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Old 03-03-2009, 03:09 PM   #46
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Any suggestions for gearing with a 17.5 BL motor ?

Genx with 1 cell SMC lipo 4000 mah and a TQcell booster.

The track is small.

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Last edited by Canuck; 03-03-2009 at 05:23 PM.
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Old 03-03-2009, 05:16 PM   #47
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Is it just me, or does anyone else find that particular wording a bit scary?
Just got back to this thread and read this. Very good point.
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Old 03-04-2009, 06:16 AM   #48
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Originally Posted by Randy_Pike View Post
If you're going to use an RX pack it really needs to be a 5 cell at 6v's. You can use this setup as long as you leave the esc switch OFF.
Randy, I just noticed this... any particular reason why you consider a 5 cell receiver pack as necessary? Mine seems to work fine with a 4 cell receiver pack.
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Old 03-04-2009, 09:30 AM   #49
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Trips,

It can work on 4 cell whichis 4.8v . 5 cell would offer 6v and provide more voltage for the radio and receiver. Both will work. I recomend 5 cell for higher voltage out of personal preference I suppose.
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Old 03-04-2009, 09:36 AM   #50
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I've been racing on 4 cells since the jurassic period, so I guess the higher voltage isn't something I'd miss... then again, i can get even lighter with a small 2 cell LiPO rx pack than a 4 cell nimh, so maybe that'll be the way I go when the time comes...
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Old 03-13-2009, 09:57 AM   #51
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Old 03-13-2009, 01:36 PM   #52
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speaking of new firmware

I have 189 in my RSpro for my sedan and 189 in my RS for my pan cars. Would there be any reason for my to udate the Sedan if I am not going to be going to 3.7V lipo? Would there be any reason to update the RS in my pan cars if I will be using 3.7V with a booster/rx pack?
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Old 03-14-2009, 05:28 PM   #53
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EDIT: I've added a set of diodes to the parts list, and I've updated the schematic to show where they go. This is in response to Team Tekin posting his concerns regarding the rather high voltage of two LiPO cells as input to the receiver and ESC. Thanks sharing your concern.

Okay, I've had my SMC 3.7 Lipo for a while now, but so far I've still been running 4 cell NIMH. I'd been having a hard time finding a suitable receiver pack that didn't cost an arm and a leg, and the Novak booster is yet to be available.

I decided I'd run the Lipo this weekend, and I came up with a pretty low cost, lightweight solution. I bought a couple of E-Flite single cell 110mah Lipos (the ones they sell for their Blade CX Micro helicopter). THese cells are TINY and weigh almost nothing. My original plan was to put two together in series to make a tiny 7.4v receiver pack. I took one of the cells out of the package, and tried to get the molded plastic end fitting with the integral plug off it (the tiny plug on this cell is incompatible with any connectors we normally use) I wound up shorting the contacts and that cell went poof.

So now I had only one cell left, when the idea hit me... We already have 3.7 volts from the SMC battery, why not just add the ONE tiny cell in series to give 7.4 to the receiver... I picked up a couple of servo extensions, and in about a half hour it was wired up and working...

Here's how to do it... but first...

WARNING!!! DO NOT ATTEMPT THIS UNLESS YOU ARE SUPREMELY CONFIDENT IN YOUR SOLDERING ABILITY AND HAVE EXCELLENT EYESIGHT FOR CLOSE-UP WORK ON TINY OBJECTS. DO NOT ATTEMPT THIS WITHOUT PROPER EYE PROTECTION AND PROPER FLAMING LIPO BATTERY PROTECTION.

I used a bucket of sand with a metal lid next to the bench... if I heard any hissing or saw any sign at all of the battery going to get weird, I'd just throw it in the bucket and close the lid.

You'll need one E-flite 110mah LiPO cell (or other suitable small LiPO cell), and two 6" servo extensions to do this. Here are links to the parts:

Battery

Servo extensions
Diodes

First step is to remove the white wire from both extensions, you won't be needing them so shave the weight... Now cut each extension in half, and strip a bit of insulation from the red and black ends. tin the ends neatly.

