Shrinking shafts?

[Juggular]

Why are motor shafts getting shorter?  

I noticed that DT04's pinion is barely biting onto the shaft of Torque Tuned.  Why is it so short?  I shimmed the spur gear, so it would not move much.  

I thought I got a short shaft 550, but what I got was long.

I had to cut the dang thing down to 10mm.  I think I'll try a 550 motor on my CC-01.  

After cutting the shaft of 550 and putting away the rotary tool, I noticed that a Brushless motor came with a long shaft too.  Probably 16mm again (1/2 inch).  

It feels like Tamiya's shafts are getting shorter while the other motor's shafts are getting longer.  This shaft won't be covered by the gear cover on DT-04 or DT-03.  It will have to be cut.  What is going on here? 

Does anybody know why Tamiya's shafts are shriveling?  It used to be all about 10 or 11mm long.  But new Tamiya motors seem much shorter like 8mm.  Yet, some motors come with 16mm shafts.  Is it other makers who demand longer shafts?  

---Since I'm venting.... 

Why is Tamiya still giving us pinions made out of cheesium?   

These were $1.40 a piece, shipping included.  Which means the production cost was probably like 50 cents or less. (These are 0.6 module, I'm waiting for a shipment of 0.8m pinions.)

I think these yellowy aluminum/copper alloy is 2000 series? (I assume Tamiya's pure aluminum --er, cheesium-- pinion is 1000 series).  The tensile strength of 2000 series should be at least twice as strong (it's funny how aluminum is weak, so is copper. But together they are stronger).  Steel will last forever. But for the most part, these 2000 series are strong enough (unless you want to run a 6000KV motor on 3S).  Why couldn't Tamiya include these?  These are not expensive.  Tamiya often includes Torque Tuned motors, shouldn't pinions get stronger as the included motors do? 

Okay, rant over. Seriously, what's up with the shaft lengths?  Does anybody know? 

 

[skom25]

I have no idea, but I found exactly the same issue in TT-02, when I wanted to use 3 mm motor plate. Shaft is so short, that it is not possible.

[Thommo]

 

Just enter "irregular shaft" in your preferred search engine and you'll find all the answers....    OK... maybe don't do that !  

[Mad Ax]

We had this issue with the control motors for Iconic Cup in M-chassis a few years back.  Off the top of my head I can't recall what brand they were - the later Team Powers were fine, but the earlier ones had short shafts and it was hard to get a pinion on.  Some of my pinions were quite wide, I had to replace them with narrower ones.  It was pretty annoying that the motor chosen as the mandatory control motor for the class was so hard to fit in the class's most popular chassis.

[alvinlwh]

I posted this same problem I had with my DT-02 two years ago. It has the same gearbox as your DT-04 I believe? 

[Saito2]

5 hours ago, Juggular said:

Why are motor shafts getting shorter?  

I wish I had an answer but I feel your pain. Its really annoying in gearboxes like the DT where the pinion is mounted "backwards" like that. I like to run silvercans and Torque Tuned motors in nearly everything and won't join the brushless revolution. Cars like the Super Astute and Egress (at least fixable by using the Vanquish motor mount) won't take these shorter motor shafts. Even the pedestrian vintage Kyosho Car Crusher struggles with these dinky shafts. I had to buy a motor for my BBX just to get one with a long enough shaft. Money is tight and getting tighter making these extra expenditures to get kits up and rolling all the more annoying. Rant off.

5 hours ago, Juggular said:

Why is Tamiya still giving us pinions made out of cheesium?   

lol @cheesium. I think we have a new term for Tamiya pinions. All I can suggest is to go back and look at relatively recent past post on the subject. There are people that semi-support the use of aluminum pinions and even plastic bushings. Perhaps those supporters can offer some good reasons. My personal feelings on mechanical sympathy means I don't even consider using aluminum pinions and plastic bushings so I don't really give much attention to the arguments. 

[skom25]

46 minutes ago, Saito2 said:

Perhaps those supporters can offer some good reasons.

I would be more than happy to hear that too! 

