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Old 08-11-2014, 07:07 AM   #526
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metal nut, play around with the shims on either side of the diff (the large 10mm ones). I found putting more shims on the side opposite the diff ring gear made my gearboxes much smoother and removed the notchiness (it moves the ring gear away from the bevel)

Also, they will quiet down after running
I thought about and tried that, but as soon as I add 0.2mm more (so one more shim), the whole diff binds in the lower case as the big bearings are too far apart. 0.1mm isn't much better. Did you shave the cases to allow for the wider diff?

And did the top half of your gear box allow all bearings to sit properly? I measured it this morning and the diameter of the space intended for the inner/smaller of the two small bearings is 0.5mm smaller in diameter! You can see with the naked eye that it's too small even. I think that's binding that bearing and pushing the bevel gear over enough to cause gear binding too, even after I shaved it.

Run the gearbox for an hour, eh? *sigh*
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Last edited by metalnut; 08-11-2014 at 08:13 AM.
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Old 08-11-2014, 08:39 AM   #527
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Well, I'm about 8 hours into the build and I'm still at the top of page 6. For the life of me, I can't get the rear gearbox to be smooth. I've shimmed and reshimmed everything dozens of times.

I have a 0.1mm shim behind the small bevel gear (separating it from the two bearings), and 0.6mm of shims between the outer/larger bearing and the end of the input shaft to keep things from moving around. As far as I can tell, this is as far away as I can move the bevel gear from the ring gear. Still, it sounds like something is lopsided because there is a slight notchy interference every few revolutions.

Furthermore, the top of the gear box is shit. First, it doesn't align properly with the bottom, so I sanded it flat but it's still not perfect. Second, the way it was moulded wouldn't let the smaller bearing on the input shaft to be properly seated. I had to shave a bunch of plastic to let the top of the case close down on the smaller bearing. The gear diff bearings also get squished noticeably, even if just placed into the top case by itself.

When I screw it all down... it's shit. I've been very careful, pre-tapped everything, applied the least amount of force to the screws, etc., no go.

Has anyone else had these problems? I'm giving up for the night, but I feel like I just threw $500 into the mud. Ridiculous issues at this price point.
At this point, I would replace the gear case. You shouldn't have had to do any of that.

The gear diff is slightly wider than the ball diff. The carbon reinforced cases are slightly narrower than the standard plastic ones. The Evo6 has both, so getting the side to side clearance right will require minimal shimming. ICRC one of the boxes I built used -0- shims.

My suggestion is (and this goes for any TB derivative) to build the gearbox per the manual, with the exception of adding 0.3mm of shims on the outside of the case, between the input shaft and the bearing. This reduces the pinion plunge and makes the box a little freeer. Getting all the run out shimmed out of the driveline also has a side benefit of making the driveline quieter than it otherwise would be.

Some of the 40 tooth gear sets had that notch you describe. IMO the problem is in the ring gear. The first time you run the car under load (actually drive the car), the gear set will bed in and the problem evaporates.
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Old 08-11-2014, 09:01 AM   #528
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At this point, I would replace the gear case. You shouldn't have had to do any of that.
Ugh. I took a look at the case on the second parts tree, I tried to put the smaller bearings in and the same problem exists: the inner bearing hole is definitely not wide enough, the bearing doesn't fit even under moderate pressure. When I join the 2nd set of case halves together, they too rock side to side across where they touch in the middle. So that problem also exists in both sets.

Could I have gotten a bad batch of carbon cases? I have no problem with ordering new ones, but I'm skeptical that they'll be better

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Originally Posted by CraigMBA
The gear diff is slightly wider than the ball diff. The carbon reinforced cases are slightly narrower than the standard plastic ones. The Evo6 has both, so getting the side to side clearance right will require minimal shimming. ICRC one of the boxes I built used -0- shims.
Good to know, I haven't tried that yet. I kept the side-to-side (so gear diff) shimming per the manual. I'll see what it feels like without the 0.2mm shim

Quote:
Originally Posted by CraigMBA
My suggestion is (and this goes for any TB derivative) to build the gearbox per the manual, with the exception of adding 0.3mm of shims on the outside of the case, between the input shaft and the bearing. This reduces the pinion plunge and makes the box a little freeer. Getting all the run out shimmed out of the driveline also has a side benefit of making the driveline quieter than it otherwise would be.
I can try this again, but when I had 0.3mm of shims between the bevel gear and the smaller bearing, the gears bound badly. I'll try to use only 0.3mm outside the case (for a total of 0.6mm) to see what that feels like.

