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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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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 07-30-2015, 07:16 AM   #361
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Pic on schumacher Facebook page, I'm sceptical on low grip.
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Old 07-31-2015, 08:44 AM   #362
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I guess it depends on what you mean by "low grip". I think this might mean different things to different people depending on what surfaces you typically run on. To someone here in the U.S. low grip means rooster tails on loose dirt but in the U.K. it might mean wet and/or sandy astroturf.

Schumacher is specifically claiming dirt surfaces on their product page saying the kit addresses: " low and medium traction conditions such as dirt..." This is obviously good news. The layout looks very close to that of the YZ-2 with the motor maybe a little more forward. The owner of our track just started running a YZ-2 in favor of his RB6 and he adores it. With this kit for the KF2 I am hoping it puts it right there with it.

Even if I don't end up running this car as my main buggy I am still thankful for the way it has forced me to learn about setup and vehicle dynamics. Definitely trial by fire. My recent experiment with using the LRP super shorty and moving the ESC back has taught me that the F/R weight ratio is only part of the equation. The car right now is very similar to my B5M in terms of side bite and lateral grip and handling (with way more steering) but it still doesn't have the forward bite, even with 4 degrees of anti-squat running identical tires (swapped over). I get too much wheel spin and if I loosen the slipper to compensate then I'm unable to clear jumps well so it is tough. This is probably why some people on this thread have felt the car feels a little sluggish. I thought some of this might be due to the belt vs gear drive and heavier weight of the car but I think it is probably the traction. If you watch some of the videos from the EOS races with Michael Orlowski driving against other world class pros on carpet you will not notice any problems with sluggishness! In fact, in the race I watched he was clearly the fastest car on the track but Lee Martin just has robotic consistency.

I took the motor/trans pod assembly off my car in preparation for the new kit and weighed it. (See attached image). It comes in at 290g. The shorty lipo I have been using weighs about 205g. So by swapping these two things in the layout you are basically shifting around 85g more towards the rear of the car. The upper CF brace seen in the kit is replacing the aluminum side stiffeners from what I can tell so I will consider those to be a wash. My guess is that this change will put the car well into the 62% rear weight range and maybe just get to 63% depending on wheelbase configuration. But now we have the added flexibility of running a lighter battery to further reduce the weight in the front and this will be extremely useful. Some of the batteries referenced on Schumacher's page for the kit are about 155g. That should allow the rear to see even up to 64%. As a bonus the car should only weigh about 1515-1530g with a battery like this coupled with the CF chassis in the kit. This should make stock people happy.

But the dynamics of the motor and the forces it exerts on the chassis during acceleration based on its position in the car are really what this kit is bringing to the table. My car with a a similar weight distribution to what this kit provides with lots of anti-squat still lacks the forward bite compared to other MM cars on our track surface. With the motor further back like this the vertical component of the force (downward) produced by the motor
during acceleration is going to act on the chassis much further away from the center of mass (towards the rear) than it does with the existing low-grip position. In the low grip position the motor appears to sit very close to where the center of mass probably is on the car. So then you accelerate the downward force the chassis experiences would be like if you put your finger on top of the motor and pushed down. The whole car sits down a little because the motor is close to the center of the car. But now with the motor much further back the force should make the car sit down more during acceleration. And with the added weight in the rear it will make the effect even more pronounced. You should also be able to have more control over the pitch of the car in the air with this change. Equal throttle input will result in more pitch change than before.

It is worth mentioning that the current trend in the B5M community is to use a 3-gear transmission on higher traction surfaces. This is because the motor is mounted in reverse and spins clockwise instead of counter-clockwise. This makes the front of the car pitch forward during acceleration instead of rearward and helps keep the car flatter on power in the turns, which adds steering. But you end up giving up some forward bite and most of the cars I have seen run extra weight in the rear to compensate.

So the B5M people are trying to get corner speed by sacrificing rear grip with the 3-gear and we are trying to do the exact opposite with this kit for the KF2. Assuming this kit works well I think we are in a much better position for the future as tracks in the U.S. seem to be moving towards higher grip as a general trend. If the grip comes up just move the motor forward to keep the car flatter. This is a much more elegant design solution than turning the motor around and completely changing the vehicle dynamics IMO. And never mind you have to remember to use brake to pitch the car up in the air instead of throttle. That might be fine for Ryan Maefield but for people like me it is a nuisance.