Now, VERY carefully, attach one lead with a male lug to the E-flite battery. This is VERY close work, and it'll be VERY easy to inadvertently short out the battery, so BE CAREFUL here. Put some heatshrink on the lead and shrink it after you're CERTAIN that you have made good solder connections. I'm not kidding about being certain... if one of thise wires comes off after the heatshrink is in place, that cell is going up in smoke, so BE SURE. with the cell on the bench, label side UP, red dot side DOWN, and the little connector pointing LEFT, the BOTTOM of the two contacts is the positive. double check if you have a multimeter with fine point tips. If you have one of those illumina1ted magnifiers to work under, it make this step quite a bit easier. Once again, if you're at all doubtful of your ability to produce good clean solder joints in VERY close quarters without shorting anything, don't attempt this!!

Now take the other lead with the MALE plug, and solder the BLACK wire to the NEGATIVE side of the deans plug that plugs into your SMC pack's deans socket. Splice the RED wire from this to the RED wire from one of the servo extension FEMALE sockets. Connect the BLACK wire from this female socket to the POSITIVE side of the Deans plug that goes into the SMC pack (yes this black wire DOES go to the POSITIVE, trust me) Now cut this black wire in the middle and splice the two diodes inline, with the striped ends pointing AWAY from the Deans plug. All your connections should have heatshrink on them, so go back and unsolder and reconnect if you forgot the heatshrink.

Now, before you plug this all together, grab your voltmeter... plug the little Eflite battery into the female socket, and check that the receiver plug is showing 7.4 volts, red wire should be POSITIVE. consult the diagram and find the problem if it isn't.


Now UNPLUG the Eflite battery, and plug the receiver plug into the battery slot of the receiver. When you plug the Eflite battery into the extension socket, your receiver and speed control should power up. Do NOT turn your speed control on when you power the receiver this way. IN fact, it's probably a good idea to move the ESC switch to an out of the way place where it can't be turned on by mistake.

Unplug the Eflite battery from the socket to recharge it (or just to turn the car off)

Oh... that extra half a servo lead left over... use it to make an adapter socket for your charger to charge the tiny eflite LiPO. Charge at 1/10 of an amp... it should only take a few minutes to top off after a run.

Here's the wiring diagram:
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Last edited by Trips; 03-16-2009 at 05:56 PM. Reason: updated circuit to reduce voltage input to receiver
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Old 03-14-2009, 05:42 PM   #54
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And here's a pic of it installed in the GenX. You can see just how small that Eflite battery is, hiding there next to the left front suspension arm.

IF you look carefully, you can see I added a switch to the circuit on the chassis. I did this primarily for the benefit of the turn marshals... if my car goes dead or breaks during a run, I wanted to make it easy for the marshal to turn the car off rather than have to pull the body and unplug the connection.

If you decide to add a switch to yours, the most logical place is in the BLACK wire going from the POSITIVE side of the Deans plug to the Socket for the EFLite battery. Anywhere between the Positive side of the Deans plug and the reciever plug will work. Don't pout the switch in the wire from the receiver plug to the NEGATIVE side of the Deans connector... if you put it there it will be useless.

Another thing you'll notice is the pair of battery bars I servo taped to the top of the SMC pack... the reason for this is so that if I need to run my NIMH packs for whatever reason, I can just pop the SMC pack out of the car and pop the NIMH in without having to re-wire the car. LiPO 1/12th's aren't allowed everywhere yet...
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Old 03-14-2009, 05:57 PM   #55
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Quote:
Originally Posted by Trips View Post
And here's a pic of it installed in the GenX. You can see just how small that Eflite battery is, hiding there next to the left front suspension arm.

IF you look carefully, you can see I added a switch to the circuit on the chassis. I did this primarily for the benefit of the turn marshals... if my car goes dead or breaks during a run, I wanted to make it easy for the marshal to turn the car off rather than have to pull the body and unplug the connection.

If you decide to add a switch to yours, the most logical place is in the BLACK wire going from the POSITIVE side of the Deans plug to the Socket for the EFLite battery. Anywhere between the Positive side of the Deans plug and the reciever plug will work. Don't pout the switch in the wire from the receiver plug to the NEGATIVE side of the Deans connector... if you put it there it will be useless.

