gear with 1 mm plate, then a pad, then the Delrin big gear, then another pad, then another steel plate.
Everything squeezed together to have a sort slippery clutch.

Max

[Muso31 122]

20 hours ago, kontemax said:

This is a fixed coupling.
This is what I was thinking about.
The steel gear could have the allocations for both the ball bearings and some holes to reduce the rotating mass.
The plate of the smaller gear can be thinner cause the steel is so hard that is enough, ihmo, and the force applied is radial, not axial.
It could be 1 mm thick in my opinion.

What I can suggest is to make some flexible coupling in the steel plate. Please let me explain (sorry for my bad English):
Posts diameter, in the big gear (for example) 5 mm
Holes diameter, in the steel plate (for example) 9 mm
O-rings squeezed between the two diameters.
You have a radial soft flexible coupling.
This is only one idea.

You can also have a flexible axial coupling.
Smaller steel gear with 1 mm plate, then a pad, then the Delrin big gear, then another pad, then another steel plate.
Everything squeezed together to have a sort slippery clutch.

Max

Yep great stuff thanks. I'll make the metal insert a skeleton gear to shed some mass. The spur is on the backburner at the moment whilst I finish the diff, after that I'll have some questions, do you want me to post those here or DM?

 

Just a quick update on the diff and a quick question for all. So far we're looking good...

 

But I now need a drawing to make sure that the seating for the planetary gears is an exact match to the super astute/avante diff. I downloaded an SA user manual so I could screen grab the drawing but as you can see the resolution is poor:

 

 

Can anybody send me a high res version of this or a scan from a manual? Ideally the diff drawing and the diff cap drawing. I need to overlay this drawing in the software to make sure the holes are in the exact same position.  RC community to the rescue?! Team effort haha. 

Thanks all

 

...edit the housings are all modelled now, will get those milled and released in a few weeks time 

[Kol__ 3377]

3 hours ago, Muso31 said:

The spur is on the backburner at the moment whilst I finish the diff, after that I'll have some questions, do you want me to post those here or DM?

It would be cool if questions are put on this thread, for the interest of all, and the record of this work👍😎

Here's hi-res photos of the diff gear mate -

[Kol__ 3377]

This is interesting, looks like it fixes to the gear shaft in the same way as the DF-03, with a 10mm pin (like the axle pins for hexes) -

https://www.ebay.co.uk/itm/394389008298?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=i_yyl0n6qxa&sssrc=2349624&ssuid=tZpl78SaSly&var=&widget_ver=artemis&media=EMAIL

Also, is it a better option to change the pitch of the spur gear whilst this is being redesigned? Is the standard Madcap 0.6 module still the best option here, or would something like a 48 pitch give more options for pinions?

[kontemax 1725]

4 hours ago, Muso31 said:

do you want me to post those here or DM?

If you want please post it here so everybody can read, if not feel free to DM me.

Keep in mind that Avante/Egress diff gear seems to match with the Astute one but no, it doesn't.
Avante/Egress diff gear on the Astute train will break the diff teeth.

Astute has 1 mm teeth module
Super Astute has 05 mm module so both diff gears don't fit each other.
Super Astute has gear diff, if you use it on the Astute without a slippery clutch you will break badly something somewhere.

Max
 

[Muso31 122]

2 hours ago, Kol__ said:

It would be cool if questions are put on this thread, for the interest of all, and the record of this work👍😎

Here's hi-res photos of the diff gear mate -

Yep can keep the questions here, just didn't want to spam people with technical info, but good with me if there's an interest in that anyway.

Thanks for the photos these are perfect. I'm able to overlay them as a guide so I'll get the gear holes/seating added in the right places.

1 hour ago, Kol__ said:

This is interesting, looks like it fixes to the gear shaft in the same way as the DF-03, with a 10mm pin (like the axle pins for hexes) -

https://www.ebay.co.uk/itm/394389008298?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=i_yyl0n6qxa&sssrc=2349624&ssuid=tZpl78SaSly&var=&widget_ver=artemis&media=EMAIL

Also, is it a better option to change the pitch of the spur gear whilst this is being redesigned? Is the standard Madcap 0.6 module still the best option here, or would something like a 48 pitch give more options for pinions?

