DX3S RPM Sensor Installation Instructions

healthyfatboy · 01-13-2009, 08:21 PM

Okay, I thought about it for a long time last night and finally came up with a plan on how to get this sensor to work. Hopefully someone comes up with a better way to install the sensor and if you do, please let me know how you did it so when I go to install this on my Spec racing Slash, I'll do it right!
Anyway, this installation should work for the Rustler, Slash, Bandit, Stampede, or any Traxxas vehicle that uses this stock transmission case. You can still use the gear cover without any modifications.
Tools you should use: Dremel, CA, and maybe a pencil and drill.
Tools I used: Drill, hobby knife, CA.

First:

You need to form out a hole that is almost identical to the shape of the sensor. If you could get it exact, that would be ideal but with the sensor wires where they are, it can be difficult. As you can see, the hole I made looks like trash because I only had a drill and hobby knife. Maybe I'll ask for a Dremel from my wife next month for my birthday. Anyway, I hoped that I could just cut a slit for the mount to go on but that didn't work because the sensor was sticking out to where it would interfere with the spur gear.
CAUTION: I used an 83 tooth spur. If you use a different one, where you cut the hole may need to change. You'll have to figure that out yourself. That's what the pencil is for, to figure out where to cut the hole.

I put the reflective sticker on the back of the spur. Be sure to use a little CA as the sticker won't stay otherwise.

It's at the top in the picture but difficult to see. I tried a head on shot and the reflection was such that you couldn't see anything.

Once you get your hole cut out correctly, you should be able to put your sensor circuit board right in. I haven't glued mine in yet as I'm trying to figure out the best way to do so. If you Dremel it out perfectly, then it should fit very well and not have any problems.
This is how it looks installed on my truck from one side. Sorry it turned out bad. The flash from my phone reflected off quite a bit from the clutch plate.

This is with the spur back on.

You can put the gear cover on after you do all the calibration and such.

From the other side.

I tested it out before gluing it and it worked just fine. I really think this is the best place to put it if you plan on keeping the gear cover on. I tried to think of other ways to mount it even with the cover off but with the spur being rounded on the outside and no good mounting locations, I decided to go in from the back. I'm sure there are other ways of doing this but I couldn't think outside the box well enough. If you come up with another idea, please post as I would like to know how others have done it.

Good luck and hopefully you'll have a Dremel to make it cleaner!

VXL Beast · 01-13-2009, 08:28 PM

Honestly, that is ingenious! Very, very cool! So, have you tried it? What RPM's are you getting?

got_nitro · 01-13-2009, 08:37 PM

Nice install!!

I used the back of the shock tower to mount the pick up and put the reflector on the D/S yoke so i could change the size of the spurs.
I'll see if i can get some pics up for ya HFB.

healthyfatboy · 01-13-2009, 08:40 PM

Well, on the 3S 3200mAh 15C TrueRC battery, I tried it out and got some numbers. Before I get to it though, I have to say when I did the calibration, I rolled it out so the spur spun ten times, measured the distance, divided by 10 like I was supposed to and entered it in. Don't know really how accurate it is but with it propped up so I could try it out without going outside, I got roughly 9500 RPM which with the conversion measured out to 47mph. I'll have to get the GPS out at some point and see how well it works later but we'll see when it's warm outside.

healthyfatboy · 01-13-2009, 08:43 PM

got nitro, definitely post some pictures if you can. I don't change too much on my Rustler and I don't care for crazy speed so I don't really plan on changing the spur very often but I couldn't find a way to mount it otherwise. I like the idea of using another rotating object as the mounting point. Looking forward to what you have!

got_nitro · 01-13-2009, 08:45 PM

Quote:

Originally Posted by healthyfatboy

I like the idea of using another rotating object as the mounting point. Looking forward to what you have!

The only problem i have with it where i installed it is that it dosent take the balooning effect into perspective. So at high speeds it's a bit off

Compared to the bushnell it's about 7-9mph off.

Yours will never be off on speed unless you change tires and forget to recalibrate it..

EDIT::: OOPS yours could be off as well because of the balooning effect as well...

healthyfatboy · 01-13-2009, 08:53 PM

You can't really take the ballooning effect into account. You could calibrate it with using the gear ratios and tire diameters but then you would need to take the tire circumference when ballooning into account. I think you would either have to live with the setting one way or another. If you want to know the correct top speed, then use the ballooned diameter. Otherwise, use the normal one if you won't be driving around too fast everywhere.

got_nitro · 01-13-2009, 08:55 PM

Exactly^^ But its always going to be a lil off on top speed.