Another thing you'll notice is the pair of battery bars I servo taped to the top of the SMC pack... the reason for this is so that if I need to run my NIMH packs for whatever reason, I can just pop the SMC pack out of the car and pop the NIMH in without having to re-wire the car. LiPO 1/12th's aren't allowed everywhere yet...
Looks good, sounds dangerous I'll wait for the official tekin solution, but I love your electrical engineering spirit
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Old 03-15-2009, 11:29 AM   #56
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I have some comments on this setup as the speedo manufacturer…

First we really do not like getting 8.4V from the receiver. It appears to work so far, but it is on the edge for us to deal with. We like 5V to 6V and we can deal with7V, but a full lipo supplying over 8V is a concern. A lot of people are using a 2s lipo for a receiver pack and it seems to be working, but it is not something we are in favor of.

Here is another solution that is easy, safe and works pretty good with the spec motors.

Just put a servo plug from the speedo battery post or the 1S lipo to the receiver. This gives the receiver the full voltage of the single cell lipo and adds a few tenths of voltage from a normal config. The BEC output in a normal setup is typically .3 to .5V less than the battery.

This setup does need our new 1S software ( not released yet) to ensure you have full throttle for the entire run. It works pretty good with the current software, except 189, with the slower motors. The harder you pull on the battery the sooner the throttle reductions kick in late in the run.

Leave the red wire in the receiver plug and turn the speedo switch on. The VC will work correctly and can be set for 3V in the hotwire. If you are willing to have 4v or less for the servo this may be the best setup overall in the end. Our favorite is still a booster that supplies 5V or 6V to the receiver.

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Old 03-15-2009, 06:23 PM   #57
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Jim, thanks for the information, I didn't hurt anything today running this setup, but I'm going to stop using this method before I DO hurt something...

I want to ask some things, probably easiest if I reply to portions of your post...

Quote:
Originally Posted by TeamTekin View Post
I have some comments on this setup as the speedo manufacturer…

First we really do not like getting 8.4V from the receiver. It appears to work so far, but it is on the edge for us to deal with. We like 5V to 6V and we can deal with7V, but a full lipo supplying over 8V is a concern. A lot of people are using a 2s lipo for a receiver pack and it seems to be working, but it is not something we are in favor of.
I still like the simplicity of this setup, but now that you've made me aware of the voltage concern, I was thinking it would be pretty simple to add two diodes in series to drop the voltage from 8.4 to the 6-6.4 range. Back in the early days of 1/12, we ran a pair of diodes in the wiring of our 6 cell cars to drop the voltage from 7.2 to something safe for the receiver... Each diode in series knocked about a volt off... We ran our 4 cell cars without diodes. Do you think I'd be reasonably safe doing this until the Novak booster is available? A booster is going to be my choice once I can actually get it.

Quote:
Originally Posted by TeamTekin View Post
Here is another solution that is easy, safe and works pretty good with the spec motors.

Just put a servo plug from the speedo battery post or the 1S lipo to the receiver. This gives the receiver the full voltage of the single cell lipo and adds a few tenths of voltage from a normal config. The BEC output in a normal setup is typically .3 to .5V less than the battery.

This setup does need our new 1S software ( not released yet) to ensure you have full throttle for the entire run. It works pretty good with the current software, except 189, with the slower motors. The harder you pull on the battery the sooner the throttle reductions kick in late in the run.
I actually tried this before I came up with the idea to add a little LiPO in series... I flashed my RS back to 1.80 firmware, re-calibrated it to the radio, and ran a lead right from the SMC LiPO to the receiver. What I noticed was that the power wasn't there even very early in the run... I especially noticed it when going from full throttle to partial throttle, then back to full... after the partial throttle, I couldn't get full throttle power again until after coming to a stop.

Quote:
Originally Posted by TeamTekin View Post
Leave the red wire in the receiver plug and turn the speedo switch on. The VC will work correctly and can be set for 3V in the hotwire. If you are willing to have 4v or less for the servo this may be the best setup overall in the end. Our favorite is still a booster that supplies 5V or 6V to the receiver.
This is where I probably went wrong in my test... I left the RS switch off the runs. Maybe I need to try again with the RS switched ON, but to be honest I really prefer to run 1.89 to 1.80

Like I said, I WILL be going with the booster once it's available. I'd really like to hear your opinion on the use of a couple of diodes to drop the 8.4 down into the 6.something range until then...