I tried cheesium pinion once in TT-02, because steel/ hard coated was not available and I just wanted to run car. Bad decision. Pinion was not badly worn after few runs, but there was a lot of mess in gearbox: grease mixed with aluminium particles, despite I use only tiny amount of grease, just to make gears "shiny" and nothing more. 

[Sgt.Speirs]

9 hours ago, Juggular said:

Why are motor shafts getting shorter?  

...

Seriously, what's up with the shaft lengths?  Does anybody know? 

Tamiya wants you to buy the optional DT02 Alu Motor Heat Sink #53831  

With this you can rotate flipp the pinion (grub screw towards the motor)...

Edited April 29 by Sgt.Speirs
For a better understanding.

[El Gecko]

I don't know the answer, but I can commiserate. I also found that it's practically impossible to use a Tamiya (Sport Tuned) motor in a Tamiya chassis like the DT02. It seems that due to the shorter shaft, the Tamiya-branded sealed can motors will only really work with Hoppers and ORVs and possibly other vintage chassis. I honestly can't fathom how the DT02 would work properly with a silvercan out of the box.

[El Gecko]

5 hours ago, Mad Ax said:

We had this issue with the control motors for Iconic Cup in M-chassis a few years back.  Off the top of my head I can't recall what brand they were - the later Team Powers were fine, but the earlier ones had short shafts and it was hard to get a pinion on.  Some of my pinions were quite wide, I had to replace them with narrower ones.  It was pretty annoying that the motor chosen as the mandatory control motor for the class was so hard to fit in the class's most popular chassis.

The Team Powers Cup Racer V3 have a super short shaft as well. I tried to fit them in a DT02 without success, so they are boxed and stored waiting for some chassis they can actually work with.

[alvinlwh]

36 minutes ago, Sgt.Speirs said:

Tamiya wants you to buy the optional DT02 Alu Motor Heat Sink #53831  

With this you can rotate the pinion (grub screw towards the motor)...

Actually you maybe into something. Insert spacers equal to the thickness of the motor plate between the gearbox and motor and you get a even shorter shaft allowing the pinion to be flipped. 

[Sgt.Speirs]

@alvinlwh: Not maybe…that‘s it (I mean the motor plate, not the spacer option)😉

And it‘s also shown in this way in the manual of the DT-02MS

 

 

By the way, I had the same issue with my Dyna201 gearbox and the Torque Tuned motor: My Post on Instagram

[skom25]

1 hour ago, alvinlwh said:

Actually you maybe into something. Insert spacers equal to the thickness of the motor plate between the gearbox and motor and you get a even shorter shaft allowing the pinion to be flipped. 

There are only 2 screws holding motor and I am afraid, that using spacers instead of full plate can break gearbox.

[No Slack]

My problem was that by mounting the grub screw facing the motor the shaft gave me a problem aligning the pinion with the spur gear. This was when using the alu motor mount. (Allen key would not fit). So I used a Carson Black motor with a long enough shaft and mounted the pinion the original way. Result.

[skom25]

13 minutes ago, No Slack said:

My problem was that by mounting the grub screw facing the motor the shaft gave me a problem aligning the pinion with the spur gear. This was when using the alu motor mount. (Allen key would not fit). So I used a Carson Black motor with a long enough shaft and mounted the pinion the original way. Result.

In DT-03 or car with the same gearbox? Manual clearly shows what to do.

[Kowalski86]

30 minutes ago, skom25 said:

There are only 2 screws holding motor and I am afraid, that using spacers instead of full plate can break gearbox.

On top of that, two very short, plain screws without much area for the heads to really "grab". Most 2wd buggies will use washers or large flathead screws to retain motors.

10 hours ago, Juggular said:

Steel will last forever. But for the most part, these 2000 series are strong enough (unless you want to run a 6000KV motor on 3S).  Why couldn't Tamiya include these?

I guess because Tamiya offers steel 17t/19t pinions as hop-ups?

I ended up running a Kyosho 14T 550 and a Robinson Racing pinion in my EVO (same gearbox). RRP pinions are even wider so it barely bites the tip of the motor shaft. I gave up on running silver cans and Torque Tuneds due to how hot they would get.

