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  1. #101
    Community Moderators Foxy's Avatar
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    RE: HPI Mini Recon


    ORIGINAL: srt10

    ORIGINAL: Foxy

    ORIGINAL: srt10

    ORIGINAL: stevenkelby

    I forgot to mention gearing is very important too, sometimes a high kv motor won't be able to get up into it's high revs where it makes power because the cars gearing is too long for it to pull without a ton more voltage like a 4cell pack. The whole thing starts getting expensive especially when the driveline melts from all the extra power as the other guys mentioned.
    Actually a brushless motor has most of its torque at low rpms, or right off the line
    they don't need to build rpms like a 2 stroke to make hp
    that's why brushless pull harder during a start than nitro
    and you can gear the motor to a heat range
    and they will pull excess amps not volts if geared to high for speed, the amps is what heats them up...
    and the more amps a motor pulls the more HP it makes!
    A brushless motor does not have most of its torque anywhere, it's completely linear. That's its advantage over nitro. The WATTS is what heats motors up and HP has nothing to do with amps. Watts to HP is a straight conversion (pretty much). If you want a comparison, volts is like how many legs the horse has, amps is how muscular (strong) the horse is, and watts is the actual power the horse puts to the ground (hp) by combining the other two.
    well actually, amps x volts = watts
    pull to many amps through a motor, more than its rated for it heats up, same as to many watts... so its really the same, kinda
    the best setup for big FE is more Volts and less KV = less amps = less heat... more KV less Volts = more heat ... same watt output.... hmmmmmmm
    and again Amps X Volts = Watts = HP
    just worded different but the same conclusion.. HP
    you can't have Watts without Amps
    14.8V x 50.4 Amps = 746 Watts = 1 HP
    and I get ya on the Linear power from brushless motors.. and most brushless trucks with big power can do standing back flips... not much rpm needed
    No, not 'the same thing but worded differently'. I'm not trying to be condescending on purpose, simply making sure the correct info is on the forum. You made an incorrect statement which I corrected.

    You stated amps cause heat which is incorrect. Amps * volts causes heat. If amps caused heat, then heat wouldn't increase with voltage. See why it's wrong to say amps cause heat?

    Also, your example is still wrong. You can't 'pull more amps through a motor than it's rated for'. The motor draws as many amps as it needs, and the amount of watts changes with different voltages.

    A motor may state it pulls 100 amps at max load. That doesn't change with voltage. Let's say we have a 5000kv motor which pulls 100 amps at full load. I use a 7.4v 2s battery. So, I can now tell how many watts my motor is pulling, 7.4*100=740W. I now replace it with an 11.1 3s battery. The motor STILL pulls 100 amps at full load, but spins faster and pulls more watts due to the higher voltage. That's why adding a cell adds a lot of heat usually. This is the important message I wanted to get across in correction to 'amps=heat'.

    If you still think we're saying the same thing, fine, I'm not going to labour the point.
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  2. #102

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    RE: HPI Mini Recon

    ORIGINAL: Foxy


    ORIGINAL: srt10

    ORIGINAL: Foxy

    ORIGINAL: srt10

    ORIGINAL: stevenkelby

    I forgot to mention gearing is very important too, sometimes a high kv motor won't be able to get up into it's high revs where it makes power because the cars gearing is too long for it to pull without a ton more voltage like a 4cell pack. The whole thing starts getting expensive especially when the driveline melts from all the extra power as the other guys mentioned.
    Actually a brushless motor has most of its torque at low rpms, or right off the line
    they don't need to build rpms like a 2 stroke to make hp
    that's why brushless pull harder during a start than nitro
    and you can gear the motor to a heat range
    and they will pull excess amps not volts if geared to high for speed, the amps is what heats them up...
    and the more amps a motor pulls the more HP it makes!
    A brushless motor does not have most of its torque anywhere, it's completely linear. That's its advantage over nitro. The WATTS is what heats motors up and HP has nothing to do with amps. Watts to HP is a straight conversion (pretty much). If you want a comparison, volts is like how many legs the horse has, amps is how muscular (strong) the horse is, and watts is the actual power the horse puts to the ground (hp) by combining the other two.
    well actually, amps x volts = watts
    pull to many amps through a motor, more than its rated for it heats up, same as to many watts... so its really the same, kinda
    the best setup for big FE is more Volts and less KV = less amps = less heat... more KV less Volts = more heat ... same watt output.... hmmmmmmm
    and again Amps X Volts = Watts = HP
    just worded different but the same conclusion.. HP
    you can't have Watts without Amps
    14.8V x 50.4 Amps = 746 Watts = 1 HP
    and I get ya on the Linear power from brushless motors.. and most brushless trucks with big power can do standing back flips... not much rpm needed
    No, not 'the same thing but worded differently'. I'm not trying to be condescending on purpose, simply making sure the correct info is on the forum. You made an incorrect statement which I corrected.