It's good to be weighing up options regarding the spur design as I'll move on to that once this diff is done (won't be too long). It could be good to have a spur that matches the current vintage set ups, then create one that uses a different/better configuration. Swappable or configurable parts is an option also.

 

1 hour ago, kontemax said:

Keep in mind that Avante/Egress diff gear seems to match with the Astute one but no, it doesn't.
Avante/Egress diff gear on the Astute train will break the diff teeth.

Astute has 1 mm teeth module
Super Astute has 05 mm module so both diff gears don't fit each other.
Super Astute has gear diff, if you use it on the Astute without a slippery clutch you will break badly something somewhere.

The pitch diameter and teeth etc are different, but I'm making an assumption that the planetary gears utilise the same distances/spacing as it's the same gears so they'll need the same mesh. It could be good if someone posts the drawing from an Avante so I can triple check this. Obviously I'll be making these gears fit nicely into a .08 module madcap diff, hopefully there's no surprises here and the planetary gear setup is consistent across all models. 

Just to get sidetracked - I'm a little surprised that people have used the Avante diff in the likes of the kingcab/madcap as it's 1mm smaller in diameter and one less tooth which must make the mesh horrendous. It's being sold as a solution to the ball diff but this is going to cause obvious issues. Anybody who's done this should probably remove it, and I can see from the forums a few people have.

Anyway - yes this spur is going to need some sort of slipper function as I'm assuming the planetary gear diff cannot slip, unless I'm mistaken? So I'd have thought planetary gears must always be used in conjunction with a clutch on the spur

 

[Kol__ 3377]

2 hours ago, kontemax said:

Super Astute has gear diff, if you use it on the Astute without a slippery clutch you will break badly something somewhere.

 

47 minutes ago, Muso31 said:

Anyway - yes this spur is going to need some sort of slipper function as I'm assuming the planetary gear diff cannot slip, unless I'm mistaken? So I'd have thought planetary gears must always be used in conjunction with a clutch on the spur

Ah yeah, I hadn't thought of that, so without something that will slip, like the original ball diff, if replacing with the planetary gears where no slip is possible then it must be used with a slipper clutch or something in the gear train will break. I get ya, so this redesign will have to incorporate a slipper clutch of some sort.

Like @kontemax says though, the gear box is different where the spur gear mounts. The Super Astute gearbox has a little insert that you push into it to hold the slipper clutch shaft. And irrc there is a hole that need to be a bit bigger on the Astute gearbox, but that could be drilled out I believe.

Anyway so does the above constitute at full on requirement for a slipper clutch and therefore a redesigned gearbox housing to support it? If so, is the TD4 slipper clutch a potentially viable candidate for using here? The set up looks like this -

It looks a bit long, but I wonder could it be reworked or only some parts used to make it work in the Astute gearbox housing with some modified custom parts?

47 minutes ago, Muso31 said:

Just to get sidetracked - I'm a little surprised that people have used the Avante diff in the likes of the kingcab/madcap as it's 1mm smaller in diameter and one less tooth which must make the mesh horrendous. It's being sold as a solution to the ball diff but this is going to cause obvious issues. Anybody who's done this should probably remove it, and I can see from the forums a few people have.

Yeah, **** knows what's up with that or how anyone thinks that is a viable option🤷🏻 1 less tooth surely translates to a smaller diameter like you say, so sounds like a disaster waiting to happen if that diff is used in the Astute/Madcap gearbox.

[Muso31 122]

13 hours ago, Kol__ said:

Ah yeah, I hadn't thought of that, so without something that will slip, like the original ball diff, if replacing with the planetary gears where no slip is possible then it must be used with a slipper clutch or something in the gear train will break. I get ya, so this redesign will have to incorporate a slipper clutch of some sort.

I suspect so. So a solution will be needed for the spur. It'd be nice to come up with something that doesn't require a new gearbox cover, failing that theres always the SA cover option. We might need to think about either a none adjustable slipper spur, or something else. This part will need a bit of thought soon.

New diff is done (apart from the cover). Here we have it...

 

 

Sadly Tamiya parts are injection moulded rather than CNC so I'll need to speak to some contacts about manufacturing options, this one isn't as straightforward as the machined alloy components (such as the new diff housing)

[bavee 1032]

19 hours ago, Muso31 said:

Just to get sidetracked - I'm a little surprised that people have used the Avante diff in the likes of the kingcab/madcap as it's 1mm smaller in diameter and one less tooth which must make the mesh horrendous. It's being sold as a solution to the ball diff but this is going to cause obvious issues. Anybody who's done this should probably remove it, and I can see from the forums a few people .

