Crt ?
 

To anyone that has a crt not the mini but the full size crt. I'm trying to use brian's calulator but i need to know the diff ratio for the FR & RR diffs . Thank's

IIRC it's 3.31:1

Bye:018:

Yeah, the stock crt uses 43/13 diffs.

Thank's guys. What size spur are people running in the CRT ?. I would like to use mike's CRT truggy mount .

Well, you could look at is this way:

Situation #1

Stock 3.31:1 diffs + stock steel 62 spur + 14-16 pinion= worn out pinions every other run.:035:

Situation #2

HB LSP r&p 4.3:1 diffs + kyosho plastic 46 spur + 14-16 pinion= happy pinions:018:

Hope this helps!

Bye:027:

Im definetly not gonna buy new diffs . The CRT im getting sunday is brand new & unused. What about the ofna 51t spur ?.

This is what i got using the ofna 51t spur & stock diffs.



post:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 51
Pinion Tooth Count: 12
Total Voltage: 14.8
Motor KV: 1853
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.0092
Spur/Pinion Ratio: 4.25 : 1
Total Ratio: 14.05769 : 1
Tire Circumference (inches): 17.28 inches (438.88mm)
Total Motor Speed: 27424.4 RPM
Vehicle Speed: 31.92 MPH (51.28km/h)
Effective Speed Rate: 2.16mph/V (3.46kmh/V)
Effective KV Value: 1853

Not necessarily. The key to long-lasting pinion is a solid and consistent mesh. Both Mike and I (and maybe others) have run steel on steel with very good results. I've run my Hyper8 for about 10-12 packs' worth and the pinion still looks very good. The only downside to steel pinions is the cost compared to regular pinions.

Yes, I know that, but not everyone has got the money for hardened steel pinions and can achieve an absolutely perfect and consistent mesh.

@rchippie
- you would only need the ring and pinion gears, not complete diffs....

Bye:018:

*EDIT* Brian, actually when I had a dual HV-maxx e-maxx I ran a RRP 65t hardened steel spur with kyosho pinions and had no ill effects at all over many, many runs. But, when I put RRP pinions on (just to change ratio) the pinions lasted maybe 3 runs at most. Weird:confused:

here are the results with a 60 amp load using a 51t 12 gearing.
Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 51
Pinion Tooth Count: 12
Total Voltage: 14.8
Motor KV: 1853
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0
Motor Current Draw: 60
Motor coil Ω: 0.0092
Spur/Pinion Ratio: 4.25 : 1
Total Ratio: 14.05769 : 1
Tire Circumference (inches): 17.28 inches (438.88mm)
Total Motor Speed: 26401.54 RPM
Vehicle Speed: 30.73 MPH (49.36km/h)
Effective Speed Rate: 2.08mph/V (3.34kmh/V)
Effective KV Value: 1783.89

Were the pinion teeth shaped the same? Remember, some have different pressure angles, which can make a HUGE difference in pinion longevity.

Yup, shaped the same, standard 32p. Maybe the RRP pinions were aluminum and not steel? IIRC, I thought they were steel, I think traxxas ones are at least...

Bye:018:

After talking with mike & brian this is what im going with. The motor is a 9XL

post:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 62
Pinion Tooth Count: 16
Total Voltage: 14.8
Motor KV: 1853
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0
Motor Current Draw: 60
Motor coil Ω: 0.0092
Spur/Pinion Ratio: 3.88 : 1
Total Ratio: 12.81731 : 1
Tire Circumference (inches): 17.28 inches (438.88mm)
Total Motor Speed: 26401.54 RPM
Vehicle Speed: 33.7 MPH (54.14km/h)
Effective Speed Rate: 2.28mph/V (3.66kmh/V)
Effective KV Value: 1783.89

Actually, I told hippie he needs to send me his truck, but he didn't like that idea. :)

Dont be made :005: . Brian what do you think of my last post about yor calculator ?.

Sounds good to me - nothing looks bad. I just want to see it finished; that's the true test. :)

A little off-topic, but have you figured out your buggy delimna, or are you going to scrap it to do the truggy?

The mugen is on hold for know that im getting the truggy LOL:005: . I might make it nitro again .

Nitro? What's that? Oh, I know - you must want a slower buggy. ;)

LOL:005:

For those that have a CRT or anyone else. What are your opinion' on battery lay out ?. I have two 2s2p packs, i was thinking about one pack on each side or would it be better to put both packs together so they are the size of a 4s pack on one side ?..

My E-CRT has been through three revisions. I'll save you the long story and say this:

1.) NO WAY to make it work without a motor mount like Mikes (something with the motor and diff on the same metal!) I had a 2 pc and it was a nightmare.

