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R/C Tech Forums Thread Wiki: New Schumacher KF2
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Welcome to the KF2 Wiki!

Please feel free to add any Tips, Tricks, or anything that would be beneficial to the KF2 Family

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Tony Newland Gear Diff BuildTony Newland Gear Diff Build

Suggested Gearing

6.5
7.5
8.5
9.5
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13.5
17.5 I ran 69/31 at SRS Scottsdale Arizona and 72/30 at MHOR Aurora Co and Full Throttle ALB, NM RCM lockout worked excellent!


MIP pucks excellent upgrade! The new RCM lockout is an excellent piece as well! These options will greatly reduce weight throughout the drive line!

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Old 07-16-2015, 07:07 PM   #331
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What, if any can be done to make the KF2 more 17.5 friendly? The internal gear ratio is fairly close to my RB6 and when I use the same electronics and FDR between the two cars my KF2 does not keep up with my RB6 and runs much hotter (130deg vs 175deg). It also lacks off the line since I can't get enough rear traction, the tires spin like crazy. I tape in the battery up against the rear tranny halves to move it as far back as possible and I use the rear mount shocks.
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Old 07-16-2015, 08:56 PM   #332
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Move ESC by tranny to move weight back.
4 degrees anti squat
Run fan on motor
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Old 07-16-2015, 11:56 PM   #333
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Anybody got a pic of the preferred electronics layout with the low grip kit installed.
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Old 07-17-2015, 02:43 AM   #334
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Default KF2

Hi,
Hope this can help, this is what i use for my Kf2
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Old 07-17-2015, 09:05 AM   #335
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Seems like a good time to show this to you guys given the last post about layout and the one before that about traction issues.....

A while ago I pretty much concluded that this car was maybe not the best choice for medium grip clay surfaces and lower. The key factor being an optimal weight distribution simply could not be achieved without extensive modifications. I have been running a B5M at my local club and doing pretty well with it but I would much prefer to run the KF2. My B5M scales out at 36.75% Front / 63.25% Rear. As Tony Newland has observed before it seems that roughly 63-64% in the rear is the sweet spot for the type of surfaces we are targeting. My experiences support that view.

The best I could do with the KF2 in terms of weight distribution was 38.5% Front / 61.5% Rear. This was with rear and front arms reversed, low grip kit, shorty all the way back, shocks on the back. I think somebody else on this thread got it to 62% with a low profile servo up front, which is the best I am aware of. If someone else has done better please let me know.

So I had basically given up on the car until I noticed very recently that LRP had released a new "Super Shorty" battery that is extremely lightweight and compact at the expense of some capacity (2600 mAh). Here is a link for more info:

LRP Super Shorty

When I saw this I thought to myself, hmmmmmmm I wonder if one of these will give me enough space in the back of the KF2 to move my ESC back next to it in a similar way Tom Cockerill did at Motorama in 2014? It turns out that the answer is yes...

New Schumacher KF2-img_0383.jpg

After I measured it out and confirmed it would all fit my goals were:
  • Achieve at least 37% Front / 63% Rear weight distribution
  • Relocate almost all weight saved to remain between the axles
  • Stay under 1600g total (in full race trim)

Item two in the above list seems to be important from what I have learned so I tried to closely adhere to that. I mean you could just start hanging lead off the back of the car to get to 37/63 but it probably wouldn't perform well. The "where" of weight is perhaps even more important than the "how much". Here is where I did end up adding some weight:
  • 28g Under the ESC to balance out with the battery
  • 14g tucked into the diff housing right in front of the diff but behind the anti-squat insert
  • 12g attached to the back of the housing using the two screws that hold the upper plastic cover in place

Here is a summary of the rest of the setup/part changes:
  • Optional CF chassis
  • Cougar KR CVA driveshafts (U4069) (Allows you to run rear arms reversed with shortest wheelbase and no limiters in shocks needed to prevent pop-outs)
  • 44g Savox 1251MG low profile servo (This saved 16g up front and made a big difference)
  • Low Grip configuration
  • Rear mounted shock kit
  • Front and rear arms reversed
  • Rear hubs all the way forward

I have also attached a setup sheet to this post for those looking to try this out.

Now after all this the car currently scales at 36.6 % Front / 63.4% Rear, which is better than my B5M!
Total weight is about 1565g, which includes all the stock bracing, side pods and slipper etc. If you are running stock I know you could get this down close to min weight with little difficulty.

And wouldn't you know that on the track the car feels very similar to my B5M? I have about 4 packs on the car and my times are about the same as they were with the B5M. However, I feel this car has more potential because of the amount of steering and the corner speed it can maintain. I am not fully adjusted to this yet in terms of driving style so I expect to start getting faster once I can start taking advantage of it with some practice. I also expect to see our track start moving towards even more grip as time goes on so as the grip increases so will the happiness of the KF2.