Because i want it set at normal tire size..

got_nitro · 01-13-2009, 09:28 PM

HFB, Im having trouble uploading these pics off my memory stick onto my new H/D. Old one crashed on me 2 months ago. If i cant get them up tonite ill get them up tomorrow 4 ya..

traxxasfan1 · 01-13-2009, 09:42 PM

hey heathyfatboy AWSOME IDEA!!!!!!!!!!! thats how i am going to mount my sensor. but have just one question, is the sensor 1/8 of an inch away from the spur like the manual says??

cchriste · 01-13-2009, 09:49 PM

Wow...that is cool.

healthyfatboy · 01-13-2009, 10:25 PM

It's about an 1/8th of an inch. If the PCB board is flush with the case, then it's pretty close. Before you glue it, put the spur back on and run it to see if it works and if it does, you can CA it. If it doesn't, reposition it some until it does. Mine is probably close to an 1/8th of an inch but I doubt it exact. It's good enough for it to work.

traxxasfan1 · 01-14-2009, 07:28 AM

ok thanks. i think i might just use the screws that come with it to hold mine on

got_nitro · 01-14-2009, 08:59 AM

T/Y HFB <--edit oops,

These are shots of a VSM on a rear tower but you can do the DX3 the same way if ya want. My DX3 parts are waiting to be installed on my new project/chassis.

Hardware i used,

Cant really see the sticker/magnet in these shots but it's C/A stuck to the yoke.
Mounted, The green board you see is the pick up.

I drilled a small hole in the bottom of the shock tower to screw in the extention.

healthyfatboy · 01-14-2009, 09:26 AM

Is that just a battery bar extension or are they actual spacers? I really like the idea and will most likely use it on my Slash instead since I won't have to drill into the transmission case. My idea works well but my problem with it is if you take it off, you have to cover the hole somehow. That could be a problem. Thanks and let me know about the extension and what size it is so I can pick some up at the hardware store or wherever you go it.

got_nitro · 01-14-2009, 09:31 AM

Quote:

Originally Posted by healthyfatboy

Is that just a battery bar extension or are they actual spacers? .

LOL, it looks just like a battery extention dosent it

I got lucky and found it in a H/W bin @ the LHS. It was 5c lol. Im sure you could fab up a different extention piece but i deff needed it for it to clear the yoke and to give it enough room for the magnet to spin. In the shot with the washers/h/w, i used the smaller one on the back side of the pickup to extend it further out. I needed 3-5mm of room for the p/u to read it.

healthyfatboy · 01-14-2009, 10:45 AM

Okay, I'll probably take my truck into the hardware store and find some spacers that will work well with it. I'm sure I can get something to work pretty easily with what they have there. Thanks for the helpful advice! I would rather not have to cut a hole in the transmission case! I'll have to see how well mine works and if it comes off, I'm going to the yoke where it's an easy install. I was getting close with my thinking! I was wondering what else rotated but knew the wheels wouldn't work. Should have thought about the shafts as well!

got_nitro · 01-14-2009, 10:55 AM

N/P Dude, post some pics when your done!! It's an easy install, should take about 5 min if ya get the right parts "spacers/extention" from the LHS.

Is your install going to be on a brand new slash?

healthyfatboy · 01-14-2009, 11:19 AM

I got it for Christmas so it's pretty new. Has 12 runs on it and all ready for spec racing this weekend. I only have 1 receiver though with telemetry so if I end up using it on my Slash (assuming they allow it, pretty strict there) I'll move it over to the Slash instead. I'll try to remember to post pictures when I'm finished. Thanks for the help!

xhardwarex · 01-14-2009, 03:57 PM

Quote:

Originally Posted by got_nitro

T/Y HFB <--edit oops,

These are shots of a VSM on a rear tower but you can do the DX3 the same way if ya want. My DX3 parts are waiting to be installed on my new project/chassis.

Hardware i used,

What a sec! You didn't use me, oh nevermind.

healthyfatboy · 01-15-2009, 11:17 PM

got_nitro,

I just installed it on my Rustler. Here's the picture.

I was about $2 worth of parts and took some time to do since I was watching the Office at the same time but it seems to work well. If it quits working, I can always raise or lower it pretty easily which I like.

