Mike sells 1/8inch bore Mod1 Pinions. He also sells the 5mm bore Hardened Steel pinions that are for use with steel spurs. I'm quite sure he will be able to make you a hardened 1/8inch bore pinion.

I already have the regular 1/8" bore Mod1 pinion, but it's for plastic spurs. But after reading posts where the hardened steel spurs don't last, I am hesitant to use them. I'm just trying to find a way to use a plastic spur on a diff that won't fit it. I might just email Mike and see what he thinks...

Ooo...this is going to be a pretty big obstacle...let me know what you do Brian.

Oh, I will. I emailed Mike to see what he thinks.

Great pics... cool.

Now I have a some questions....

1.How mcuh too short is the outdrive... with the kyosho gear shaved down? It looks pretty close. I wonder if it would work with the inside of the kysoho gear also shaved thinner (on the inside, the area around where the o-ring is)

That's an idea. I wonder how I'm going to do this while still making it perfectly even and flat?

There's actually one more measurement I need to take and post a pic of...

Nevermind the above pic..... you already said the stock bearing is 10mm.

Also I measured the stub on the kyosho which is right about 10mm. It's just a hair under 10 then tapers to just over 10. I wondered if you could use a spacer sleeve to make the stock bearing fit right on the kyosho... and fit at least part way onto the fat part of the stub. Just a little sanding on the stub and the bearing would fit. That would let the stock outdrive fit farther into the diff... maybe enough to work.

Make sense???

The problem then is that it's still a mod1 gear and you are using a MM. 1/8" bore mod1 gears are a pain... maybe Mike could hook you up with a spacer so you can use the 5mm gears.

I know that even if all that worked... the gear might rub on the diff mounts.. so you would have to do something to hold it from hitting the mount

Here's another picture showing the relative heights. Each spur is resting on a standoff of the exact same height. The standoffs are sitting on the gear mounting plane. You can see that I can't shave enough off the Kyosho spur for the outdrive to reach inside the diff enough, while still being able to use a bearing. Don't forget, I'm limited by the length of the outdrive, not so much the diff mount...

http://scriptasylum.com/forumpics/crtp5_diff_10.jpg

And even if I could get this to work, I'm still stuck trying to find a bearing...

Would be nice to replace the whole thing with a slipper diff with standard 48 or 32p gears. But I don't know one that would work at the moment :)

I think I would do the piggyback gear... with a 46t gear so you can line up the teeth perfectly and drill holes to bolt them together. It would look interesting but it would work great.

dude on ebay i saw a person calld like world of bearings he sells like frm R/C bearings to skateboards and so on.

Oh man - That is a real downer about that spur gear. I'm so glad you are posting all of this because it's nice to see everyone's feedback for when I start my project...speaking of which. Guess what I happened to track down at one of my LHS's? :027:

http://members.cox.net/gluena/crt05_3.JPG

I scoured the internet looking for one and hear it was in my back yard!
I know Brian already showed his next to his Jato but here are some more comparisons:
Next to it's big brother CRT
http://members.cox.net/gluena/crt05_6.JPG

And an 18t, GT2
http://members.cox.net/gluena/crt05_9.JPG

Like Brian I was thinking about a MM4600 or 5700 too but it looks like there are quite a few issues to work out with the metal spur and finding a 1/8 in bore Mod 1 pinion. Anyway, just some other thoughts:

Again just for size comparisons. Here is a Feigao 7XL and Maxamps 3S 4000 mah pack in place
http://members.cox.net/gluena/crt05_1.JPG

a 7XL on 3S, that will fly! it was fun in my maxx.. so it's fun in a 1/16th!

Oh yeah! I sent Mike an email about this last night and he said the CRT.5 is one of his "short listed" projects since he got one of these himself! :) He said he may have to make a custom spur setup or maybe another diff setup, but wasn't sure yet.

I still won't stop thinking about solutions, but at least there are others that have this now so I'm sure an ideal solution will present itself.

Riceman: Good for you! :) The CRT looks nicer in person doesn't it? So, when's yours going to be done so I can "borrow" ideas? :)

Brian, why not make a sleeve to use the stock bearing. Just make a sleeve out of some kind of composite to sort of fill the gap since you can't find a bearing the right size.

Yeah, I might just do that. But I still need to find a replacement outdrive yoke because it is too short to use the Kyosho spur.

The easiest solution I think would be to shave all the teeth off the stock spur and use the plastic spur the way I did in the pic below. Then, use several 2-2.5mm screws and screw the stock steel spur to the Kyosho spur. This would let me use the stock bearing and stock outdrive. All I would need to do is shave the chassis a little so the gear won't rub.

http://scriptasylum.com/forumpics/crtp5_diff_2.jpg

Seems like a good idea, but since it would be pushing the gear closer to the servo assembly, wouldnt it be hard to get the pinion on the motor since its already near the end of the shaft?

I thought that at first, but after measuring and test-fitting, it looks like it will work with a whole 2-3mm to spare. :)

I responded to Mike asking if he had some 1/8" bore Mod1 hardened steel pinions, or sleeves to use with the 5mm bore ones. I also showed him the dual spur thing. Maybe he can make an adaptor plate for the diff cover and then attach the plastic so it's like my idea...

Or just like you said round off the stock spur gear and drill your own holes - i wouldnt see a problem in that, id personally countersink the stock steel spur for 4 screws, and use nuts on the plastic end of the spur. I cant wait to order my crt .5 up!

LOL. I would do that, but the stock spur is hardened and I don't think I can drill the holes nor shave off the teeth. :)

Thats true, but i have a mill which will make it easier, yet still, i hate working with hardened material, really messes up my drill bits:mad:1 ..

