F104 Pro II - Necessary Upgrades

[87lc2 2575]

Thank you @Jonathon Gillham   I will certainly try the Tamiyas since I have them, but the Exoteks are much softer and have a feeling they'll work better on our surface.  Its asphalt, but gets a lot of prep and has good grip. 

I'll look around for the tires you mentioned that fit Tamiya wheels and also pick up some Exotek wheels so I can at least run these tire I bought.  Just waiting on my shipment from PlazaJapan and I can get the kit built.  May get the body painted this weekend so I dont have to worry about that later.

[Jonathon Gillham 4513]

2 hours ago, 87lc2 said:

Thank you @Jonathon Gillham   I will certainly try the Tamiyas since I have them, but the Exoteks are much softer and have a feeling they'll work better on our surface.  Its asphalt, but gets a lot of prep and has good grip. 

I'll look around for the tires you mentioned that fit Tamiya wheels and also pick up some Exotek wheels so I can at least run these tire I bought.  Just waiting on my shipment from PlazaJapan and I can get the kit built.  May get the body painted this weekend so I dont have to worry about that later.

If you find the Pit Shizumu soft rears and med fronts for asphalt then let me know where. I got some years ago and they have now died but I can't find replacements. Tyres are most of the tuning in F1 and my TRF102 was able to make the podium with those tyres (of up to 10 cars at club level, but you know, a podiums a podium!)

[87lc2 2575]

6 hours ago, Jonathon Gillham said:

If you find the Pit Shizumu soft rears and med fronts for asphalt then let me know where. I got some years ago and they have now died but I can't find replacements. Tyres are most of the tuning in F1 and my TRF102 was able to make the podium with those tyres (of up to 10 cars at club level, but you know, a podiums a podium!)

Yes it is, doesn't matter how many cars.   I'll let you know if I happen to find them, no luck yet...For now going to order some Exotek dish wheels so I can get it on the track then go from there.  Feeling the Exotek tires I'm sure they'll work well as the compound feels similar to USGT tires and they work perfectly at our track.

[87lc2 2575]

Finally started on the F104 tonight and already hit a snag - When tightening the M4 Diff Joint nut the threads snapped off.   Was using a box wrench and noticed that even when tight the spur gear was able to move a bit side to side so I may have overdone it.  I'm not too familiar with ball diffs (its been a while) - should the spur be nice and tight or does it move around a bit?  I double checked the manual and I had everything else right, seemed odd to me.

Luckily the Aluminum Diff Housing comes with the shaft and they are available stateside so I can have one in a few days.  I can get just the shaft but only from RCMart and don't feel like waiting that long. 

 

[87lc2 2575]

One more thing - Someone earlier in the thread mentioned when using a low profile servo that you do not have to cut the mounting tabs off.  I don't see how this could be possible looking ahead in the manual - Low profile or not those tabs need to come off.  Just wanted to confirm in case I'm missing something.  Would really prefer not to cut them but if I have to not a huge deal. 

[Pylon80 1390]

1 minute ago, 87lc2 said:

Low profile or not those tabs need to come off. 

They do not need to come off with a low profile servo. They are not interfering with anything if you leave them on and that leaves your servo reusable for a different car.

[87lc2 2575]

Just now, Pylon80 said:

They do not need to come off with a low profile servo. They are not interfering with anything if you leave them on and that leaves your servo reusable for a different car.

Thank you, I'm glad that's the case.  How is this possible though - It looks like the servo sits on the chassis plate?   Haven't actually done it yet, but looking at the manual it looks like it sits flat on its side.

[TurnipJF 8779]

1 hour ago, 87lc2 said:

Thank you, I'm glad that's the case.  How is this possible though - It looks like the servo sits on the chassis plate?   Haven't actually done it yet, but looking at the manual it looks like it sits flat on its side.

 You mount it flat on its base like this:

In some rare cases you may need to fiddle with the length of the standoffs between servo saver and ball nuts, but in most cases everything clears without issue. 