    You stated amps cause heat which is incorrect. Amps * volts causes heat. If amps caused heat, then heat wouldn't increase with voltage. See why it's wrong to say amps cause heat?

    Also, your example is still wrong. You can't 'pull more amps through a motor than it's rated for'. The motor draws as many amps as it needs, and the amount of watts changes with different voltages.

    A motor may state it pulls 100 amps at max load. That doesn't change with voltage. Let's say we have a 5000kv motor which pulls 100 amps at full load. I use a 7.4v 2s battery. So, I can now tell how many watts my motor is pulling, 7.4*100=740W. I now replace it with an 11.1 3s battery. The motor STILL pulls 100 amps at full load, but spins faster and pulls more watts due to the higher voltage. That's why adding a cell adds a lot of heat usually. This is the important message I wanted to get across in correction to 'amps=heat'.

    If you still think we're saying the same thing, fine, I'm not going to labour the point.
    Ok, a couple things Foxy.. I think thigs are getting lost in the comments on the net...
    example lets say
    30,000rpm 4000watt system
    1) 1351kv motor on 6s = *30,000rpms .... 180amsp x 8s = 4000watts
    2) 675kv on 12s = *30,000rpms .............. 90amps x 12s = 4000watts
    #1 will generate more heat because it is pulling more amps to get same rpms and the same watts
    both rated to 4000watts and same size motors
    thats more what I'm talking towards Foxy.. same watts, but more amps though one of the motors

    I agree if you put more volts to the same motor on the same gearing it will pull more amps and make more watts and heat up very fast
    and in the real world, putting more amps to the same system will cause the motor to pull more amps and have higher amps spikes
    but gear correctly like I said to begin with will work, and also keep things running in the proper heat range
    more volts + lower gearing = lower temps (usually)

    and yes a motor will only pull the amps needed to run
    that has nothing to do with pulling more amps than rated
    when we run FE boats with to big of a prop we can pull more amps than the motor is rated for specially with more volts through the system
    same I think for esc failures.. to many amps being pulled through them = magic smoke
    big reason the spartan had constant failing motors on 6s (also escs), the motors were pulling more amps than it was rated for

    but back to your 100amp motor.. YES putting more volts through that motor with the same 100amp draw does make more watts and heat up to
    but I get what your saying...
    so you saying to many watts = more heat, is correct
    and me saying pulling to many amps = more heat, is correct to
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  3. #103
    Community Moderators Foxy's Avatar
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    RE: HPI Mini Recon

    I don't disagree with anything you've written, only the way you phrased it. It's clear you know what you're talking about, just your examples were a little off. What I'm saying is real simple: A motor pulls a certain number of amps, regardless how many cells you are using or whether you are overdriving it, even if overdriving it, it still pulls the same number of amps regardless how many cells. With a 2s battery it doesn't get hot. With a 3s battery it does. Of course if you are overdriving it, it's gonna get hot no matter what type of battery you use). Point is; it still pulled the same amount of amps, the amps are not what is making it hot. See what I mean?

    If you still disagree, we can continue this by PM.

    PS. You know what this discussion highlights for me? It highlights the fact that to use amps as the defining unit for the capacity of speed controllers and motors is backward. Limits would be much better expressed in watts (and amps if necessary), don't you think?
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  4. #104
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    RE: HPI Mini Recon

    I can't believe the nerve of some people getting threads so far off topic...

    Sooo anyways lets get this back on topic

    Got the 5200kv BL motor in turns out what I read somewhere else was true the stock mounting holes are a teeny bit too far out on the motor mount plate. Had to dremel the holes a teeny bit cause the HW's motors holes are a lil closer to the shaft. When I say a teeny bit I mean I almost can't even see the difference with the naked eye level of modification. Also had to find some smaller screws cause the brushed HPI motor used screws that were way too thick. Outside that the motor meshed up fine, and seems to run fine. Can't test it out till maybe Tuesday outside though (weather permitting).
    With great speed comes greater repair bills.
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  5. #105
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    RE: HPI Mini Recon

    Simple way to explane electricity, its like water in a hose, the pressure of the water in the hose is the voltage, the flow is current in watts/amps or whatever.

    volts allows electricity to force its way through a restriction (ohms) and amps is how much electricity can flow.

