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Ask Ray Munday - JConcepts, Reedy, Associated Aussie Support Thread

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Ask Ray Munday - JConcepts, Reedy, Associated Aussie Support Thread

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Old 03-27-2014, 02:11 PM
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Originally Posted by mookins View Post
Hi Ray,

First, let me say thank you for this great thread. Spend hours going through it from the start (only at page 20 thus far) and find it amazingly helpful. Also thank you for all the great work you do for the RC community and especially with KEORCA where I am recently a member.

I have a huge list of questions for you but I will start with my more immediate ones.

With regards to the B44.1 and its ball diff, do you know what material the gears are made from and if there is a recommended lubricant for them and whether it is recommended to lubricate them at all? I am thinking a silicon grease would be good for these if lubricating them were to be recommended.

With regard to the adjustment of the diff, I understand it is a very subjective feel type of setting, but I am not sure where my ball park should even be.
The Associated manual instructs the reader to tighten it up "all the way" then back it off some. How far/tight is "all the way"? Until the spring compresses to its theoretical minimum collapsed height or until it is fully compressed? Either way both are a little difficult to judge. I don't want to cause Brinelling of the bearing races (the washers).
I had an idea on getting it dialled in more repeatably. One idea was to use a cordless drill with a clutch and use it to drive one of the outdrives while holding the other still. Then you could adjust the diff until you get to a specific clutch setting to slip. This could be fairly repeatable.
Any thoughts on this proposed method? Too much fiddling for little benefit perhaps?

-Mikey
Hi Mikey, glad you like the thread. Wish I had time to do more!

B44 diff - I use the clear ball diff grease to lubricate the gears. Ive tried moly grease in the past but it seems messy and not as effective as the ball diff grease.

Ive looked at making something to measure the diff, but the torques required are very low. Basically you will feel when the diff is fully tightened when you tighten the adjuster screw. You can feel the adjuster nut bottom out. If you back it off around 1/16 to 1/8 from there you will be in the ballpark. It takes a little practice to feel the diff tightness but its not too difficult. Best to see myself or one of the more experienced guys at the track and they can help you out.

A key point with the diff is that you need to run it in. It will loosen a little after run in. I usually put the car with one side touching the ground and the other in the air, then run it at about 30% throttle for about 3 minutes. Repeat for the other side. Then re-adjust the diff. For the first run with a new diff, if you hear it slip at all, you need to stop immediately as this will damage the diff.

Originally Posted by Jouster View Post
I got the Savox SC-1251MG servo. Alot of guys seemed to be using this and the specs seemed to fit your previous suggestions. I've already fitted the servo and found an immediate improvement.
Ok great! Just be aware that as it is a very light servo, if the track gets very grippy or bumpy you may find the front wheels leave the ground more. If so, add some ballast in behind the servo. I ran quite a heavy servo (70g) and this helped a lot, especially in mod. If the track is low traction and you are running in stock, this light weight will probably help out.
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Old 03-31-2014, 09:34 AM
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Hi Ray,

I have some questions on the ballistic brushless motors.
First, do you know if there are different rotors between mod and spec motors for performance? I know there are tuning rotors, but just wondering if they both came with the same size or build.

Next, what is a good timing starting point on the motor for mod? Specifically a 6.5, for a large outdoor track.

Lastly, what do you usually run in terms of esc timing and boost?

I ask because I had a 25.5 stator blow out on one of my onroad cars, and I'd like to change it over with a 6.5 stator for my mod 4wd buggy.

Thanks, Ted
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Old 03-31-2014, 07:37 PM
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Originally Posted by mschumi101 View Post
Hi Ray,

I have some questions on the ballistic brushless motors.
First, do you know if there are different rotors between mod and spec motors for performance? I know there are tuning rotors, but just wondering if they both came with the same size or build.

Next, what is a good timing starting point on the motor for mod? Specifically a 6.5, for a large outdoor track.

Lastly, what do you usually run in terms of esc timing and boost?

I ask because I had a 25.5 stator blow out on one of my onroad cars, and I'd like to change it over with a 6.5 stator for my mod 4wd buggy.

Thanks, Ted
Hey Ted,

As far as I am aware, all of the Ballistic motors come with the same 12.5mm rotor so you should be able to run the 6.5 stator.

I run a 6.5T in my 4wd with the following settings:
- 9.3:1 FDR (21/78 on B44)
- 35deg static timing
- if the track has good grip and a longer straight, I run 15 deg boost from 19-29K RPM. If its very slippery, I generally dont touch the boost.

