Jammin CRT .5 Project
 

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!
http://members.cox.net/gluena/crt05g.JPG

Diff cup for rear differential and 8 x 5 mm bushing
http://members.cox.net/gluena/crt05b.JPG

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.
http://members.cox.net/gluena/crt05a.JPG

I had to Dremmel the front chassis brace a bit to make room for the center diff moving forward 1-2mm.
http://members.cox.net/gluena/crt05e.JPG

Bench test setup with 6 cell NiMH pack
http://members.cox.net/gluena/crt05c.JPG

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

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!

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.

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...

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.

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.

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.

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.

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

update- it's rolling
 

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.

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

Update
 

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.

Here are the pictures of the underside with the diff mounted up.
http://members.cox.net/gluena/CRTScrewsb.JPG

and a close up
http://members.cox.net/gluena/CRTscrewsa.JPG


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.

http://members.cox.net/gluena/padslogo2.gif
http://members.cox.net/gluena/CRTpainta.JPG

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

Nice one!

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

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! :)

I was able to get mine out to the track last week and put a couple packs through it. I also ran my nitro GT2 that day. I must say that the 12th scale truggy outhandles the 2WD Stadium truck in every way. So forgiving it almost makes me forget how bad a driver I really am :027: My first lap with the .5 was a bit disappointing. I broke a plastic ball end on my front turnbuckle on the first jump. Completely my fault as I landed the jump nose down. Luckily I had a spare that happened to fit. No other issues after that.

So here are the pics of the now dirty truck
http://members.cox.net/gluena/crt02.JPG

Luckily the Kyosho spur did not have any fitment issues. I did not need to raise the diff mounts or dremel the opening. It's close but I have not seen any evidence of bidning or rubbing yet.
http://members.cox.net/gluena/crt01.JPG

My "not as nice as Brian's" battery tray. Temporary and I will eventaully redo it to put some tabs in front and back but this gets me up and running for now.
http://members.cox.net/gluena/crt03.JPG

With the 2s2p 8000mah lipo installed.
http://members.cox.net/gluena/crt04.JPG

First lap and first real jump at the track and I broke the plastic ball end on the letf from turnbuckle. Luckily I had a suitable RPM replacement in my sapres.
http://members.cox.net/gluena/crt05.JPG

Weighing in at 4 pounds and 9.8 oz including 2s2p 8000mah maxamps lipo
http://members.cox.net/gluena/crt06.JPG

A couple minutes of back yard bashing. Apoligies for the video quality. The only cameraman I had available was my 7 year old son.
<object width="425" height="350"><param name="movie" value="http://www.youtube.com/v/dyNGNumuPVs"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/dyNGNumuPVs" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"></embed></object>

Cool video. Looks like so much fun. I'm surprised that the kyosho spur fit so well. If I remember correctly, BrianG had fitment issues with it. With it being so light, and with that set up, you should be getting some amazing run times. :027:

looks great. good to see that you were able to use the kyosho spur even if you had to alter the frame a little.

Great conversion and its a great video too!

handles jumps nicely but the transmission is very noisy is that normal for this?

Apologies for the video quality are not needed. Just like watching and episode of NYPD Blue :027:

If you could, can you tell the the approximate price you paid for the conversion like the MM system, crt.5 (which I can't seem to find a place to buy it for around $250), servo, etc?

Greatly appreciated.

I got my .5 at my LHS for $259. Calif and San Diego County sales tax was a killer at 8.75%. I don't think you're going to do much better than this. It seems to be the best going rate online.

I went with a Hitec analog MG servo for about $30. You can go digital for a little bit more.

Batteries: run what ya got or get some Lipos of you are feeling adventurous/

Looks like Mike has the 1/8 inch bore mod1 pinions back in stock for $12. And the 46t Kysoho spur set me back another $5.

Everything else I had in hand already and cannibalized from my T4. MM 4600 system and Spektrun Rx.

Thanks for the info and the links. $170 is also the cheapest that I have seen. I have a 6 cell pck from my stampede that I sold (in sig) so I would really only need to buy the crt.5, MM 4600 or 5700 (esc and motor) and the servo, and then all the small parts.. but that doesn't really count in my book, lol.

Well, sorry for hijacking the thread, and thanks for the info.