    Heat is a direct relationship to amps, HOWEVER when talking about a motor you have to factor in EFFICIENTCY, the ability to do work with the amount of electricity (or heat) is applied. so figure a high efficientcy motor is 97%. so 97% of the energy applied is work (the motor spins) and the remaining 3% is heat, friction and sound. anytime you restrict a motor it makes the voltage drop and draw (amps) go right up. a special effect of a electric motor is that a spinning motor creates COUNTER VOLTAGE... countervoltage reduces the amount of volts/draw is required to make it do work since in a way its powering itself- when you add friction to this motor it HEATS UP. why? remember efficiency??? it was 97% running free with no load, now figure its at 50% so now half of all that electricty you put in is turning to heat!

    this is why high KV motors more often than not heat up more compaired to low KV motors. high KV motors spin much faster and generate more friction both in the drive train but also the wind and the terrain, this slows this motor down driving the effiecientcy down making the amount of heat generated higher.

    geddit?

    on topic i found out something... the outrunner i used on my rc18 is 600watts... a mild/hot 4700kv motor for a 1/10 is around 440.... i LOVE outrunners, so much power in a little package, its going into my digger once i get it!
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  6. #106

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    RE: HPI Mini Recon

    I've never learn so much within these 2 pages. Very good information
    How fast is MR out of the box? I tried to look it up but i cant find it.

  7. #107

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    RE: HPI Mini Recon


    ORIGINAL: dbigfoot111

    I've never learn so much within these 2 pages. Very good information
    How fast is MR out of the box? I tried to look it up but i cant find it.
    Agreed, good discussion

    I read it does 20mph out the box.

  8. #108
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    RE: HPI Mini Recon

    just about all 1/18 or 1/16 are 15 to 20mph. off the batt they do scoot around pretty quick for what they are, fun out of the box not doggy at all.

    however you get one of these going above 40mph it starts to turn into a handfull.
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  9. #109
    SyCo_VeNoM's Avatar
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    RE: HPI Mini Recon


    ORIGINAL: The_Shark

    Simple way to explane electricity, its like water in a hose, the pressure of the water in the hose is the voltage, the flow is current in watts/amps or whatever.

    volts allows electricity to force its way through a restriction (ohms) and amps is how much electricity can flow.

    Heat is a direct relationship to amps, HOWEVER when talking about a motor you have to factor in EFFICIENTCY, the ability to do work with the amount of electricity (or heat) is applied. so figure a high efficientcy motor is 97%. so 97% of the energy applied is work (the motor spins) and the remaining 3% is heat, friction and sound. anytime you restrict a motor it makes the voltage drop and draw (amps) go right up. a special effect of a electric motor is that a spinning motor creates COUNTER VOLTAGE... countervoltage reduces the amount of volts/draw is required to make it do work since in a way its powering itself- when you add friction to this motor it HEATS UP. why? remember efficiency??? it was 97% running free with no load, now figure its at 50% so now half of all that electricty you put in is turning to heat!

    this is why high KV motors more often than not heat up more compaired to low KV motors. high KV motors spin much faster and generate more friction both in the drive train but also the wind and the terrain, this slows this motor down driving the effiecientcy down making the amount of heat generated higher.

    geddit?

    on topic i found out something... the outrunner i used on my rc18 is 600watts... a mild/hot 4700kv motor for a 1/10 is around 440.... i LOVE outrunners, so much power in a little package, its going into my digger once i get it!
    lols sounds like the way my 1st electronics teacher in college described electricity. After he was done he said something like NOW YOU CAN BE A ELECTRIC TECHNICIAN OR A PLUMBER YOUR CHOICE SEEING ITS BASICALLY THE SAME PRINCIPLES
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  10. #110
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    RE: HPI Mini Recon

    i learned what i know from auto school in addition to shocking the crap out of myself and acidentally starting things on fire.

    im one of those students that wants to know more about a subject, not just what i NEED to know
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  11. #111
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    RE: HPI Mini Recon


    ORIGINAL: The_Shark

    i learned what i know from auto school in addition to shocking the crap out of myself and acidentally starting things on fire.

    im one of those students that wants to know more about a subject, not just what i NEED to know
    Was the same way. So many times have I blown things up things from experimentation in the name of science
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  12. #112

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    RE: HPI Mini Recon

    It's kind of weird how this little truck is getting so much airplay on the forums. It's basically the same thing as the HPI Brama 18b that was released a year or two ago. No one really paid any attention to the buggy, but it sounds like there are a few takers for the Recon. That's cool though, hopefully I can use some of the Recon parts for my Brama, which has been a fun little buggy.