The problem with it is that now I have to patch up the hole in the transmission case. I used some duct tape so hopefully it will be good enough.

jolynsbass · 01-16-2009, 12:00 AM

That's pretty sweet! So, you get to see how fast you're going (approximately) as you are driving? Sheesh, what won't they think of next?

rc!!! · 01-16-2009, 12:43 AM

Quote:

Originally Posted by jolynsbass

That's pretty sweet! So, you get to see how fast you're going (approximately) as you are driving? Sheesh, what won't they think of next?

duct tape a cheetah to the car, to try to get more speed!

cheetah's are slow vs rustler vxl's... haha

there pretty fast vs humans... but we can build somthing faster...

got_nitro · 01-16-2009, 05:21 AM

That looks awesome HFB!!

DiFabio42 · 01-16-2009, 06:30 AM

Sweet!!!!!!!

z-class88 · 01-16-2009, 09:08 AM

Quote:

Originally Posted by healthyfatboy

got_nitro,

I just installed it on my Rustler. Here's the picture.

this is pretty smart thinking HFB , but i think the people with the steel yoke might have a problem b/c you will have two black spots b/c of the screws. but you'll be fine on yours ......

sasquatch95 · 01-16-2009, 09:45 AM

do you mind if i do that???

healthyfatboy · 01-16-2009, 11:48 AM

Quote:

Originally Posted by z-class88

this is pretty smart thinking HFB , but i think the people with the steel yoke might have a problem b/c you will have two black spots b/c of the screws. but you'll be fine on yours ......

Actually, it won't be an issue at all as you would typically need to install a black sticker anyway. Instead of measuring how far it rolls in 10 revolutions, you can just do it in 5 since there are 2 black spots on it. That is assuming the sensor picks up well from the screws.

One thing I did notice with my setup is that the measured rollout was about 130" divided by 10 which doesn't exist in the radio adjustment for speed. It only goes up to 12.0 so my readings are going to be off a little but that will all depend on the outer diameter of your tire. In this case, having the steel yokes would be better. I may stick another sticker 180 degrees from each other so the sensor picks it up more.

sasquatch95, I don't care if you do it that way but the credit goes to got nitro as it was originally his idea. Thanks got nitro!

got_nitro · 01-16-2009, 11:54 AM

NP dude, im just glad you are happy with the mounting location and that it works for ya!

"not that i didnt think it wouldnt"

got_nitro · 01-16-2009, 11:58 AM

I was thinking, get some wax paper and cover one side of the hole in the trans case and fill the void with hot glue. Should turn out nice and debris/water tight for ya.

healthyfatboy · 01-16-2009, 01:12 PM

Quote:

Originally Posted by got_nitro

I was thinking, get some wax paper and cover one side of the hole in the trans case and fill the void with hot glue. Should turn out nice and debris/water tight for ya.

Excellent idea! Now I need to see if my wife needs a hot glue gun for any of her little projects...

z-class88 · 01-16-2009, 01:56 PM

Quote:

Originally Posted by healthyfatboy

Actually, it won't be an issue at all as you would typically need to install a black sticker anyway. Instead of measuring how far it rolls in 10 revolutions, you can just do it in 5 since there are 2 black spots on it. That is assuming the sensor picks up well from the screws.

^^^^ very true. i did not think of that

Quote:

Originally Posted by healthyfatboy

One thing I did notice with my setup is that the measured rollout was about 130" divided by 10 which doesn't exist in the radio adjustment for speed. It only goes up to 12.0 so my readings are going to be off a little but that will all depend on the outer diameter of your tire. In this case, having the steel yokes would be better. I may stick another sticker 180 degrees from each other so the sensor picks it up more.

130" seems kind of far.. im wondering if i did my e-revo the right way..

you start at zero with the front tire and end at 130 with the front tire correct!!

dragonfly · 05-29-2009, 10:56 AM

You measure the rotating part that has the sensor on it rolling 10 times.
Not the tire rolling 10 times. But yes if you measure with the front tire then the start and finish is measured from the same spot on the truck. I dropped a line off the body with a weight on it and then rolled it along my tape measure.

dragonfly · 05-29-2009, 09:28 PM

But I guess if you are measuring off the yoke it would be 10 times rotation of the tire.

Hoss138 · 05-30-2009, 04:24 PM

Hey Guys,

I dont have any pics of it yet. I installed the sensor on the inside of the RPM gear cover with a spacer and a dab of shoe goo. I run the wire out of the hole and replace the dust cap. I got about 49" of rollout. My stock setup with a 7.4 2s LiPo batt says about 17 mph. I checked it with my gps and that seemed about right. Does that speed for a stock setup sound right? I have not had the chance to run my new toy with any other Slash trucks.

Hoss138

healthyfatboy · 05-30-2009, 05:22 PM

Your installation sounds pretty interesting. Definitely put some pictures up when you can.