RC Monster Speed Estimate Calculator
 

Hey all,

I just got done inputing all of my setup data into the RC Monster Speed Estimate Calculator and I came up with some discouraging numbers.

I'll be running:
FLM Emaxx conversion
1/8 scale HB diffs
72T spur
17T pinion
5.5" tires
hardened steel tranny gears (standard emaxx gearing)
18.5V 5S Lipo
1700Kv Neu 1515 2.5D motor
Quark 125 Monster Pro ESC


Sounds good right? The speed estimate for this setup is 17mph. Is this correct?

Well, the thing that's hurting your speed is the HB diff ratio of 4.3:1. Can you use a smaller spur and/or a larger pinion? That's the only way I can think of to increase your speed other than using larger tires or slightly higher voltage. Even if the spur/pinion ratio seems off, it's really the final drive ratio that matters...

BTW: You can use the export button on that page, which will open a window that will allow you to copy/paste the results into your post.

Yea, use the buggy diffs not the truggy diffs. 13/43 vs 10/43 makes a HUGE differance. Also ditch the 72T spur and run the 66T and use something more like a 24 or 26 tooth pinion. I was running stock diffs with a similar setup and was able to run 24/70 all day befoire I went to the Mod1 gears. With 13/43(3.08) buggy diffs you could probably run 24/66 without a problem. I think thats the max that the stock motor plate will allow gearing wise. But if you need 26T pinion just dremel the slot in the motor plate longer and you shouldnt have a problem.

I looks like you had that setup for the most conservative gearing you could possibly do.

I thought about that too. Problem is that even with different gearing and larger tires I only gain a few mph.

In my other maxx I have basically the same setup except for the Novak HV Maxx 4.5 and I ran the calculation. It was within 4mph of what my telemetry unit indicates (35-40mph). I have also validated those numbers with a handheld GPS.

Glad to hear that is pretty accurate.

As to the gearing, I would do what jhautz suggests. If you don't already have the diffs, get the buggy ones instead. Going from a 4.3:1 to 3.3:1 make a bit of difference. Then, play with the spur/pinion. That motor and voltage should be easily capable of 45mph+ with the proper gearing.

Thanks for the help and information.

if i where you for more speed i would go to 51t spur with strobe that should definatly get you alot more speed.

With the rpm the motor is doing you'll need about 14:1 final drive ratio to do 40mph (maybe less, depending on voltage drop), and the setup you posted has about a 31:1 ratio. Just changing the diffs to buggy ratio ones gets you to 24.1:1, so that's the first thing that need's to be changed.
Then go to around 66/24 like jhautz said to get 15.66:1 and around 35mph.
If you already have the truggy ratio diffs (I hope you don't) then you need 51/24 to get the same ratio, and that would be about the fastest you could gear it (that I know of).

Yeah...I see new diffs on the horizon. But I am also changing directions as to which ESC/brushless setup I will use. Thanks.

Say, SSSP; i was just going through your web-album; is it me, or is your transmission sitting too high in the front?

http://lh3.google.com/image/ssspconc...JPG?imgmax=800

Auch! is that the lunsford pillowball in the titanium draglink of the UE saver? I broke on while tightening them; i don't know the english word for it, but if you put two materials of the same rough structure into eachoter (which are a tight fit) they will grab onto eachother. I broke one, and got a replacement from Lunsford. Luckely i could drill it out and tap the hole M3 again. (which is a PITA on titanium)

Yeah it was a little high...actually both of my FLM chassis and trannys had the same problem. I had to dremel a small amount of metal off of the tranny and chassis so everything would fit. The gap you see in the photo is due to the beveling of my amateur machine work. If you were to see it from the side profile, the tranny is now flush and level. I notified FLM about a few of their minor "defects" but they have not been too eager to respond back as to whether they plan to "fix" the problems in the future. I am still pretty happy with their products.

It is a Lundsford ball...titanium. I think the word you are looking for is "binding." I too broke one off in the back bulk of my first truck...big time pain in the @ss to fix. I never want to go through that again.

Not exactly explained as a simple binding; it's the titanium/materials microstructure grab into eachother.

Could the word you're looking for be "seizing"?

2 a : to cohere to a relatively moving part through excessive pressure, temperature, or friction -- used especially of machine parts (as bearings, brakes, or pistons) b : to fail to operate due to the seizing of a part -- used of an engine

So the problem you're talking about now is a Ti pillow ball in a Ti turnbuckle head?