Thanks,
D
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Old 03-15-2009, 06:42 PM   #58
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I guess I'll do a quick report on how it went today...

I'm running a CRC GenX, with 4 cells and a Trinity Duo17.5 it hits the track at 830 grams. Definitely one of the lightest 4 cell NIMH cars I've seen at 360 Speedway, most guys still running 4 cells are in the high 800's or low 900 gram range.

With the SMC LiPO in place of the 4 cell NIMH, along iwth my tiny LiPO "booster cell" and the extra switch and wiring, the car today hit the scale at 872 grams. That was with the Trinity Duo 17.5 still in place. I borrowed an LRP Vector X11 13.5 turn for today, which is about 12 grams heavier than the Trinity Duo, so I was hitting the track at 684 grams. IF you recall my photo of the car a few posts back, I added a switch, and also some battery bars to the top of the SMC pack. I'm getting rid of the switch and battery bars, they add more grams than they're worth. As long as I'm unplugging the LiPO "booster cell" between runs to charge it, there's no need to have a switch there as well. I'll just plug it back in right before the run to turn the car on. Also, the switch and battery bars represent a bunch of extra solder joints in the car (more possible failure points than I really need in my car. IN fact I did have a few issues with a bad solder joint that killed a couple of runs for me today.

Performance... My fast laps today were EXACTLY the same as my fast lape last week with 4 cell NIMH and a 17.5, BUT the car was MUCH easier to drive consistently this weekend. My best run this week was THREE fulll laps faster than last week, and my best single lap that run was a 10.0... last weekend my best run was three laps slower, and I hit a few 9.9's in that run, but the consistency just wasn't there.

For anyone wondering, I ran the 1.89 firmware, max boost, timing ring on the LRP Vector 13.5 fully clockwise. Rollout 3..3" (76/46 gearing, 1.75 diameter tires)
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Old 03-15-2009, 06:48 PM   #59
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I would not recommend running a small LiPo with the bigger main pack. Once the small pack goes dead it's going to be pulled way down and ruin the cell.

Not the safest thing to do with the cells.
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Old 03-15-2009, 07:26 PM   #60
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Quote:
Originally Posted by Trips View Post
I guess I'll do a quick report on how it went today...

I'm running a CRC GenX, with 4 cells and a Trinity Duo17.5 it hits the track at 830 grams. Definitely one of the lightest 4 cell NIMH cars I've seen at 360 Speedway, most guys still running 4 cells are in the high 800's or low 900 gram range.

With the SMC LiPO in place of the 4 cell NIMH, along iwth my tiny LiPO "booster cell" and the extra switch and wiring, the car today hit the scale at 872 grams. That was with the Trinity Duo 17.5 still in place. I borrowed an LRP Vector X11 13.5 turn for today, which is about 12 grams heavier than the Trinity Duo, so I was hitting the track at 684 grams. IF you recall my photo of the car a few posts back, I added a switch, and also some battery bars to the top of the SMC pack. I'm getting rid of the switch and battery bars, they add more grams than they're worth. As long as I'm unplugging the LiPO "booster cell" between runs to charge it, there's no need to have a switch there as well. I'll just plug it back in right before the run to turn the car on. Also, the switch and battery bars represent a bunch of extra solder joints in the car (more possible failure points than I really need in my car. IN fact I did have a few issues with a bad solder joint that killed a couple of runs for me today.

Performance... My fast laps today were EXACTLY the same as my fast lape last week with 4 cell NIMH and a 17.5, BUT the car was MUCH easier to drive consistently this weekend. My best run this week was THREE fulll laps faster than last week, and my best single lap that run was a 10.0... last weekend my best run was three laps slower, and I hit a few 9.9's in that run, but the consistency just wasn't there.

For anyone wondering, I ran the 1.89 firmware, max boost, timing ring on the LRP Vector 13.5 fully clockwise. Rollout 3..3" (76/46 gearing, 1.75 diameter tires)
Your LRP motor is 12 grams heavier then your DUO... You must have the new DUO "light" series.
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