Hope this helps

Ray
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Old 03-31-2014, 08:50 PM
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Originally Posted by ray_munday View Post
Hey Ted,

As far as I am aware, all of the Ballistic motors come with the same 12.5mm rotor so you should be able to run the 6.5 stator.

I run a 6.5T in my 4wd with the following settings:
- 9.3:1 FDR (21/78 on B44)
- 35deg static timing
- if the track has good grip and a longer straight, I run 15 deg boost from 19-29K RPM. If its very slippery, I generally dont touch the boost.

Hope this helps

Ray
For sure! Thank you. I'm around that gearing with my 7.5 running boost. I'll have to try it out with the new motor. Thanks for the info.
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Old 03-31-2014, 09:41 PM
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Hey Ray -- Seems like everywhere I look, I get a different answer on ackerman. I'm running the JC rack on my B44, and I was under the impression that running the location towards the front of the car would provide more steering, from a geometry perspective.
However, I thought running the ackerman location towards the rear of the vehicle would cause the steering to be more responsive (but have less steering geometry wise).

Please let us know. Thx!
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Old 04-01-2014, 02:13 AM
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Originally Posted by skrichter View Post
Hey Ray -- Seems like everywhere I look, I get a different answer on ackerman. I'm running the JC rack on my B44, and I was under the impression that running the location towards the front of the car would provide more steering, from a geometry perspective.
However, I thought running the ackerman location towards the rear of the vehicle would cause the steering to be more responsive (but have less steering geometry wise).

Please let us know. Thx!
Hi mate,

tricky question. The answer is not always consistent because if you go too far one way or the other you can get opposing results.

Basically, as you move the rack position further forwards, you increase the ackerman. This means that the inside wheel will turn further than the outside. In my experience, this tends to make the car turn harder into the tighter corners (the inside wheel acts like more of a brake and helps to pivot the car, plus you can get some additional caster jacking effects which plant the inside front into the ground harder). In higher speed corners, it tends to smooth out the steering up to a point.

I generally run the ackerman in the middle hole on the JC rack (equivalent to the front hole on the AE rack). With the B44.2 longer wheelbase chassis, we all moved forward on the rack to give a bit more low speed rotation since the longer chassis was more docile.

If a track has lots of low speed sections, try more ackermann. If it is more flowing, try less.

Hope this helps.

Ray
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Old 04-02-2014, 03:47 AM
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Hey Ray,

Thanks for a your help so far. I have a driving question. Trying to reduce my times at Keilor in practice and they are hovering around 33-34 secs consistently with a 32sec my best lap time within that same run.

For the sections of the track after the main sweeper after the straight do you try and drive in straight lines and break hard late then turn the next corner? Is there a faster way around the track? I feel I can gain some time on that section of the track up until the drop off and feel that's the best way to drive. Is there a faster way?

Thanks
Jason
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Old 04-02-2014, 03:52 AM
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Default b44.1 diff gear meshing

Hi Ray,

After a full rebuild of the front and back diffs of my car and getting the slip set, my car ran really well, thanks to your prior advice.

However, I was running a new set of gears in the front, under the impression the nylon dust I had found in the front diff case was a sign of clapped out gears.
After running the new gears for an hour or so I noticed it was cogging a bit. I opened up the case and realised the tips of the gears were snapping off and getting stuck in the roots of the gears. I have done a fair bit of work with gears in an industrial application and gears are almost always truncated so I was a little surprised to find that these were not. I figured this was a shoddy manufacturing batch or something, cleared the broken tips away and ran the diff for the remainder of the afternoon (another 3 hours or so).
Ran again a few nights later and the diff gears got noisier and then failed, about 50% of the teeth are gone.
The rear gears are perfect. The original front ones look just like the rear, in good condition but as mentioned were replaced due to the dust.

My questions are
a) is this to be expected with plastic gears in RC cars?
b) is there are breaking in procedure one should follow to let the gears wear themselves in since they are not precision machined/ground gears?
c) do you have any tips on setting gear mesh with the B44.x ball diffs?

-Mikey
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Old 04-03-2014, 05:20 AM
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Originally Posted by jasonx View Post
Hey Ray,

Thanks for a your help so far. I have a driving question. Trying to reduce my times at Keilor in practice and they are hovering around 33-34 secs consistently with a 32sec my best lap time within that same run.

For the sections of the track after the main sweeper after the straight do you try and drive in straight lines and break hard late then turn the next corner? Is there a faster way around the track? I feel I can gain some time on that section of the track up until the drop off and feel that's the best way to drive. Is there a faster way?