[Jonathon Gillham 4513]

4 hours ago, 87lc2 said:

Finally started on the F104 tonight and already hit a snag - When tightening the M4 Diff Joint nut the threads snapped off.   Was using a box wrench and noticed that even when tight the spur gear was able to move a bit side to side so I may have overdone it.  I'm not too familiar with ball diffs (its been a while) - should the spur be nice and tight or does it move around a bit?  I double checked the manual and I had everything else right, seemed odd to me.

Luckily the Aluminum Diff Housing comes with the shaft and they are available stateside so I can have one in a few days.  I can get just the shaft but only from RCMart and don't feel like waiting that long. 

 

I feel your pain here as I really struggled with the floating spur. It does move around a bit and its fine.

[87lc2 2575]

@TurnipJF - Thank you!  That's perfect.

@Jonathon Gillham - Yea, I was definitely not expecting that.  So the spur actually does float like that?  I guess when in use it will stay in one spot, but I was expecting it to be nice and firm.  Lesson learned I guess...Part is on the way and I should be able to get back to it in a few days. 

[Pylon80 1390]

8 hours ago, TurnipJF said:

 You mount it flat on its base like this:

In some rare cases you may need to fiddle with the length of the standoffs between servo saver and ball nuts, but in most cases everything clears without issue. 

@87lc2 note that the forward and aft location where you attach the servo - with double sided tape - is important as this is how you tune Ackerman. The manual won't mention it. As a starting point you can aim to have the servo saver about 2mm more forward then the uprights, if that makes sense. That's quite visible on Turnip's picture.

 

[87lc2 2575]

1 hour ago, Pylon80 said:

@87lc2 note that the forward and aft location where you attach the servo - with double sided tape - is important as this is how you tune Ackerman. The manual won't mention it. As a starting point you can aim to have the servo saver about 2mm more forward then the uprights, if that makes sense. That's quite visible on Turnip's picture.

 

Thank you, I will use that as a starting point.  I can definitely see it in his photo.  A bit new to the on road stuff, what exactly does moving the saver fore/aft do as for as steering is concerned?  I guess what I'm asking is how does changing the ackerman affect the car in practice?

[Pylon80 1390]

1 hour ago, 87lc2 said:

Thank you, I will use that as a starting point.  I can definitely see it in his photo.  A bit new to the on road stuff, what exactly does moving the saver fore/aft do as for as steering is concerned?  I guess what I'm asking is how does changing the ackerman affect the car in practice?

In very rough terms, more Ackerman will make your steering more responsive with perhaps the car becoming a little harder to drive especially on a higher grip track. It will however be more optimized for a very twisty track where the low speed infield matters.

The opposite is true, with less Ackerman making the steering more mellow and optimized for a faster track with a long straight and larger sweepers.

Finally, you would never go with "reverse Ackerman" whereby the servo would be behind the uprights. At least I have never seen it and it wouldn't make much physical sense.

[87lc2 2575]

Excellent, thank you @Pylon80  So in my case I'll go with the 2mm for now.  Don't want the car to be too responsive at this point.  At least not until learn to drive it.  It will mostly be run on a large outdoor track anyway. 

[TurnipJF 8779]

1 hour ago, Pylon80 said:

Finally, you would never go with "reverse Ackerman" whereby the servo would be behind the uprights. At least I have never seen it and it wouldn't make much physical sense.

I have never seen reverse Ackerman purposefully built into a RC car, although some (generally crawler types) end up having it anyway due to design compromises elsewhere.

In full-size F1 though, reverse Ackerman is used regularly. Instead of trying to get the inner and outer tyre to each follow their natural arc of travel around a corner as with conventional Ackerman, reverse Ackerman is used to place a greater turning load on the outer tyre as it has more weight transferred onto it in a turn, giving it more grip. It looks weird, but it works, at least it does at 1:1 scale, where all 4 wheels have brakes, and the bias can be adjusted front to rear.

In a 1/10 scale F1 though, the car is already prone to being tail happy due to the rear wheels doing all the braking, so we generally want less grip up front, not more. You'll find that most people run harder, less grippy tyres on the front and softer, grippier ones on the rear for example. 