What I have outlined here is not all roses of course. I would imagine not everyone is going to be able to use one of these LRP Super Shorty batteries. We run 5 minute heats and typically run 7.5/8.5 turn motors on our track. If you run 10 minute mains or are bolting in 4.5t motors this battery might not work. It is more than enough for my application and I do not experience any sag or noticeable loss of punch. Another thing I would like to see removed is the 12g weight hanging on the back. I have not measured the car without it there but it I am calculating it would put me at about 63% even on the rear. I am going to try driving it without it as I expect that it may actually hurt on some of the tighter turns on entry (pendulum effect). And also keep in mind that I could easily get into the 65% rear weight range on the B5M with some optional parts and the numbers I have posted here do not reflect the limits of the B5M in any way in this regard.

That being said does anyone want to buy a used B5M?
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New Schumacher KF2-kf2_setup_clubhouse_7_16_2015.jpg  
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Last edited by motorcitymatt; 07-17-2015 at 01:22 PM. Reason: Typo
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Old 07-17-2015, 09:21 AM   #336
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Thanks for the write up, Matt!

Would a half of a saddle pack work in place of the super shorty? It appears to be roughly the same size. I'm not familiar with the mechanics of batteries, but half of a 2s 5800mah 100c saddle would be 1s 2900 and 50c, would it not?
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Old 07-17-2015, 09:32 AM   #337
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Unfortunately I do not think that will work. Saddle packs are wired in series to achieve 2S (7.4v) at the ESC. If you wired one half of the saddle pack you would only have 1S (3.7v) fed to the ESC.

There may be saddle packs wired in parallel out there where your idea would work but I am not aware of any. Have any of you seen parallel saddle packs?
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Old 07-17-2015, 12:22 PM   #338
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Excellent work Matt..! Thank you for the detail.. !!


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Old 07-22-2015, 07:32 AM   #339
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Just an FYI for you guys, the Savox 1251MG low profile servo I put in the KF2 to pull some weight off the front lasted about three packs

I am not sure if I got a bad one or if they are just not up to the demands of off-road. I noticed it had completely frozen up right after I came off a jump a little too nose-down favoring one front wheel. That wheel took most of the blow on the landing.

Anyway, if there are recommendations for a more robust low profile or lightweight servo I would love to hear them.

And FWIW, I run/have run the Savox 1258TG and it has been bulletproof. I do not mean to question the durability/reliability of Savox products. I was just going on the the company's claim on their website for the product: "Ideal as a steering servo for 1/10 surface applications"
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Old 07-22-2015, 07:42 AM   #340
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I'm running sanwa s6070 in my kf2. I'll probably be dropping in a R1 shorty servo next

I'm awaiting lrp super shortly to try the same.
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Old 07-22-2015, 07:50 AM   #341
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Quote:
Originally Posted by motorcitymatt View Post
Just an FYI for you guys, the Savox 1251MG low profile servo I put in the KF2 to pull some weight off the front lasted about three packs

I am not sure if I got a bad one or if they are just not up to the demands of off-road. I noticed it had completely frozen up right after I came off a jump a little too nose-down favoring one front wheel. That wheel took most of the blow on the landing.

Anyway, if there are recommendations for a more robust low profile or lightweight servo I would love to hear them.

And FWIW, I run/have run the Savox 1258TG and it has been bulletproof. I do not mean to question the durability/reliability of Savox products. I was just going on the the company's claim on their website for the product: "Ideal as a steering servo for 1/10 surface applications"
I actually just stripped the gears in a 1251 in one of my KF's. I'm running a 1257TG in my other one and its been bulletproof and been through about 5 different buggies.
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Old 07-22-2015, 07:50 AM   #342
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When I ran a shorty I used with the plastic arm for safety....

These are good
http://prime-hobby.com/index.php?rou...product_id=326
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Old 07-22-2015, 07:55 AM   #343
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Quote:
Originally Posted by hanulec View Post
I'm running sanwa s6070 in my kf2.
Any durability issues with it? Looking at the specs and pictures it looks almost identical to the Savox 1251, maybe a re-brand.

Can you post a link to the R1 servo you are referring to?
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Old 07-22-2015, 08:07 AM   #344
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Quote:
Originally Posted by Tony Newland View Post
When I ran a shorty I used with the plastic arm for safety....
Good point. I was using an aluminum CoreRC servo arm. After hearing of all the broken plastic ones I never looked back after replacing the plastic.
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Old 07-22-2015, 06:09 PM   #345
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I havent heard of any shorty lasting super long in offroad... theyre mainly designed for onroad
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