  13. #113
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    RE: HPI Mini Recon


    ORIGINAL: Rody63

    It's kind of weird how this little truck is getting so much airplay on the forums. It's basically the same thing as the HPI Brama 18b that was released a year or two ago. No one really paid any attention to the buggy, but it sounds like there are a few takers for the Recon. That's cool though, hopefully I can use some of the Recon parts for my Brama, which has been a fun little buggy.
    the brama 18b was cursed due to its name
    oddly the exquisite failure of a RC that doomed its name the Brama 10B is not discontinued even though it arguably is one of the worst RC's(durability, upgrades, and parts support wise) on the market(counting the Hong Kong knockoffs)...
    With great speed comes greater repair bills.
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  14. #114
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    RE: HPI Mini Recon

    man this thing can take a hit! misjudged a full speed turn entry and smacked a curb head on at top speed, flew about 20 feet before carwheeling. flipped it over and took off.

    NO damage has been done to this thing so far, and thats saying alot for a brushless setup. even the diffs are still silky smooth with 3s outrunner full throttle bursts!

    the handling is SWEET, just a tad bit of understeer and thats welcome due to 1/18 tracking issues.

    handles much better than my rc18t i had, the suspension actually does work and you can see it lean and dive into turns and bumps.

    i think im going to leave that monster motor out of there, i know it will just eat this thing alive.
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    RE: HPI Mini Recon

    Does anyone know the maximum dimensions of the battery compartment? I'm trying find a lipo that will fit. 

    If anyone has a link to one they know will work, that would also be greatly appreciated.

  16. #116
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    RE: HPI Mini Recon

    using these myself right now http://www.hobbypartz.com/77p-1300mah-2s1p-74-15c.html
    had to dremel the battery compartment side wall a teeny bit to make it like a fraction of a mm wider to have them sit nice. The dremeling was so minor you can't even really tell where I did it unless you look closely
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    RE: HPI Mini Recon

    That is a tiny battery compared to what I was looking at. Is there plenty of room, length wise, to go?
    I was looking at this site which claims this 2250mah battery will fit. While I would never pay that price, I was using the size they give (99mm x 34mm x 16mm)as a reference.
    http://www.maxamps.com/proddetail.ph...t-Pack&cat=315
    So I was then looking at this battery, which is 93x30x14:
    Is this way to long?

  18. #118
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    RE: HPI Mini Recon


    ORIGINAL: Blitz813

    That is a tiny battery compared to what I was looking at. Is there plenty of room, length wise, to go?*
    *
    I was looking at this site which claims this 2250mah battery will fit. While I would never pay that price, I was using the size they give (99mm x 34mm x 16mm)*as a reference.
    http://www.maxamps.com/proddetail.ph...t-Pack&cat=315
    *
    So I was then looking at this battery, which is 93x30x14:
    *
    Is this way to long?
    the HK battery should fit (the battery compartment is exactly 100mm's long just pulled out my micrometer) only issue I could possibly see is the battery wires look a tad thick, an might not bend in the space needed
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  19. #119
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    RE: HPI Mini Recon

    a micky-mouse fix is to use long screws for the hold down studs, and then put the battery in there at an angle. and adjust the screws so you can put some pressure on the battery.

    im running a 3s 100mm long battery this way.
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  20. #120

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    RE: HPI Mini Recon

    Thanks for all the info. I am going to try my luck with the Turnigy.

  21. #121

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    RE: HPI Mini Recon


    ORIGINAL: The_Shark

    a micky-mouse fix is to use long screws for the hold down studs, and then put the battery in there at an angle. and adjust the screws so you can put some pressure on the battery.

    im running a 3s 100mm long battery this way.
    What mAh are you using?

    I have these 2 on order, 2 and 3 cell 1800mAh:

    http://www.hobbypartz.com/98p-25c-1800-2s1p.html

    http://www.hobbypartz.com/98p-25c-1800-3s1p.html

    Both are 90mm long and 30mm wide, 17 and 25mm high respectively. Should fit fine I hope.

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    RE: HPI Mini Recon

    Does anyone experience a loud buzzing from this car when not in motion?

  23. #123
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    RE: HPI Mini Recon


    ORIGINAL: Blitz813

    Does anyone experience a loud buzzing from this car when not in motion?
    is it the servo? I've noticed some servos can be quite loud try turning the wheel a teeny bit to see if it goes away
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    RE: HPI Mini Recon

    Yeah I believe its the servo. Just hope it isn't going bad. I can live with the noise, but it concerns me.

  25. #125
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    RE: HPI Mini Recon

    mini servos are always chattery untill you go with a high grade digital flight servo.

    also forgot to note, hobbyflight ESC work great for a brushless setup in these, they fit like a bug in the rug
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