2.) Hot Bodies Ring & Pinion help with gearing. Currently I've got the HB R&P on the Diffs and the Kyosho 46T Spur mating up with a 10T Centrury Pinion all running on 4s...I'm currently using one of those mystery XLT-1 Motors which I think is somewhere around a 6XL or 7XL.

3.) I've had the batteries in both the one large block and the side by side setups. I prefer the side by side...the truck feels more balanced.

Here is a photo of my current E-CRT...
http://visionarycomputer.net/rc/IMG_6031.JPG

Looks like a true racer to me!

Remember to shoot pics once the schulze tries to become liquid..

Ha...you know, I have had plenty of trouble with the Schulze but this year it's been running much better (it was factory serviced over the winter) The TrakPower's are new and I ran for a new record this weekend, about 20 mins at fast practice pace with no thermal! I would LOVE to replace it but until the MMM or R1MT ships it will stay right there...you can't see the holes in the body which basically blow air right on it (hence it's ultra high mount) - I'd rather finish than gain a small amout of lower CG.

DM

Mac thank's for your repliy, your battery layout is what i was looking for. I plan on ordering mikes truggy mount, because im going to use the stock spur & start with a 16t pinion. Acordding to brians calucator that should get me around 32mph.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 62
Pinion Tooth Count: 16
Total Voltage: 14.8
Motor KV: 1853
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0
Motor Current Draw: 60
Motor coil Ω: 0.0092
Spur/Pinion Ratio: 3.88 : 1
Total Ratio: 12.81731 : 1
Tire Circumference (inches): 17.28 inches (438.88mm)
Total Motor Speed: 26401.54 RPM
Vehicle Speed: 33.7 MPH (54.14km/h)
Effective Speed Rate: 2.28mph/V (3.66kmh/V)
Effective KV Value: 1783.89
__________________

16T sounds very high to me. Back when I was running the steel spur and stock CRT Diffs I was trying to get as small a pinion as I could find. I see an old order from Mike for 10T-13T. I was running the 10 (yikes). Perhaps it was b/c my motor was too hot...I'd likely suggest you start at 13T and go up or down from there...

i will be using a 9XL for the motor. I have a 13t pinion. Be sure to look at the chart above.

Here are the stats with a 13t pinion. They dont look to bad .

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 62
Pinion Tooth Count: 13
Total Voltage: 14.8
Motor KV: 1853
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0
Motor Current Draw: 60
Motor coil Ω: 0.0092
Spur/Pinion Ratio: 4.77 : 1
Total Ratio: 15.77515 : 1
Tire Circumference (inches): 17.28 inches (438.88mm)
Total Motor Speed: 26401.54 RPM
Vehicle Speed: 27.38 MPH (43.99km/h)
Effective Speed Rate: 1.85mph/V (2.97kmh/V)
Effective KV Value: 1783.89

No harm in trying what you have before you plunk down any $$. If the 13 feels way off, you know a 16 may be more what you need. If it's close try a 14 or 15. I'm pretty sure when I first tried my CRT I bought a 15 and a 20! I thought I'd need the speed, settled down with a 10...Much of it also depends on where you are using it. Often, crazy speed on a track isn't as valuable as instant accel...try, experiment and above all, enjoy!

DM

Very true :027: i would at least like two pinions so i have a choice at different tracks. Are the chassis stiffiners on the side , if so do they really work ?.

Yes, they are. You know how RC is, often times you are at the track and someone's "day job" is something exciting. There is a machinist who comes to my local track. When the CRT was eating pinions 1 per 2 runs (seriously, but the one piece mount and plastic spur has fixed that) he saw that flex in my mount was likely the problem. He gave me these two strips and I put one on each side. The truck certainly feels more rigid to me but I don't really know - for the slight weight I figure it's good insurance.

DM

How does it feel when you hold the truck by each end & try ti flex it ?.How thick are they ?.

Mac when you fliped your diff around using the stock spur did you have to mod the chassis ?.

It seems to me that they basically move the flex point away from the center and push it out a bit closer to where the F&R assembly bolt up to the chassis. Stiffer - but essentially transfers flex somewhere else. Flex has not been an issue for me since the change to a 1 piece m/mount. The flipped diff as a rev-3 change and by then I was already using the 46T...

DM

I just wanted to make sure you know this, the kyosho 46t spur fits up with the stock jammin diffs. I'm using it in my Jammin CR project.

Good News
 

I got my CRT today woohoo :005: .

Mac what are you using for battery tray's, are they custom or did you buy them ?.

Both I guess...Mike C made them for me...awesome. I thought he was going to put them in the store but I've not seen them. Word of advice, drill the plastic but DON'T tap it...just thread it with your screw...

DM

That makes sense. Plastic "gives" enough that tapping is unecessary. I don't think I've seen any stock plastic parts pre-threaded. Plus, that extra snugness acts like threadlocker.

^Exactly, the point of not tapping plastic is so the added friction of it being just big enough helps to hold the screw tight.