Quote:
Originally Posted by CraigMBA
Some of the 40 tooth gear sets had that notch you describe. IMO the problem is in the ring gear. The first time you run the car under load (actually drive the car), the gear set will bed in and the problem evaporates.
Good to know. Alternatively, I was thinking of buffing the gears. I have polishing attachments for my dremel, at low speeds I've had good success with that method before. In fact I was thinking of doing the same to the metal gears on spur/shaft.
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Old 08-11-2014, 10:01 AM   #529
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If the casings don't mate with the bearings fully seated in I would try to get the thinnest gasket paper you can get (I have some 0.3mm thick), oil it a bit and make a gasket to join the two halves. That way you can keep it leak free too.

If the problem is that the bearing doesn't fully seat in the casing (hole diameter too small when casing halves joined), I would turn a brass disc that fits in the bearing seat, stick it on a shaft and in the dremel, join the case halves over it and use grinding paste to open up the bearing locations until they sit nice and snug.

Dude, instruction manuals are just a suggestion. If things don't work, time to bin the instructions and do whatever it takes to make things work. Especially shimming. Do you really imagine Tamiya moulds everything to an accuracy reserved for crankshaft bearings?!

I don't understand why you would follow the manual when it obviously doesn't help (by your report).

Do your own shimming such that things work nice and smooth and forget the manual.

Don't buff the gears. If things are a bit crunchy, just run them in with a bit of fine grinding paste (use common sense).
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Old 08-11-2014, 10:03 AM   #530
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Can you take a picture of your transmission, with the top cover removed, but the differential and input shaft installed? Basically, take the six screws holding the cases together off, separate the cases, and post pictures of them both?

Because something is up here....I own seven of these chassis that use this style gearbox, and I've never had that much trouble with one much less two.
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Old 08-11-2014, 10:54 AM   #531
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I'm meeting with a Tamiya expert (and TCS champ) at lunch to show him what's up, he put together an EVO.6 recently so I'm in good hands. I'll report back what he says. I'll also take some pictures for you gentlemen tonight.

Apologies about the headaches, I'm coming from an Xray T4 where everything fits with computer-like precision out of the box. Even my Spec-R R1 had very good fit and finish. I was just expecting more from a $500 kit, that's all. I think it's the TB03 cases that are the only real issue.

Stay tuned.
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Old 08-11-2014, 10:58 AM   #532
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Do any of you guys know how to remove the flange bearing
From the spur gear holder? Just thought that I will seek
The advise and reduce the slop problem.
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Old 08-11-2014, 03:27 PM   #533
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Ok, so I met with my guru friend. Here are the results

1. His transmission cases also rocked side to side a bit, so he sanded down the middle portion that was the high point. That lets the cases rest on the points which the screws go through. I did the same but sanded the whole surface. I'll try using shims around the screw hols to separate the two halves a bit, starting with 0.1mm all around and going up if needed.

2. He believes he's using 0.1mm shim on the side of the gear diff, so I'll try that as opposed to 0.2mm. I tried no shim and the diff definitely spins more free, but the grinding noise of the gears is increased (since the ring gear isn't pushed over as much anymore, I presume).

3. We came to the conclusion that my top gear cases are deformed, specifically where the smaller/inner small bearing fits. I'll take pictures of this tonight. It looks like it's meant for a 9mm bearing, not a 10mm one. He's never seen that before, his were fine. I'll have to get new cases and hope I don't get ones from the same bad batch.

To summarize... I hope Tamiya releases aluminum gear cases soon. Charge $50 per set, I don't care, take my money.
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Old 08-11-2014, 05:48 PM   #534
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Apologies about the headaches, I'm coming from an Xray T4 where everything fits with computer-like precision out of the box. Even my Spec-R R1 had very good fit and finish. I was just expecting more from a $500 kit, that's all. I think it's the TB03 cases that are the only real issue.

Stay tuned.
That is really quite disappointing.

I've not got one, but in comparison, everything on my 418 fits amazingly well. Easily as good as a T4.