[87lc2 2575]

Yes, that's what I hear @TurnipJF - In fact, most of the local racers have recommended Exotek tires (soft rear, medium front) for our track and that's what I plan on running.  I do expect the F1 to be a bit tail happy and a small handful to drive fast, but looking forward to the challenge.

[Pylon80 1390]

43 minutes ago, TurnipJF said:

I have never seen reverse Ackerman purposefully built into a RC car, although some (generally crawler types) end up having it anyway due to design compromises elsewhere.

In full-size F1 though, reverse Ackerman is used regularly. Instead of trying to get the inner and outer tyre to each follow their natural arc of travel around a corner as with conventional Ackerman, reverse Ackerman is used to place a greater turning load on the outer tyre as it has more weight transferred onto it in a turn, giving it more grip. It looks weird, but it works, at least it does at 1:1 scale, where all 4 wheels have brakes, and the bias can be adjusted front to rear.

In a 1/10 scale F1 though, the car is already prone to being tail happy due to the rear wheels doing all the braking, so we generally want less grip up front, not more. You'll find that most people run harder, less grippy tyres on the front and softer, grippier ones on the rear for example. 

Very interesting facts about 1:1 scale, I had no idea! 👍

[TurnipJF 8779]

42 minutes ago, Pylon80 said:

Very interesting facts about 1:1 scale, I had no idea! 👍

I only found out about a month ago myself! 😀

[87lc2 2575]

OK guys, got the new diff shaft and the car is together.  Mounting electronics in these is fun   

Anyway, having an issue that is not car related, its motor related.  Using a 25.5 Hobbywing V10 G3R  - https://www.amainhobbies.com/hobbywing-xerun-v10-g3r-competition-stock-spec-brushless-motor-25.5t-hwa30401133/p1148600?gclid=Cj0KCQjwx5qoBhDyARIsAPbMagDy56ld0KhV5EYmwypnefpuxq4jivbnbT-UBbsWe8Iu90cdAyqTwC0aAlkbEALw_wcB

When taking it out of the box I noticed the motor was very tight, but didn't think too much of it.  Once I had it installed and went to give the car throttle it made some horrible clicking noises and then would go fine.  Figuring I must have screwed something up with the diff I pulled the motor out and ran it with no load.  Sure enough under light throttle the motor just clicks and will move after 1/4 throttle or so.  I've never had this issue with any motor, sensored or non-sensored so wondering what's going on here.  Double checked all connections and everything is correct, no issues there.  Possible I got a bad motor?  As I said it is very tight to turn by hand, much tighter than any other motor I've ever installed. 

One note - It comes set at 42 degrees timing, backed it down to the minimum (30) and it was a bit better, but not perfect.   Since there are no parts making contact in a brushless motor (other than bearings), what could be causing this thing to hang up?  

I'll post in the electrics section as well, but figured I'd ask here as you guys have helped a lot to this point. 

[Jonathon Gillham 4513]

It sounds like a faulty motor to me. I've had ones that are super noisy when off throttle but that was just much stronger magnets than the previous motor which sounded notchey when decelerating.  I'd be sending it back and getting a new one. 

[87lc2 2575]

Yea, I guess we'll see how good the HW warranty is, I've heard they can be a pain unfortunately.  I did a bit more testing just to be sure this morning - swapped sensor wires, tired the motor on another ESC, and even tried another motor with the ESC in the car and everything worked perfectly except for this motor.   It's actually worse with the sensor wire installed so I guess its a bad sensor board?  I have never had a brushless motor apart but took this one apart and there's nothing out of place in there.  Not much to these things actually, figure it has to be bad internal electronics.

[Pylon80 1390]

1 hour ago, 87lc2 said:

Yea, I guess we'll see how good the HW warranty is, I've heard they can be a pain unfortunately.  I did a bit more testing just to be sure this morning - swapped sensor wires, tired the motor on another ESC, and even tried another motor with the ESC in the car and everything worked perfectly except for this motor.   It's actually worse with the sensor wire installed so I guess its a bad sensor board?  I have never had a brushless motor apart but took this one apart and there's nothing out of place in there.  Not much to these things actually, figure it has to be bad internal electronics.

