Sealed gear diffs

[BuggyDad]

One thing that bugs me particularly about my DT-03 and Blitzer-based Falcon is their unsealed gear diffs (although there is the option of a ball diff in the case of the DT). If I get on with my BBX ball diff I probably will try the DT-03 one and maybe it'll be fine. But, I am wondering a little, with the power of 3d printing, whether there night be another solution I could cobble together. Both these chassis mount suspension direct to gearbox casing but I've already bodged reinforced suspension mounting to both. 

Each of these is a bit unlikely I suppose, but you never know. 

One possibility is if I could find a diff that takes the same style of outdrives (so 1150 gearbox bearings, basically) and has same or smaller diameter and same or smaller axle length, perhaps I could 3d print a new gear (spur and the little one, whatever that's called) to fit that in. I guess unlikely but if that were possible it could be just one part to model and spacers etc to fit. May not have to be 0.6 mod, just an acceptable diameter. It also strikes me it'd most likely be a bit smaller and therefore up the gearing, which the car could do with (up to a point). 

I note the TA06 ball or sealed gear diffs are also used in M-07&8, XV-01, TD2&4, BBX, probably more besides. Nice to see a part get such wide use. They take the big bearings though so big change to gearbox housing, alongside all the other changes, to use one. 

Another option is to model the necessary interface parts to fit another existing gearbox to the car. Kind of feels doable but it'd cross way over the line of "just get a different car". If I was looking into this I'd look at the BBX gearbox first (similar layout, 4 screw holes at the base and a forward brace, takes a common diff and a slipper). 

A final thing to consider is whether the DT ball diff would fit in the Blitzer. It takes same style of out drives and I read it's a smaller diameter, so maybe I could model a new spur gear for the Blitzer to take that. My buggy wheel sized Blitzer in particular needs the gearing increased and if they're both the same modulus then axle to axle distance between two gears is proportional to total tooth count, so with the right tooth count on the baby spur, in theory they would mesh perfectly, so long as nothing else in the gearbox is in the way (probably would be though, since I'd have to increase the size of that gear).

Just chucking this out there, it's not thought through - more just thinking out loud on a subject that's a bit too niche to find much on. 

[Wooders28]

8 hours ago, BuggyDad said:

One thing that bugs me particularly about my DT-03 and Blitzer-based Falcon is their unsealed gear diffs

Are you meaning , sealed enough to hold oil? As the DT03 diff is kind of sealed (compared to say, the hornet/lunchbox).

You want to alter the diff viscosity, like on modern race cars?

I've fitted an O ring, behind a bevel gear, before screwing it together, which has stiffened it up a bit, also tried bluetac (and filled with superglue for the speedrun car..) .

The gear bag is only a fiver, so not too much heart ache, if things don't work.

[TurnipJF]

Is the diff plastic thick enough for you to machine grooves for o-rings to seal the outdrives? If you do this, and seal up the lid with gasket maker, it should hold oil, no?

[BuggyDad]

2 hours ago, Wooders28 said:

Are you meaning , sealed enough to hold oil? As the DT03 diff is kind of sealed (compared to say, the hornet/lunchbox).

You want to alter the diff viscosity, like on modern race cars?

I've fitted an O ring, behind a bevel gear, before screwing it together, which has stiffened it up a bit, also tried bluetac (and filled with superglue for the speedrun car..) .

The gear bag is only a fiver, so not too much heart ache, if things don't work.

Yeah I guess I mainly just mean I think it's a shame they don't dimension lower end gearboxes to take already in production diffs that can be adjusted. Or at least, I'm interested in finding a better solution. I know there's thick grease and blu-tak etc but my attempts that way have tended to occupy the extremes of adjustment too much, and change over time. Seems to me that to stiffen up a diff from fully open makes a big difference to how a car drives in a way that's of real benefit even if you're not racing. You don't need precision but I reckon for us a bit of modest limited slip is much better than fully open or really jammed up. 

That and I've always got some idea buzzing round my head for the next mod. 

1 hour ago, TurnipJF said:

Is the diff plastic thick enough for you to machine grooves for o-rings to seal the outdrives? If you do this, and seal up the lid with gasket maker, it should hold oil, no?

It might be. O-ring groove is an interesting idea. Will look. Although it would need a lathe and the ability to use it, counter-intuitively perhaps more difficult to achieve than designing a new gear component or two. I already have the gasket compound sealing my DT-03 one and 500k oil in it, but that's only so thick to try to avoid it leaking. 

[ThunderDragonCy]

I have had a think about this too, but it's very tricky with the outdrive/bearing limitations. I did try getting a gear printed a few years ago but the resolution wasn't anywhere near good enough. You could probably do it now with polished sls, but tolerances are still a bit slack for gears IMO. 

 

[BuggyDad]

18 minutes ago, ThunderDragonCy said:

I have had a think about this too, but it's very tricky with the outdrive/bearing limitations. I did try getting a gear printed a few years ago but the resolution wasn't anywhere near good enough. You could probably do it now with polished sls, but tolerances are still a bit slack for gears IMO. 

Interesting on the resolution/tolerances. I'm just ordering some polished MJF so it'll be interesting to see what that's like when it arrives. I think I've only had natural finishes before. I believe MJF and SLS are same strength in the x/y axis but MJF retains that strength in the z, which is why I've gone for it. Does SLS have other advantages? They're pretty much the same money. 

[Collin]

Doing around with 3D prints since many years now and since I am working on a 10pcs kit I need all parts ten times equal. Since this experience I can say 3D print, even MJF and SLS is always a shot into the dark. Even within the same printjob I have tolerances +/- 2/10mm which is A LOT if you want to have things running fine, e.g. gears, bearing seats, axial play...

Then once you modified your 3d model to the printer, they callibrate it new or tweak their setting and everything starts from the begin.

[ThunderDragonCy]

52 minutes ago, BuggyDad said:

Interesting on the resolution/tolerances. I'm just ordering some polished MJF so it'll be interesting to see what that's like when it arrives. I think I've only had natural finishes before. I believe MJF and SLS are same strength in the x/y axis but MJF retains that strength in the z, which is why I've gone for it. Does SLS have other advantages? They're pretty much the same money. 

SLS/MJF are kind of interchangeable in my mind. The tolerance is +/- 0.1 which isn't really enough.

[Honza]

would this work? DT-03 has quite similar differential to TA01, if this kit fits into the gear, I don't see any obstacle other than need to drill 10mm holes for drive cups.

[Wooders28]

1 hour ago, BuggyDad said:

That and I've always got some idea buzzing round my head for the next mod. 

Mmm, wondering if it's worth sizing up a cheap diff (ie not the Xray active diff!! 😳, Maybe Dirt Master? Although, a quick tally up, looking to be around the £40 mark for all the parts, so may aswell go with the ball diff...) and 3d printing / manufacturing a counter gear, to suit that pitch?

With enough interest, we managed to get a company to make a hardened main shaft gear for the DF03 (when the helicopter pinion supply dried up), not sure what costs would be involved in that, to make it viable....🤔

https://www.rwracing.co.uk/product/tamiya-df-03-main-shaft-gear-6-module-18t-12mm-wide

[BuggyDad]

Thought it worth updating this thread since the talented @wtcc5 and @Quincy have solved this little problem. See here:

 

Chuckle.

So at some point I shall have a go at exactly this mod on my DT-03, but it can await future orders from PJ and modelsport. 

[Honza]

@BuggyDad thanks for notice that the video doesn't work anymore. It's from this channel, that also posted interesting video with hopped up TA01