Thanks
Jason
Hi Jason,

Through the back-back hairpin section, there are 2 main ways to attack it.
1) Point and shoot - drive a straight line from one apex to the next. You can accelerate and brake hard in a straight line. Once the car starts to turn, tap the brake again to make it rotate and that way it is lined up for the next straight earlier. With a rear motor vehicle this tends to be the fastest way to drive. It takes a bit of practice to get the brake technique right but when you do the car will rotate and then punch out of the corner in a single motion.
To make this technique fast you need to be as close to the curb as possible, and not 'over-rotate' or you will lose time. You can practice this technique anywhere with some bald tyres and a couple of obstacles (potplants etc) to rotate around using the brakes.

2) Flowing. This technique turns the hairpins into 'esses' where you take a more flowing line and can therefore corner at higher speed, however you will cover a longer distance. This works well for mid motor vehicles and those with a bit less power.

Im currently in the middle of a crazy work schedule, but once that's over I plan to run a coaching day at Keilor where we can run through some of the line choices and techniques available.

Originally Posted by mookins View Post
Hi Ray,

After a full rebuild of the front and back diffs of my car and getting the slip set, my car ran really well, thanks to your prior advice.

However, I was running a new set of gears in the front, under the impression the nylon dust I had found in the front diff case was a sign of clapped out gears.
After running the new gears for an hour or so I noticed it was cogging a bit. I opened up the case and realised the tips of the gears were snapping off and getting stuck in the roots of the gears. I have done a fair bit of work with gears in an industrial application and gears are almost always truncated so I was a little surprised to find that these were not. I figured this was a shoddy manufacturing batch or something, cleared the broken tips away and ran the diff for the remainder of the afternoon (another 3 hours or so).
Ran again a few nights later and the diff gears got noisier and then failed, about 50% of the teeth are gone.
The rear gears are perfect. The original front ones look just like the rear, in good condition but as mentioned were replaced due to the dust.

My questions are
a) is this to be expected with plastic gears in RC cars?
b) is there are breaking in procedure one should follow to let the gears wear themselves in since they are not precision machined/ground gears?
c) do you have any tips on setting gear mesh with the B44.x ball diffs?

-Mikey
Basically with the plastic gears they need to be meshed correctly and have some lubrication. Even then, they are a consumable part which will wear and will need replacement from time to time.

I build them with ~5 of the shims on the ring gear side of the diff. The mesh is a little tight when you put it together. Use the clear diff lube to lubricate the gears. Once you have re-assembled the transmission case, its good to run the diffs in for a few minutes at about 30% power. Sometimes it takes a run on the track to fully bed them in.

If you run the gears too loose, the teeth chip off very easily. Too tight, and they overheat and wear quickly. In mod, its better to be a little tight rather than too loose. If the tips are snapping off, its probably a sign of a mesh that's too loose.

While you rebuild the transmission, make sure that the housing is OK. I had a cracked transmission housing a few years back and it was spreading under load. I couldn't work out why I was going through gears at a stupid rate of knots until then.

Im hoping that future versions will be released with metal gears as in all honesty, the modern power output of vehicles coupled with the grip from modern tyres / tracks is greater than what the plastic gears were designed for.

Ray
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Old 04-03-2014, 05:35 AM
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Hi Ray,

I race in the UK and i am after a little advice. We run mostly on astro turf and i am struggling to get the shocks right. I run mostly 2 x 1.7 hole 35wt oil with Yellow springs up front and 2 x 1.7 hole 30 wt green springs on the rear. The car just doesnt seem to want to change direction well and it doesnt fly right in the air. Is there something i can do help this situation? Any hlep and advice you can give is great.

The car has durango gear diffs with 10k in front and 7 k in rea, if that helps

Cheers

Lee
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Old 04-03-2014, 05:43 AM
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Originally Posted by 99windy View Post
Hi Ray,

I race in the UK and i am after a little advice. We run mostly on astro turf and i am struggling to get the shocks right. I run mostly 2 x 1.7 hole 35wt oil with Yellow springs up front and 2 x 1.7 hole 30 wt green springs on the rear. The car just doesnt seem to want to change direction well and it doesnt fly right in the air. Is there something i can do help this situation? Any hlep and advice you can give is great.

The car has durango gear diffs with 10k in front and 7 k in rea, if that helps

Cheers

Lee
Hi Lee,

The biggest thing I can see is using 1.7mm pistons on the front. Generally we only use 1.6mm pistons, and sometimes 1.5mm if the grip is very high. Unless that's a typo, I'd suggest using 35/2hx1.6mmm front pistons as a starting point.