If you are in the US and got it from AMain, in my experience they are really easy and customer friendly. They will take that motor back immediately and apologize

Before you do that though, in case you haven't tried already:  with the motor outside of the car and a pinion attached, flick the pinion between your fingers. There should be the usual resistance due to the magnets but otherwise it should be smooth and spin a few turns before stopping. Then, still outside of the car, I would try spinning the motor under its own power. It should hum nicely and silently (you would only hear the cutting frequency from the ESC which you are probably already familiar with. That is to make sure nothing mechanical on the car side is causing the issue. If both these tests result in a bad sound then I would think you have a bad motor

[87lc2 2575]

2 minutes ago, Pylon80 said:

If you are in the US and got it from AMain, in my experience they are really easy and customer friendly. They will take that motor back immediately and apologize

Before you do that though, in case you haven't tried already:  with the motor outside of the car and a pinion attached, flick the pinion between your fingers. There should be the usual resistance due to the magnets but otherwise it should be smooth and spin a few turns before stopping. Then, still outside of the car, I would try spinning the motor under its own power. It should hum nicely and silently (you would only hear the cutting frequency from the ESC which you are probably already familiar with. That is to make sure nothing mechanical on the car side is causing the issue. If both these tests result in a bad sound then I would think you have a bad motor

HW got back and wants me to send it to them for analysis - I think I'll try Amain first.  I'm sure they'll take it back with no issue.

I have done what you said already and the motor is extremely tight.  Spinning the shaft by hand (with or without pinion) It will maybe spins one or two clicks but that's it.  When I first got the motor I thought, "Wow, that's tight!" thinking it was a good thing that the magnets were so strong.  I'm not too familiar with competition brushless motors yet so thought it was normal. 

I have also been running it outside of the car and at 1/4 throttle or less the shaft just hesitates and will not spin - also makes a cogging sort of noise.  Once I give it a bit more throttle it will turn.  Interestingly enough it will respond to light throttle sooner without the sensor wire plugged in and with less timing, but still cogs badly at very slight throttle when out of the car. 

 

 

[Pylon80 1390]

1 hour ago, 87lc2 said:

HW got back and wants me to send it to them for analysis - I think I'll try Amain first.  I'm sure they'll take it back with no issue.

I have done what you said already and the motor is extremely tight.  Spinning the shaft by hand (with or without pinion) It will maybe spins one or two clicks but that's it.  When I first got the motor I thought, "Wow, that's tight!" thinking it was a good thing that the magnets were so strong.  I'm not too familiar with competition brushless motors yet so thought it was normal. 

I have also been running it outside of the car and at 1/4 throttle or less the shaft just hesitates and will not spin - also makes a cogging sort of noise.  Once I give it a bit more throttle it will turn.  Interestingly enough it will respond to light throttle sooner without the sensor wire plugged in and with less timing, but still cogs badly at very slight throttle when out of the car. 

 

 

Hmm spinning by hand without a pinion is not supposed to be possible unless you have very strong fingers indeed With a pinion you can definitely do it and it will spin - silently - for a couple of turns. Under power the cogging without the sensor cable is normal (don't run sensor-less if you don't have to, it's so terrible).

[87lc2 2575]

10 minutes ago, Pylon80 said:

Hmm spinning by hand without a pinion is not supposed to be possible unless you have very strong fingers indeed With a pinion you can definitely do it and it will spin - silently - for a couple of turns. Under power the cogging without the sensor cable is normal (don't run sensor-less if you don't have to, it's so terrible).

It's actually better without the sensor cable plugged in...weird.  I put the motor on my other HW brushless ESC and same thing.  Tried a Reedy motor on this ESC and it was perfect.  For now I just ordered another Reedy motor since I'm trying to get it going for this weekend, but hopefully I can get a replacement motor from HW at some point.

Also - Does anyone run these on CRC Black Carpet?  If so what tires would you recommend?  I plan on running asphalt most of the time, but there's a local race on carpet this weekend and may bring the car out, just not sure if my Exotek tires will be good on carpet.  They feel like they'll have way too much grip.