Ofna Hyper ST Conversion! - RC-Monster Forums

BL_RV0 · **Ofna Hyper ST Conversion! -** 06.23.2008, 01:42 PM

Hey guys, this is my first "big" brushless conversion. I am going to the LHS in about an hour to go put my deposit for my Hyper ST pro kit! They don't have it in stock at the moment, so I am going to put a deposit on it, and if I get there before noon, they can have it in by tomorrow!

. My planned setup is the RCM mount and battery tray, Neu 1512 3D/F, MMM, and Protek 5s 4000 LiPo. Planned gearing will be somewhere around 52/16. Here is what I got when I calculated it.
Differential Ratio: 3.909090909090909
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 52
Pinion Tooth Count: 16
Total Voltage: 18.5
Motor KV: 1700
Tire Diameter (inches): 5.8
Tire Ballooning (inches): 0
Motor Current Draw: 70
Motor coil Ω: 0.012
Spur/Pinion Ratio: 3.25 : 1
Total Ratio: 12.70455 : 1
Tire Circumference (inches): 18.22 inches (462.82 mm)
Total Motor Speed: 30022 RPM
Vehicle Speed: 40.78 mph (65.5 km/h)
Estimated Adjusted Speed: 39 mph (62 km/h) - 5% loss
Effective KV Value: 1622.81
KT constant: 0.8 oz-in/A
Motor Torque: 0.29 ft-lbs
Final Torque: 3.68 ft-lbs
Final Power: 1295 watts (1.7 HP)
Hopefully the little 1512 will run cool in this truggy, because it is light. I still need to figure out what shock/differential oil I will buy. Any suggestions for a mostly bashing truck, and some track driving, (it will be on the one I am building, and it will have huge jumps!) You'll definitely see some huge air! I'll get some pictures tomorrow, of the box and building. I found a video showing the contents of the box, and apparently the differentials are pre-built, (a big plus for me because building diffs, IMO, is a pain.) I am going to try to keep this thing as light as possible with the battery probably all the way forward, the motor obviously behind the center differential, the ESC in front of the motor, (or maybe behind, depending on how much room I have because the MMM is big,) and the RX behind the battery (Airtronics 92836) using the XR3i I got from Lincpimp (thanks) and probably a Cirrus P-CS701BB that I have laying around to take care of steering. Only thing is, I don't know where to get a servo arm for it because the servo head is nearly 1/4" wide! Any ideas? The truck will most likely run on motor brakes, only because I don't want to deal with servo placement and such, and as I said before, trying to keep this thing as light as possible. Any thoughts on the project as a whole?

brushlessboy16 · 01:52 PM

NICE start! why not gear it higher?

Where did you find your money tree? i have been looking for one

you might br able to use the stock throttle/brake servo if you chose to use manual brakes, just trim the servo tray

BL_RV0 · 01:54 PM

Somehow, stuff sold. Not quite sure how, but that was my first good luck in months.

I really want great temps, and long runtimes, so I didn't gear it higher. Any thoughts on shock/differential oil?

Arct1k · 01:58 PM

The diff's are not prebuilt - The spider is but only with grease so you have to take it apart anyway... That was my fun last night...

I'll be using the same battery pack and same KV motor but with a 1515 2.5d / MMM. I'm using a HS5595TG for steering...

This is so wierd - I've never heard of this conversion. Then I get one and two more people sign up for them the next week!

BL_RV0 · 06.23.2008, 01:56 PM

Yeah, who else signed up? Are the differentials easy(ier) to build than other cars?

Arct1k · 02:25 PM

Finnster is getting one - They are actually a little harder...

There is no big seal just a small o-ring which was a little bit of a pain to get it to stay on... not a biggie though

The spider is a different animal - unlike a normal diff the body is in multiple parts with long screws holding everything together. You have to put some grease over the screw holes to stop the diff oil leaking out when you are building it... With the spider it is a little fiddly with 6 gears but with a little time it seemed to go togther ok.

I built the front end last night and it mesh seems a little tight in diff case but hope it will wear in.

BL_RV0 · 06.23.2008, 04:09 PM

Hyper ST officially deposited-- In by 1:30 tomorrow!!

lincpimp · 06.23.2008, 04:50 PM

I would go with a higher kv than 1700 on the 1512, shoot for 2400kv or so. That way you can gear it lower and spin the motor faster. That will help with the lower torque that the smaller motor will produce. The motor wil still run cool, as the neu motors are fine over 40k rpm, plus the lower gearing will help with amp draw.