I can't wait to try this kit out.....
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Old 07-31-2015, 12:01 PM   #363
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Matt, great write up!

I've got my upgrade kit on order along with a Fantom low-pro shorty battery. I may try it without the front stiffener to further increase the rearward weight component and add some flex.

My chief complaint along with your traction issue is that the KF2 in 17.5 doesn't preform as well as my RB6 using the same equipment or other geared (not belt driven) cars. I don't get the punch because of the traction issue, but it also lacks the top speed and runs much hotter than my RB6. I'm hoping the mid motor option gains traction, but also it gains top speed due to a reduction in rotating mass from a smaller belt.

Orlowski during EOS was running a modified motor. It's hard to compare mod to stock. If you don't like the top speed, drop in a faster motor.

For the price of the option kit, I would have rather seen a geared mid motor option than a shorter belt. I don't think this would have been too difficult to pull off with a redesigned upper tranny half that borrows the motor mount, adds a couple idler gears, and a redesigned diff gear and top shaft.
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Old 07-31-2015, 01:20 PM   #364
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Quote:
Originally Posted by motorcitymatt View Post
I guess it depends [...]
I can't wait to try this kit out.....
GREAT write-up, thanks.
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Old 07-31-2015, 02:12 PM   #365
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How tight is your belt? Mine is super loose....
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Old 07-31-2015, 02:53 PM   #366
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Mine is super loose....
Not loose. I thought you didn't want to run it loose.
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Old 07-31-2015, 05:57 PM   #367
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Not loose. I thought you didn't want to run it loose.
Make it nearly fall off if the track is slick
On wed night for the stock buggy main no one swept... Everyone was crying about their epic failures .... And that loose belt gave me an advantage over the other cars...
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Old 07-31-2015, 08:09 PM   #368
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Quote:
Originally Posted by Jpdanger View Post
Matt, great write up!
Thanks. Probably a little TL;DR but if it helps anyone else or gets a good discussion going then great.

Quote:
Originally Posted by Jpdanger View Post
I've got my upgrade kit on order along with a Fantom low-pro shorty battery. I may try it without the front stiffener to further increase the rearward weight component and add some flex.
I personally wouldn't run this new kit without the top brace. With the motor/trans assembly so far back the chassis now has a lot of space without additional reinforcement. It might be too much flex, making the car inconsistent. It looks like they even added a cross brace that doubles as a lipo holder to stiffen up the car laterally and reduce the torsional flex.

Quote:
Originally Posted by Jpdanger View Post
My chief complaint along with your traction issue is that the KF2 in 17.5 doesn't preform as well as my RB6 using the same equipment or other geared (not belt driven) cars. I don't get the punch because of the traction issue, but it also lacks the top speed and runs much hotter than my RB6.
I have done some testing with identical electronics/motor and similar gearing in my B5M and haven't noticed any significant differences in top end or motor temps after a run. Do you have better airflow over the motor on the RB6?

Quote:
Originally Posted by Jpdanger View Post
Orlowski during EOS was running a modified motor. It's hard to compare mod to stock. If you don't like the top speed, drop in a faster motor.
I guess my point there was that he wasn't lacking traction or at any disadvantage to the other cars due to the chassis vs the competition. If there is enough rear grip / forward bite, look out.

Quote:
Originally Posted by Jpdanger View Post
For the price of the option kit, I would have rather seen a geared mid motor option than a shorter belt. I don't think this would have been too difficult to pull off with a redesigned upper tranny half that borrows the motor mount, adds a couple idler gears, and a redesigned diff gear and top shaft.
Assuming it works well I think what they did makes the most sense for the car. The bulk of the cost in the kit lies in the carbon fiber chassis and upper brace. This kit makes use of most of the existing drivetrain parts minus the rear upper brace and the belt. Going to a geared tranny would really turn it into a whole different animal and go against the ethos of the design IMO.

But hey, if you want to spend another $80 over this kit you can have a geared transmission and the rest of an SV2 around it too!
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Old 07-31-2015, 08:18 PM   #369
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Originally Posted by hanulec View Post
Make it nearly fall off if the track is slick
So you are using the tension as a tuning option to add some slack to the drivetrain? Are you doing that with or without a slipper eliminator?