I had plastics last on a TA06 (carbon reinforced stuff) and that also fit like a glove.

Don't blame you for crying out for alloy bulkheads/casings, was surprised it didn't have them to be honest and is what stopped me pressing the buy button at Banzai a few weeks back.

Hopefully there is a Maezumi Style! in the near future and it has these. That will be much harder to resist buying.
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Old 08-11-2014, 08:07 PM   #535
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Ok, so I met with my guru friend. Here are the results

1. His transmission cases also rocked side to side a bit, so he sanded down the middle portion that was the high point. That lets the cases rest on the points which the screws go through. I did the same but sanded the whole surface. I'll try using shims around the screw hols to separate the two halves a bit, starting with 0.1mm all around and going up if needed.

2. He believes he's using 0.1mm shim on the side of the gear diff, so I'll try that as opposed to 0.2mm. I tried no shim and the diff definitely spins more free, but the grinding noise of the gears is increased (since the ring gear isn't pushed over as much anymore, I presume).

3. We came to the conclusion that my top gear cases are deformed, specifically where the smaller/inner small bearing fits. I'll take pictures of this tonight. It looks like it's meant for a 9mm bearing, not a 10mm one. He's never seen that before, his were fine. I'll have to get new cases and hope I don't get ones from the same bad batch.

To summarize... I hope Tamiya releases aluminum gear cases soon. Charge $50 per set, I don't care, take my money.

Alloy cases would be shit heavy. Nobody uses such a thing and that includes 1/8 nitro buggies, etc.
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Old 08-12-2014, 12:30 AM   #536
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Nevermind. Heat guns can solve all kinds of problems. Stay tuned for details.
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Old 08-13-2014, 12:58 AM   #537
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So I wanted to post a quick updat. I got a bit frustrated last night and threw my Evo up for sale. Well, my Tamiya buddy let me have a set of his carbon transmission cases and they are definitely better than the ones that came with my kit. Not perfect, but better.

Then I had a revelation. I tightened the transmission screws about 50% and hit the whole assembled case with the low setting on my heat gun. Every 10 seconds I'd stop and tighten the screws a bit, until they were nice and snug. I heated the case one more time and let it cool. The idea was to let the heated up plastic untweak itself under the pressure of the screws, conforming to the lower half and to the bearings inside. And it worked!

There is still a bit of gear to gear roughness here and there, but with some creative shimming it's minimal. What's more important is that the whole transmission spins MUCH more freely, to the point where I'm satisfied with it until the breakin. So looks like my build is a go. Hope this tip helps someone else in the future.
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Old 08-13-2014, 01:01 PM   #538
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If I wasn't going to TCS finals next week, I'd buy that kit. A steal at that price.

On edit, glad you figured it out!
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Old 08-13-2014, 02:43 PM   #539
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Originally Posted by metalnut View Post
So I wanted to post a quick updat. I got a bit frustrated last night and threw my Evo up for sale. Well, my Tamiya buddy let me have a set of his carbon transmission cases and they are definitely better than the ones that came with my kit. Not perfect, but better.

Then I had a revelation. I tightened the transmission screws about 50% and hit the whole assembled case with the low setting on my heat gun. Every 10 seconds I'd stop and tighten the screws a bit, until they were nice and snug. I heated the case one more time and let it cool. The idea was to let the heated up plastic untweak itself under the pressure of the screws, conforming to the lower half and to the bearings inside. And it worked!

There is still a bit of gear to gear roughness here and there, but with some creative shimming it's minimal. What's more important is that the whole transmission spins MUCH more freely, to the point where I'm satisfied with it until the breakin. So looks like my build is a go. Hope this tip helps someone else in the future.
maybe have Steve at STRC or Mike at Exotek make aluminum versions of the cases? forfeits TCS eligibility, but hopefully minimize this heartache?
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Old 08-13-2014, 06:33 PM   #540
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maybe have Steve at STRC or Mike at Exotek make aluminum versions of the cases? forfeits TCS eligibility, but hopefully minimize this heartache?
I've reached out to Exotek before for a similar request, but they can't justify the R&D, tooling and manufacturing expenses for kits with very small market share. The EVO.6 is a unicorn, I doubt we could get them to make anything, especially since the cases would be complex to design and manufacture. Economics :-(
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