[skom25]

@Kowalski86 do you think that shaft is long enough, to use that Kyosho motor with motor plate and Tamiya pinion?

[Kowalski86]

3 hours ago, skom25 said:

@Kowalski86 do you think that shaft is long enough, to use that Kyosho motor with motor plate and Tamiya pinion?

It's the same length as a silver can motor if not a millimeter longer, your setup should work fine if not better than my own sketchy setup.

[Juggular]

 

@Sgt.Speirs showed that this is a design issue!  My goodness. It's an amateurish design! (It's a 20 year old design, though).  

The motor is pretty much at the dead center to balance the weight of the chassis.  If they didn't want to move it, the spur gear should have stuck out a few mm. So the grub screw would be closer to the motor. (Created a problem, and then selling the solution isn't a sustainable practice, Mr. Tamiya.. lol..)  

I wouldn't have minded if they used a separate motor plate (A7 below) and sold an aluminum upgrade separately like MF01X. 

While they were at it, they should have cut a window to vent some heat.  That cup that looks like it's holding the motor. But it's a heat-cage.  The structural support is entirely from those BA2 screws.  Might as well have a window cut into it.  

(I was going to drill several holes. But I got lazy after 1 hole.  I should just saw off a square.)  

I doubt that Tamiya will change the mold.  1) New molds are expensive. 2) Cutting a window might mean using a slide mold, which is even more expensive. 3) Changing this won't sell more kits. 

 

As for the motor, it dawned on me that it could just be the standard measurement.  16mm is 1/2 inch (edit: see below).  That was the length of my 550 & brushless. (I wrote as much yesterday. But it didn't occur to me that most newer shafts might be in standard.)  Tamiya's newer motors are 8mm, which is 1/4 inch (edit: see below).  Bearings for 540 motors are in standard too, not metric. 

I'm pretty sure older motors had 10mm shafts.  Maybe Mabuchi used to measure in metric?  When they outsourced it, maybe they went with full standard since 540 is traditionally in standard?  The supplier might have said, "we sell motors to Japan as well as the US. We have to use standard, but if you want 10mm (which is between 3/8 and 7/16), we'll charge 5 cents more per motor." (Engineers would have to reset tools back and forth. Humans make mistakes. They have to throw out if they do, etc, etc.) We know Tamiya won't give us a 40 cent pinion.  So they just went with simpler standard lengths of 1/4 inch (edit: see below).  To be clear, it's just a guess.  

 

[rich_f]

On 4/29/2025 at 9:31 PM, Juggular said:

As for the motor, it dawned on me that it could just be the standard measurement.  16mm is 1/2 inch. 

No it isn't - 12.7mm is half an inch. 16mm is quite a lot more than half an inch.

On 4/29/2025 at 9:31 PM, Juggular said:

Tamiya's newer motors are 8mm, which is 1/4 inch. 

No it isn't - quarter inch is 6.35mm. 

I find it quite amusing how you call imperial measures 'standard' when metric is also a standard, just a different one, and in fact it's the standard used by most of the world. 

I don't have anything to offer to the motor shaft length question, I just couldn't stand to see incorrect assertions.

[Saito2]

1 hour ago, rich_f said:

I find it quite amusing how you call imperial measures 'standard' when metric is also a standard, just a different one, and in fact it's the standard used by most of the world. 

I think @Juggular is using the term "standard" as shorthand for the US Standard Measuring System. The term Imperial units of measurement was used by the British empire. We just say "Standard" (rolls of the tongue better than saying US Standard Measuring System every time) or "Metric" in the States to differentiate as both units of measure are commonly used at times over here.

I agree, going by the actual definition of the word "standard", the metric system would be the standard used by most of the world by far.

[Kowalski86]

On 4/29/2025 at 8:06 AM, Sgt.Speirs said:

Tamiya wants you to buy the optional DT02 Alu Motor Heat Sink #53831  

With this you can rotate flipp the pinion (grub screw towards the motor)...

I'd buy one if they didn't cost more than buying a new brushed motor!