 

18 hours ago, Kol__ said:

Yeah, **** knows what's up with that or how anyone thinks that is a viable option🤷🏻 1 less tooth surely translates to a smaller diameter like you say, so sounds like a disaster waiting to happen if that diff is used in the Astute/Madcap gearbox.

I don't understand why it works either. But hey, it does. Car moves great in a straight line, corners well and doesn't make any strange noise. So...

Maybe it will eat some gears in the long run. But I have some spares so that isn't a problem. At least I can run the car now.

@Sgt.Speirs solution is a great solution, thank you for your effort,  but it is expensive. I still haven't made up my mind about spending that kind of money on the car.

When the new machined diff housings are available I think I will give them a try. I have some spare internals laying around...

[Kol__ 3377]

3 minutes ago, bavee said:

I don't understand why it works either. But hey, it does. Car moves great in a straight line, corners well and doesn't make any strange noise. So...

Maybe it will eat some gears in the long run. But I have some spares so that isn't a problem. At least I can run the car now.

Hey @bavee buddy, sorry that wasn't a dig at you. Just seems like it will wear quickly, keep us updated mate.

 

[Muso31 122]

4 minutes ago, Kol__ said:

Hey @bavee buddy, sorry that wasn't a dig at you. Just seems like it will wear quickly, keep us updated mate.

 

Same I wasn't even aware you were using it - Agreed that it'll cause wear in the long run, at least we'll have some other options in the near future.

10 minutes ago, bavee said:

When the new machined diff housings are available I think I will give them a try. I have some spare internals laying around...

You'll be getting a free set for your input

[Kol__ 3377]

2 hours ago, Muso31 said:

New diff is done (apart from the cover). Here we have it...

 

That looks awesome mate. It is a complicated form isn't it!

[bavee 1032]

No offense taken @Kol__ and @Muso31! I must agree it seems stupid .

Will be summer before I run the car again I think @Kol__. Hopefully with a better solution than I have installed now.

Thank you for offer. But when I choose to use your parts I'll rather pay you for your effort @Muso31.

[bavee 1032]

Thinking about it. Maybe it just works because, as we all know, most Tamiya parts have some "slop" in them and thus the tolerance isn't such a big thing as we think it is?

This or I will find my gears destroyed when I open up the gearbox. 

[Sgt.Speirs 1253]

11 hours ago, bavee said:

 @Sgt.Speirs solution is a great solution, thank you for your effort,  but it is expensive. I still haven't made up my mind about spending that kind of money on the car.

When the new machined diff housings are available I think I will give them a try. I have some spare internals laying around...

Expensive, but solves all the weakpoints which @kontemax mentioned

But when I see all these design proposals here and new gear parts, I‘m not sure that my solution is at the end more expensive.

But I‘m excited how this thread/solution ends

[kontemax 1725]

23 hours ago, Muso31 said:

Just to get sidetracked - I'm a little surprised that people have used the Avante diff in the likes of the kingcab/madcap as it's 1mm smaller in diameter and one less tooth which must make the mesh horrendous. It's being sold as a solution to the ball diff but this is going to cause obvious issues. Anybody who's done this should probably remove it, and I can see from the forums a few people have.

Anyway - yes this spur is going to need some sort of slipper function as I'm assuming the planetary gear diff cannot slip, unless I'm mistaken? So I'd have thought planetary gears must always be used in conjunction with a clutch on the spur

 

I did it and I broke in few seconds one tooth of the diff gear.

Max

[kontemax 1725]

6 hours ago, Muso31 said:

I suspect so. So a solution will be needed for the spur. It'd be nice to come up with something that doesn't require a new gearbox cover, failing that theres always the SA cover option. We might need to think about either a none adjustable slipper spur, or something else. This part will need a bit of thought soon.

New diff is done (apart from the cover). Here we have it...

 

 

Sadly Tamiya parts are injection moulded rather than CNC so I'll need to speak to some contacts about manufacturing options, this one isn't as straightforward as the machined alloy components (such as the new diff housing)

Keep in mind that if you use a gear diff you will lose traction every time you meet some dust and the model will be badly oversteering.