Its all yours!! :027:

It's actually a bit cheaper on tower with their coupon codes on their homepage rght now. Without being a super saver member, it'd be $253.98 shipped. Being a super saver member, I can get it for $239.99 shipped right now.

Well here is mine at the track - The first three and a half minutes is me getting the feel of the truck going around. The last segment is a friend of mine driving (he's a much better driver) and really shows off how nicely this thing works it's way around. I secretly had my motives for letting him drive:017: I can now study his lines and how he manages the track. I especially noticed how nicely he rolled the double table top as opposed to me landing it on the top of the second one.

http://www.youtube.com/watch?v=ppPSCyHWIs4

I love it!! I think this truck is perfect for the electric world. It seems quite durable, great at handling, and is less expensive to convert than a 1/8th. I want one so bad!!! Nice job.

Sweet video. I need to post my rc18 for sale some place where I'll get a good price for it. I really need one of these CRT.5's. :027:

What kind of run times do you get with that 8000 battery?

NICE!!! how does it compair to nitro truggies?

This might have already been posted but check out the nitro version here

The handling on mine is outstanding.. and with execption of the center diff mods it is completely stoclk.

For those of you putting yours together you might want to look at Jammin Jay's setup I'm going to give the 1000-1000-500 diff fluids a go and re-set up my suspension to match his. That should be good for starters. I really want to get this on the track this weekend against the 10the 10th scales and see how it matches up. I think the only real limiting factor will be my sucky driving skills!

Some Speed Runs!


Gearing is 13t/46t. Still have the 4600 in it but went up to a 3S 6000mah Lipo pack. Diffs are now filled using Jammin Jay's setup. It still doesn't look very fast in the video. In person though it is plenty fast.

Well - I think I just jinxed myself in the other .5 thread. I said how cool everything was running and I would try gearing up. I did and I think I overdid it. I went up a tooth on the pinion to 13t (with the 46t kyosho spur) and put a 3S cell in which is the configuration that I ran the speed runs with. No problems with heat on the short speed bursts. However, this is not a good combination at the track. ESC did shut down on me after about 5 minutes of run time and motor was close to 200 :026:. I would like to keep the 3S and perhaps drop the gearing back down. I didn't have any other pinions with me at the time so I'll have to try again another day.

In all honesty man, after watching the vid I think its safe to say if it went any faster it would take off. That is a missile of a buggy- accellerates like I dont know what & the steering is impressively sharp. I would say 12/46 or 13/48 is as tall as you could get away with without destroying something expensive.

I dropped down to 11t/46t combined with 3S lipo and I think this is the ticket for my track.:027: I went through almost two full packs before a run in with an 1/8th scale buggy and the end of a long straight did me in. Rear upright and rod end broke off sending the wheel and CVA flying off. I wish I had someone to video as it was finally performing as I had hoped it would. Temps were acceptable with the motor in the 150-160 range and the ESC at about 110. Battery was under 100. I'll definitely try to get some video the next time out.

That sounds great. You should really watch out for those 1/8 buggies. They can be dangerous.:005:

I didn't realize till after I glued the tires to the wheels but do you guys think that the wheels that use the pins will withstand the brushless power? I kinda wish I had used the ones with hexes.

They should be fine. Associated B4's and T4's along with Losi XXX's only use pins and they have no problem with BL power.

Would re-inforcing the area around the pins with plastic epoxy help make them a little stronger?

project update
 

It's been nice reading everyone else's input to their .5 builds. The motor and gearing issues of particular issues. I've been running 12t/46t with the 4600 on 3S and it does tend to get on the warm side in the 160-170 range after 15 min or so on the track. Then again my shell is closed with no air flowing through so that could be a big contributor to that. We'll see as I will head to the track today with the new 2.2 Snake Eyes truck tires installed. I've also put a heat sink on the motor. The RPM receiver box is a new addition that now safely houses my rx and UBEC.

New Shoes: Proline mounted on Associated GT2 wheels.
http://members.cox.net/gluena/crtse1.JPG

http://members.cox.net/gluena/crtse2.JPG

http://members.cox.net/gluena/crtse3.JPG

http://members.cox.net/gluena/crtse4.JPG

http://members.cox.net/gluena/crtse5.JPG

With the added rotating mass of the truck tires I can now do this!

I'm off to the track this afternoon to see how the new tires work there. Report to follow.:027:

Double back flips! Im impressed....