FWIW, I try to run mine as tight as I can until it starts to significantly slow down/add drag to the drivetrain when I spin it freely without a motor installed. This has always been more than enough to prevent the belt from jumping teeth on the pulleys.

This new kit will take one of the tensioners out of the picture, which should free things up even more.
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Old 07-31-2015, 11:43 PM   #370
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I always try and run my belts as loose as possible without them slipping, otherwise you create more drag. Try gently turning the belt around its own axis through 90 degrees with one finger, you should feel a point that it becomes tighter without using much force. This I find is a good starting point for belt tension, if it turns more than 90 degrees probably too loose and could slip, less and too tight.
You'll be surprised how loose you can run belts!
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Old 08-01-2015, 12:28 AM   #371
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Originally Posted by motorcitymatt View Post
I guess it depends on what you mean by "low grip". I think this might mean different things to different people depending on what surfaces you typically run on. To someone here in the U.S. low grip means rooster tails on loose dirt but in the U.K. it might mean wet and/or sandy astroturf.

Schumacher is specifically claiming dirt surfaces on their product page saying the kit addresses: " low and medium traction conditions such as dirt..." This is obviously good news. The layout looks very close to that of the YZ-2 with the motor maybe a little more forward. The owner of our track just started running a YZ-2 in favor of his RB6 and he adores it. With this kit for the KF2 I am hoping it puts it right there with it.

Even if I don't end up running this car as my main buggy I am still thankful for the way it has forced me to learn about setup and vehicle dynamics. Definitely trial by fire. My recent experiment with using the LRP super shorty and moving the ESC back has taught me that the F/R weight ratio is only part of the equation. The car right now is very similar to my B5M in terms of side bite and lateral grip and handling (with way more steering) but it still doesn't have the forward bite, even with 4 degrees of anti-squat running identical tires (swapped over). I get too much wheel spin and if I loosen the slipper to compensate then I'm unable to clear jumps well so it is tough. This is probably why some people on this thread have felt the car feels a little sluggish. I thought some of this might be due to the belt vs gear drive and heavier weight of the car but I think it is probably the traction. If you watch some of the videos from the EOS races with Michael Orlowski driving against other world class pros on carpet you will not notice any problems with sluggishness! In fact, in the race I watched he was clearly the fastest car on the track but Lee Martin just has robotic consistency.

I took the motor/trans pod assembly off my car in preparation for the new kit and weighed it. (See attached image). It comes in at 290g. The shorty lipo I have been using weighs about 205g. So by swapping these two things in the layout you are basically shifting around 85g more towards the rear of the car. The upper CF brace seen in the kit is replacing the aluminum side stiffeners from what I can tell so I will consider those to be a wash. My guess is that this change will put the car well into the 62% rear weight range and maybe just get to 63% depending on wheelbase configuration. But now we have the added flexibility of running a lighter battery to further reduce the weight in the front and this will be extremely useful. Some of the batteries referenced on Schumacher's page for the kit are about 155g. That should allow the rear to see even up to 64%. As a bonus the car should only weigh about 1515-1530g with a battery like this coupled with the CF chassis in the kit. This should make stock people happy.

But the dynamics of the motor and the forces it exerts on the chassis during acceleration based on its position in the car are really what this kit is bringing to the table. My car with a a similar weight distribution to what this kit provides with lots of anti-squat still lacks the forward bite compared to other MM cars on our track surface. With the motor further back like this the vertical component of the force (downward) produced by the motor
during acceleration is going to act on the chassis much further away from the center of mass (towards the rear) than it does with the existing low-grip position. In the low grip position the motor appears to sit very close to where the center of mass probably is on the car. So then you accelerate the downward force the chassis experiences would be like if you put your finger on top of the motor and pushed down. The whole car sits down a little because the motor is close to the center of the car. But now with the motor much further back the force should make the car sit down more during acceleration. And with the added weight in the rear it will make the effect even more pronounced. You should also be able to have more control over the pitch of the car in the air with this change. Equal throttle input will result in more pitch change than before.

It is worth mentioning that the current trend in the B5M community is to use a 3-gear transmission on higher traction surfaces. This is because the motor is mounted in reverse and spins clockwise instead of counter-clockwise. This makes the front of the car pitch forward during acceleration instead of rearward and helps keep the car flatter on power in the turns, which adds steering. But you end up giving up some forward bite and most of the cars I have seen run extra weight in the rear to compensate.