Max

[Muso31 122]

13 hours ago, kontemax said:

Keep in mind that if you use a gear diff you will lose traction every time you meet some dust and the model will be badly oversteering.

Gotcha, it's the first step towards handling more modern motors, maybe some other options on the way in future. I imagine most people will stick to the original ball diff and use the updated housings, but it's nice to have options.

So with the gear diff and ball diff housing complete it's time to finally tackle the spur.  @kontemax any chance you could do some rough sketches regarding your thoughts below? I think I understand what you're suggesting, but for confirmation it could be best to see it on paper. 

On 12/20/2022 at 9:18 PM, kontemax said:

What I can suggest is to make some flexible coupling in the steel plate. Please let me explain (sorry for my bad English):
Posts diameter, in the big gear (for example) 5 mm
Holes diameter, in the steel plate (for example) 9 mm
O-rings squeezed between the two diameters.
You have a radial soft flexible coupling.
This is only one idea.

You can also have a flexible axial coupling.
Smaller steel gear with 1 mm plate, then a pad, then the Delrin big gear, then another pad, then another steel plate.
Everything squeezed together to have a sort slippery clutch.

 

 

On 12/22/2022 at 12:01 AM, Kol__ said:

Anyway so does the above constitute at full on requirement for a slipper clutch and therefore a redesigned gearbox housing to support it? If so, is the TD4 slipper clutch a potentially viable candidate for using here? The set up looks like this

All options are on the table here, personally I'd like to try and keep the stock gearbox housing. It could be good to come up with a design that requires the Asute housing, and a compromise/hybrid that can work in the current setup? 

[Muso31 122]

...Quick favour to ask from all kingcab/Madcap users. Could you please get a set of calipers on the diff and tell me the outer diameter, ideally to 2 decimal places? Mine is 26.15mm but I want to see if there's much fluctuation due to wear etc. 

23 hours ago, bavee said:

Thinking about it. Maybe it just works because, as we all know, most Tamiya parts have some "slop" in them and thus the tolerance isn't such a big thing as we think it is?

I'm making some tweaks to the diff to make the tolerance tighter than whats acceptable at Tamiya, there's quite a bit of end play on the inner gears. Weirdly, the center planetary gear is 0.59 module and the outer are 0.6. Not sure why they didn't make the inner gear 0.15mm bigger to equal 0.6, or make the outer gears 0.59 module also for consistency - although it's close enough and I suppose it isn't as important in a diff as the internal gears don't spin at any great rate.

It's probably these little details though that make them a cheaper manufacturer/product than others. I assume more expensive RC kits are precision engineered, though this is only an assumption 

[kontemax 1725]

13 hours ago, Muso31 said:

So with the gear diff and ball diff housing complete it's time to finally tackle the spur.  @kontemax any chance you could do some rough sketches regarding your thoughts below? I think I understand what you're suggesting, but for confirmation it could be best to see it on paper. 

I'll try to do it tomorrow.

Max

[bavee 1032]

22 hours ago, Muso31 said:

...Quick favour to ask from all kingcab/Madcap users. Could you please get a set of calipers on the diff and tell me the outer diameter, ideally to 2 decimal places? Mine is 26.15mm but I want to see if there's much fluctuation due to wear etc.

26.10 for my used one.

[Kol__ 3377]

On 12/23/2022 at 12:53 PM, Muso31 said:

All options are on the table here, personally I'd like to try and keep the stock gearbox housing. It could be good to come up with a design that requires the Asute housing, and a compromise/hybrid that can work in the current setup?

Definitely bud, would be great to be able to use the existing gearbox case👍🏻🙂 It all hinges around how the spur gear/slipper gear would be mounted. On the Astute/Madcap case it's that shaft held in place by an M3 machine screw. However, the Super Astute slipper (both 1991 and 2018 versions) uses that additional piece in the gearbox and the shaft that goes right through it and is secured with an e-clip. Perhaps some sort of hybrid approach could be adopted. You've got to wonder though, Tamiya made this adaptation already, and in 2018 with modern parts, so they must've done it the way they did for a reason.

[Kol__ 3377]

Brand new one (for my Monster Racer build) is 26.15mm as well.