If I have one complaint about the DT series it's how picky the gearboxes are. You need something with just the right shaft length, a pinion thats just the right width, and your motor can't be lower than 25 turns or it will burn up. Once everything is installed its fine, it's just clearly made with a specific pinion and motor setup in mind.

[Juggular]

2 hours ago, rich_f said:

No it isn't - 12.7mm is half an inch. 16mm is quite a lot more than half an inch.

No it isn't - quarter inch is 6.35mm. 

I find it quite amusing how you call imperial measures 'standard' when metric is also a standard, just a different one, and in fact it's the standard used by most of the world. 

I don't have anything to offer to the motor shaft length question, I just couldn't stand to see incorrect assertions.

Fair enough.  You are right in that 2.54cm is 1 inch. I knew that. I got that wrong and must be corrected.  16mm is almost exactly 5/8th of an inch.  Which means 8mm is 5/16th.  Maybe Mabuchi used 7/16th?  (We are not so good at the imperial fractions ourselves.  Many Americans thought 2/3rd pounder burger was smaller than a 1/4 pounder.  So A&W 2/3 pounder failed.  I know.  Our average IQ is 98 when the Japanese IQ is like 104 or 106.  The median IQ is always 100. But scholars compare those median numbers between countries.  We are lower than the world's average.)  

I agree that the "US Standard system" is silly.  I was an army brat, so I've heard kilometers or "clicks" all the time.  When NATO uses 120mm shells, our shells shouldn't be 120.85mm (or 4 3/4 inches).  The world's "Standard" is metric.  When it comes to engineering, imperial is really complicated.  In fact, I think most manufacturers use metric now, even in the US.  Ford and GM use metric, even a furnace company like Carrier does too.  But most people have metric and imperial wrenches at home because of old stuff and construction things. 

For timber, inches are larger and easier increment.  When people need to replace some wooden planks on their floors that were built in 1950, it's easier to simply keep making things in inches. 30 inch doors will forever be 30 inch doors until you knockdown the doorjamb.  Even so, you'll only have options of 28, 30, 32, 34 or 36 inch wide doors.  I haven't seen metric timber or doors in the US.  Some old systems do stick around like airplane pilots and sea captains using knots when measuring air speed. 

I'm not really defending the imperial system, especially fractions.  The 2 other nations that uses imperial system is Liberia and Myanmar.  That's how unpopular imperial system is. (We don't like the word "imperial," because that is reminiscent of the "British Empire." Even though the British abandoned it themselves.  So we say "standard." But obviously, that's just us.)   I wish we've gone metric in the 1970s... (we did try, but it should've been done from teaching children over a couple of decades, not simply swapping road signs in kilometers.)  

I have not solved the mystery of why 540 is not in metric (the only imperial bearings I have are 1/8 x 3/8 x 5/32 bearings for 540 motors, which is why the pinions we buy are made for 3.175mm shafts).  I thought 0.4, 0.6 and 0.8 module gears were complicated, but Tamiya also uses things like 48 pitches (in imperial).  It's a mess.     

Anyway, we make fun of our "standard" ourselves, because we know how silly it is.    

 

[alvinlwh]

6 hours ago, Juggular said:

Even though the British abandoned it themselves.  

Not strictly true. Our road distances and speed are in miles. Our beer and milk are sold in pints. Our timber are still called "2 by 4", labelled as 50 x 100 but really is 38 x 89. Babies are weighed in pounds and oz. Don't even know what a stone is myself, which stone? Stonehenge. Stone of Scone? Height are given in ft and in. 

Then there are tyres, 225cm wide, 55% high and goes on 17 inches rims. 

[Juggular]

2 minutes ago, alvinlwh said:

Not strictly true. Our road distances and speed are in miles. Our beer and milk are sold in pints. Our timber are still called "2 by 4", labelled as 50 x 100 but really is 38 x 89. Babies are weighed in pounds and oz. Don't even know what a stone is myself, which stone? Stonehenge. Stone of Scone? Height are given in ft and in. 

Then there are 44

225cm wide, 55% high and goes on 17 inches rims. 

OMG, you guys are as messy as us. Not surprising since this land used to be the colony.  

I get the tires, but what's 44?