No such luck here - just an overworked dremel. :)

if you drill first a 1mm hole and then go up every time with .5mm till you have a 3mm hole I think that will work

because i drilled bigger holes in my hardened rear wheel axle of my buggy (2,5 to 3mm)

I tried it with a 1/16" bit and I couldn't even get it started. It's one of those DeWalt Ti bits too and it was brand new.

Yea...hardened steel is a PITA to work with.

I'm hoping someone finds a solution by the time I get my CRT .5 :p

Whoever does pricing at Tower sure is on crack:

http://www2.towerhobbies.com/cgi-bin...&I=LXPRF3&P=ML

$420 for the same truck you can buy from Ultimatehobbies.com for $275

Wow, I guess! I thought they would've lowered the price to a more marketable level once they got it in stock. Maybe the pricing people are pricing the KIT like a RTR and don't realize it...

So have you come up with a solution to the spur gear problem yet?

Yes and No. Time for more pics I guess...

OK, so the stock outdrive wasn't long enough. I got an 1/8th scale Ofna outdrive set. It fits, but there was too much length after the pin, so I ground down the end until it was perfect. Man, the Dremel tool is totally indispensable! Anyway, the pic below shows the size differences.

http://scriptasylum.com/forumpics/crtp5_diff_11.jpg

Then I noticed the hole for the pin is bigger on the modded cup, but luckily, the stock gear has spots for two sized pins. And even more lucky is that a Revo wheel hex pin is the perfect length/diameter to fit. :)

http://scriptasylum.com/forumpics/crtp5_diff_12.jpg

The 1/8th scale outdrive mounted on the Kyosho spur:

http://scriptasylum.com/forumpics/crtp5_diff_13.jpg

The assembled diff. Fits perfectly! I did have to use two Ofna gaskets to get the right amount of play in the diff though. Note the stock 10x13x4 bearing on the 1/12th scale side and the 8x16x5 bearing on the 1/8th scale side. More on this later.

http://scriptasylum.com/forumpics/crtp5_diff_14.jpg

So now I am going to have to get/make some type of dogbone adaptor that will have a larger end for the now larger diff cup and the stock smaller end for the rear-end cup. You can see the size difference below between the stock shaft and a Sportwerks dogbone set. Not much difference in shaft diameter - only 0.06mm.

http://scriptasylum.com/forumpics/crtp5_diff_15.jpg

I figure I can either cut both shafts and use some type of collar to join the ends (grinding a flat spot and using a set screw), or have a new dogbone made to size. Below are a couple of examples of what I mean. Note; these are doctored images...

http://scriptasylum.com/forumpics/crtp5_diff_16.jpg

http://scriptasylum.com/forumpics/crtp5_diff_17.jpg

Remember the size difference between the bearings on the diff? Well, I ground 0.5mm all the way around one of the plastic diff mounts to accomodate the larger bearing. Took a while to get perfect, but not difficult.

However, with the Kyosho spur, the diff is physically about 3mm longer. So, I have to drill new mounting holes in the chassis. Not a big deal really, but the new holes would be VERY close to the existing holes and I don't like that. So, I think I'm going to enlist Mike's services once again to machine an integrated diff mount and motor mount. There really is not much room to play with between the front and rear braces so options are limited. The good news though is that he also has a CRT.5 so I won't have to ship mine out for test fitting. :)

Nice work... what would be sweet is to find a CVD type center shaft that is the proper length. The diff end would fit the modded center diff outdrive and the other end would have the u-joint, which I'm guessing would work on the other end? (assuming the .5 is made like big brother...)

But... you can probably make the custom shaft like in your pic. I cut a dogbone and shortened it for my Kyosho conversion. I used whatever material I could find that fit the bill... I think it was an aluminum handle from a pick. And I used a piece of steel tubing also, then put pins through it. Amazingly it's worked great... it's not the prettiest thing, but it has not failed yet. :)

The rear diff post size (the part that the cup is hooked to) is 5mm on the CRT.5, while 1/8th scale posts are 8mm...

i don't understand why not try 5mm shaft motor with steel motor gear?

Well, there have been a number of people who have tried it and the pinion doesn't last long at all despite the fact it is hardened steel. Read this thread for more information; RCM Mike even has his take on them.

ok, i think that is not a problem.
pinion gear maybe try use like SCM-21 steel materials with "Heat Treatment" process.

we have alot people convert X1CRT to BL with stock steel spur not problem.
gear not eat and great.
it's look like http://www.rcbig.idv.tw/bbs/rcbig/upload/18059-2-1.jpg

Here is some driver CRT stock gear clip.
http://www.youtube.com/watch?v=sajULgawAgo


so i think maybe gear is not a problem , this CRT.5 can more easy to convert right?

Yes, it would be much easier to convert. :)

I've been talking to Mike (owner) and we've been throwing ideas back and forth, so there IS a solution. I just want to find the "right" one.

That backflip on flat ground was pretty impressive.

Huh?

In andywpj's youtube video that he linked to (post #154), one of the cars does a wheel stand which ends up being a full backflip, I don't think I've seen that before.

They were speaking Chinese (I'm 1/2 Chinese, and can speak Mandarin fluently). The last 10 seconds or so the camera guy is saying "one more time" in reference to the backflip. :)

Looks pretty awesome. I'm hoping my .5 will do the same.

Anyone happen to know the inner diameter for the bearing used on a standard 1/8 scale center diff?

Not sure about the bearing...

What I am sure about is that those trucks in the video had spooled center diffs and kinda low gearing... man tha thing was super punchy.. but no much on top