The front will slap very hard on take off and landing with the 1.7s installed, especially if you run a lower ride height on astro. Do you run on high grip astro or is it low traction?

I run the same spring combination you do, with 1 down travel limiter within each shock. I run ride heights of 22/21 f/r on a bumpy track and 21/20 on a smoother track.

Hope this helps.

Ray
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Old 04-03-2014, 07:31 AM
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Ray:

I see on your setup that you like to run 18% drag brake. What is the % value relative to? I dialed in 15% (my ESC is variable by 5% increments) and it kinda slowed down, then bumped it up to 25% and it was maybe a little more aggressive. But, it sure wasn't 25% of my total braking power. HobbyKing Trackstar Turbo 120A ESC and 9.5 Trackstar brushless in a 4.2.

And, one more question while I wait for parts bag ASC9864 to arrive. The car came with C hubs, they are 2mm lower that the A hubs, you recommend a 2mm washer on the rear inner mount, if the hub tower is 2mm lower and I run with no washer (2mm lower) the two links would be parallel, right. So, that would lower the roll center 2mm below CG. If I bumped the inner washer up 1.5mm it would be very nearly the same moment as the A with a 2mm washer. What would be different? I assume the camber rise would be different, but would like to just get my head around roll centre changes.

Thanks
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Old 04-04-2014, 04:37 PM
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Originally Posted by clw View Post
Ray:

I see on your setup that you like to run 18% drag brake. What is the % value relative to? I dialed in 15% (my ESC is variable by 5% increments) and it kinda slowed down, then bumped it up to 25% and it was maybe a little more aggressive. But, it sure wasn't 25% of my total braking power. HobbyKing Trackstar Turbo 120A ESC and 9.5 Trackstar brushless in a 4.2.

And, one more question while I wait for parts bag ASC9864 to arrive. The car came with C hubs, they are 2mm lower that the A hubs, you recommend a 2mm washer on the rear inner mount, if the hub tower is 2mm lower and I run with no washer (2mm lower) the two links would be parallel, right. So, that would lower the roll center 2mm below CG. If I bumped the inner washer up 1.5mm it would be very nearly the same moment as the A with a 2mm washer. What would be different? I assume the camber rise would be different, but would like to just get my head around roll centre changes.

Thanks
Hi,

with the c hubs you should run them with no washers under the inner ballstud (some actually shave the ballstud further). The c hub with a lower inner gives a different feel to the rear of the car - it allows a more progressive rotation and is usually used on indoor clay tracks. . But the A hub and 2mm under the ballstud generally feels more locked in on corner exit on outdoors tracks.The difference is not massive, so it will be fine to run to start with.

Moving the link up and down in parallel does change the roll centre a little, and it also changes the way that the roll centre moves as the car rolls. It also impacts the camber change of the tyres.

Roll centres are a difficult concept to explain and understand... one day when I get the time I will try and go through it more. I write for a magazine here and its a topic I have been avoiding LOL.

Drag brake: It will be different for each ESC. Basically I use more on my 2wd than my 4wd. Its a great tool to help the car have better turn in without having to use the brakes so much - its hard to be precise and consistent with the brakes for small movements without sometimes spinning out. Its equivalent to 18% brake trigger movement, but not necessarily 18%of the total brake force depending on how linear your brake setting is.
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Old 04-04-2014, 04:52 PM
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Default B5 Setups

Last weekend I raced at the Knox Cup in Melbourne, round 1 of the Vic drivers series. Was a big day with 130 entries and the track was old school non-sugar dirt which grooved up through the day but had plenty of bumps.

We had a successful debut for the B5 with me, Andrew Selvaggi and Glen Bonetti 1-2-3 in 2w mod!

The car is fantastic out of the box, but we are still learning and trying things to get the most out of it on each surface. We ran the rear motor car here. As the day progressed the track got a little bumpier with higher traction and to calm it down, the main change I made was to add weight under the batteries. I used a full saddle pack plus a 60g lead plate under the batteries (total weight of the car 1640g) and it was more settled. On a smooth track I don't know if its necessary.

Compared to the B4, the car feels more responsive and jumps better. Its also very smooth in the high speed corners where the B4 tended to get a bit edgy.

Ive posted my setup here:


http://www.keilorrc.org.au/setups/20...y_Knox_Cup.pdf
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Old 04-04-2014, 06:59 PM
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Originally Posted by ray_munday View Post
Hi,

Its equivalent to 18% brake trigger movement, but not necessarily 18%of the total brake force depending on how linear your brake setting is.
Makes sense, I think I have some negative EXPO dialed in.

I learn more on your thread than anywhere else, great job!
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