Jammin CRT .5 Project - RC-Monster Forums

riceman · **Jammin CRT .5 Project -** 04.05.2007, 01:58 PM

Well I've been riding the coat tail of BrianG's thread so I guess it's time to post my own. Here is what I have so far:

1. Like BrianG I'm experimenting with the 46t Kyosho Nylon spur. In doing so I did a couple of mods needed to do to accommodate the thicker gear. The main thing was using an LST2 axle outdrive cup. As BrianG documented the stock bearing is an odd sized 15mm od. With the Kyosho a more common 8 x 16 bearing can be used but the diff mount must be bored out 1mm to accommodate it. Everything else fit well after using 3 gaskets to get the ring and pinion mesh to turn without binding. The new center diff setup is now about 1.5 mm longer than stock so I elongated the chassis mounting holes to accommodate.

2. Now that the rear diff cup of the center diff is for an 8mm ball size dogbone I needed to match the rear and find a dogbone that would fit. Luckily I had both parts in hand. The rear diff cup is from an MGT differential and the 3” long 1/8th scale dogbone is from an HPI Savage. I ended up using two 8 x 5 bushings to fit the 1/8th scale diff cup on the 5mm CRT mini shaft. One of the bushings is slotted to allow the set screw to go through it and hit the pinion shaft. I’ll see if I can post some more detailed pics later.

3. The motor is a Mamba Max 4600 I robbed from my T4. The pinion is a 15t 5mm bore that I sleeved with a copper bushing. I drilled out the bushing to still allow the set screw to hit the motor shaft.

Some pictures:
Motor mount is rather crude right now. I'll clean it up a bit later. Not nearly the nice craftmanship as BrianG's!

Diff cup for rear differential and 8 x 5 mm bushing

Nice fit with the 3" HPI 1/8th scale dogbone. You can see the green fuel tubing I used in the CD diff cup to keep the dogbone deep in the rear diff cup. There is actually plety of room to work with with those 1/8th cups.

I had to Dremmel the front chassis brace a bit to make room for the center diff moving forward 1-2mm.

Bench test setup with 6 cell NiMH pack

Now it’s a matter of putting the rest of the truck together and getting the battery mounted and then on to some real world testing. For now here is a vid of the first bench test.

http://www.youtube.com/watch?v=JBzp7tUBjt8

BrianG · 04.05.2007, 02:54 PM

Nice job! Got any pics of the underside where you had to drill new CD mounting holes? I was thinking of doing this but thought the new holes would be VERY close to the existing holes and was concerned about strength. 1.5mm is not a lot!

riceman · 04.05.2007, 03:05 PM

Thanks - I didn't drill new holes per se. I actually elongated the existing holes as well as the countersinks. Again. not real pretty but it should hold much the same way engine mounts can be adjusted. The rear mount remains the same so it isn't likely to shift... I hope:002: I'll try to post more pics tonight.

BrianG · 04.05.2007, 03:08 PM

What you could do is put the screw in place with a nut to hold it on and JB Weld the nonused part of the elongated hole to make it a little strudier and less prone to shifting. Just an idea...

riceman · 03:15 PM

You read my mind! I thought about refilling the existing un used part with JB weld. I was thinking of mounting evertying up and putting grease on the screw so the JB would stick to the chassis and not the screw so the screw could still be removed.

I also failed to mention that I need to make up a new top plate. The stock one fit back on top after truning it sideways but it wasn't an exact fit. I went with it for the bench test as nothing was binding.

BrianG · 04.05.2007, 03:19 PM

Yeah, I forgot about greasing the screw. I suppose you wouldn't want it stuck there! :) Now that you mention it, I would also turn the screw from time to time as it hardens to keep the weld from sticking.

I already made my top plate, which is where the MM and receiver are going to go. I just didn't make it all pretty and paint it because I wasn't sure which CD solution I was going to use.

riceman · 04.05.2007, 03:46 PM

So are you going to try the stock metal spur for now? I really thought about doing this but that would be just too easy now wouldn't it? :005:

The other issue I'm having right now are very leaky diffs. Not only the center but the rear had a lot of fluid about it when I removed the rear bulk assembly. Gonna have to look into that some more.

Post up a pic of your top plate when you get a chance. I'd love to see it.

BrianG · 04.05.2007, 03:54 PM

Yeah, using the stock spur is the "easy" way out, but also the cheapest. ;)

To fix the leaky diffs, just pick up a set of the Ofna diff gaskets - they DO fit. I did have to carefully dremel (using a sanding wheel) away about 0.25mm on the outside of the gasket though to fit perfectly.

When all the other parts arrive and I know the top plate won't need adjustments, I'll finish it up and post pics. Hopefully, everything will arrive tomorrow or Saturday so I can get it running this weekend. My 5Ah cells are still on backorder, so I'll probably start with a 6 cell NiMH pack just to get it going. Still haven't quite figured out how I want to do the lipo tray yet.

jnev · 04.05.2007, 06:12 PM

It loks really nice. Can't wait to see it finished!!:027:

riceman · **update- it's rolling -** 04.06.2007, 03:30 PM

I've got a big grin on my face! I was up late last night mounting shocks and a temporary battery tray. I got it rolling at about 11:30 pm. Enough so to pull the unglued tires off the rim.:027: So tonight will be spent gluing up tires and shooting some paint on the body so I can really open it up.

BrianG · 04.06.2007, 03:49 PM

Glad to hear it! Now I'm really jealous!

riceman · **Update -** 04.09.2007, 11:36 AM

Still waiting for paint to dry on the shell. But tires were glued up and a couple of packs were put through in this weekend. Sorry no video yet. I need to find a cameraman and I couldn't tear my 7 year old son away from his legos to shoot it this weekend.

I'm running 12t/46t on the pinion and spur. I first tried it out with a 6 cell NiMH pack and it did very well. There is a bit of inbalance as the cells are on one side of the vehicle. Still not bad with the few jumps and it definitely outhandles my 2WD T4. I then got a little crazy and dropped a 3S 4000mah pack in (crazy because I still didn't have a body for it). Gotta say - I'm going to be liking this truck. The truck just handles great and jumps very easily. Very little mid-flight corrections. This with all stock settings and no tuning whatsoever with the exception of 30K oil in the center diff. All the mods are holding up so far. I hope to get it out on the track later this week.

I should be able to get updated pictures tonight with the newly painted body.

riceman · 04.10.2007, 01:49 AM

Quote:

Originally Posted by BrianG

Nice job! Got any pics of the underside where you had to drill new CD mounting holes? I was thinking of doing this but thought the new holes would be VERY close to the existing holes and was concerned about strength. 1.5mm is not a lot!

Here are the pictures of the underside with the diff mounted up.

and a close up

Here it is with the body finally painted up. I kept it pretty simple with a san Diego Padres theme. The one thing I forgot to account for was the stock yellow wing and wheels. I guess I'll have to eventually find a white one to match the scheme.

Dafni · 04.10.2007, 02:58 AM

Nice one!

I hope Proline comes out with a CP body for this truck!

BrianG · 04.10.2007, 10:26 AM

Your crt5 body is much better than mine! I just do a (poor) fade scheme; red in front, black in back. You'd think with all the time I spend on the internals, I'd do a better job with the shell, lol. Just not the artsy type. :)

Nice job though. How's she holding up? Did you have to raise the CD so the spur clears? Let's see more pics of the internals man! :)