So the B5M people are trying to get corner speed by sacrificing rear grip with the 3-gear and we are trying to do the exact opposite with this kit for the KF2. Assuming this kit works well I think we are in a much better position for the future as tracks in the U.S. seem to be moving towards higher grip as a general trend. If the grip comes up just move the motor forward to keep the car flatter. This is a much more elegant design solution than turning the motor around and completely changing the vehicle dynamics IMO. And never mind you have to remember to use brake to pitch the car up in the air instead of throttle. That might be fine for Ryan Maefield but for people like me it is a nuisance.

I can't wait to try this kit out.....


It's always a pleasure to read you, here in south of France tracks are outside hard packed dusty tracks, the sv2 works but my kr works even more great.

After watching robin hood raceway euro warm up videos, I can see most curves are quite open and fast.

In our local tracks, there are more hairpins, I guess it could be the reason why rear motor are faster and easier to drive.

One of my mate,far much better than me, did the same experience with B5 and B5M.

Anyway, I look forward for a potential sv3, or I shall give a try to the KF with mid motor and super shorty+speedo in the same alignment (as you have tried).
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Old 08-01-2015, 10:12 AM   #372
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Thanks Mustrum. I really appreciate your perspective and those of the other people from other parts of the world. Is the race you are referring to at RHR the one they are preparing to use the new MM kit on Michael Orlowski's car? The Facebook photo of his car you shared seemed to suggest that.

I have been eager to see them update the SV2 as well and I wonder if there will even be an SV3 if this kit ends up working really well. It seems like for anyone needing even more rear grip the KR probably fits the bill. It is a business though and mid-motor cars are definitely the fashion here in the U.S. so even if the KR is better it might be a tough sell.

If they decide to go forward with just the KF2 platform then they at least need to sell a complete kit that comes with just the mid-motor configuration. Otherwise, to get the car in a configuration most relevant for us here in the States it will cost north of $600. Today you would need to buy the main KF2 kit, this new MM kit, the reversible shock tower trans housing kit and a ball diff plus the new body that accommodates the motor position of the MM kit. Nobody is going to spend that when they could get TWO B5M factory lites for less money. I think a nice package would be the KF2 with nothing but the MM parts, the new body shell, reversible shock kit and a ball diff instead of a gear diff for about $449 USD. The low grip and forward motor position parts would all be option parts. That would put them at the higher end up there with the Kyosho kits but this car would need absolutely nothing to be competitive right out of the box.

The only reason I am willing to spend the money on this new kit is because I have so much time and money invested in it I am ready to try just about anything to get it right. I am thankful that Schumacher has decided to take their customers' feedback and at least try to give us something that should hopefully meet our needs.
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Old 08-01-2015, 11:13 AM   #373
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Yes it's the video where Michal used the proto, after chatting with him he sent me his set-up, when I asked him why not using the kr he answered kf was 1s faster per lap.
Well much for him but not for a local racer like me as I'm more involved i tuning parts and setups.

Despite being cougar addict, not the old ladies, including , parts and upgrades and 3 super shorty lrp and an lrp speedo (well I can't run a mixed of orion and lrp...) I'm not far from 1000€ ouch! Much bucks for not being sure of the result. So I look forward for sv3 or XB2 or HB D216, as these manufacturers reach schuey quality.
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Old 08-01-2015, 11:42 AM   #374
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Yes it's the video where Michal used the proto, after chatting with him he sent me his set-up,
Could you post a link to the video?

Could you post his setup with the KF2mm?
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Old 08-01-2015, 11:50 AM   #375
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That's really interesting. A whole second per lap is a lot at that level. Now I'm even more eager to try out this MM kit seeing as how it was outperforming the KR on a surface typically judged as more suitable for the KR. The video I watched showed most cars running small pin tires in the rear and ribbed tires in the front. Is that correct?

If you would be willing to share his KF setup with us here or email it to me personally that would be really helpful. But I understand if you aren't comfortable with that or would want to ask his permission first.

I think the race starts Monday if I remember correctly? I'd love to see Michal (or anyone else for that matter!) beat Lee Martin....
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