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For the mechanics


maddmaxx

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15 minutes ago, bikeman564™ said:

awesome pics

Not my Phone.  That's my Nikon L800 and I finally gave up on ambient lighting and tried auto flash with macro to get the sharper closeups.  The L800 is an older version of those large optics motorized zoom non changeable lens "big boy point and shoot" cameras.  Other than setting macro mode the camera did all the work.

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Where groupW's mention of changing roll center can be seen best in the first picture of the left rear suspension.  Looking at the upper control arm ball joints you can see that the location can be changed, in, out or a combination of both (changing the length of the arm.  In addition the height of the inner ball joint can be changed by altering the thickness of the spacer under the ball where it screws in.  All of these changes alter the shape of the parallelogram that is the rear suspension.  Those changes have a couple of different effects, from moving the roll center (the mathematical point around which the chassis rolls during cornering) to altering the "camber change" (the tip in or out of the top of the tire as the suspension moves up or down.  When I raced this chassis as a B5 off road buggy, roll center was an important tuning tool.  On the drag car, so far I'm more interested in the camber change as I want to maintain the flattest contact patch of the drag slicks as the rear suspension "squats".

There's a different "secret" thing happening up front as I have aluminium travel "limiters" on the shock shafts.  There the front end rises during launch to transfer weight to the rear wheels and then rapidly settles back down on the limiters so that the suspension effectively moves into a solid, no more movement situation.  Because of this if the car starts to steer to the left or right at speed there is no ability for it to "tuck" and steer harder in that direction.  All roll of the front end is removed at that point.

One of the magic tools I may purchase next year is an actual set of scales, one for each wheel to accurately measure the weight on wheels for each.  I can then set the preload on each corner in an attempt to get the car to run as straight as possible.

Next year there will also be closeup video of the launch to check on tire spin and suspension movement.

This is what happens when an engineer mind tackles RC drag racing.  There are others out the much faster than me who operate on "tribal knowledge".

Fun.

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37 minutes ago, donkpow said:

So who crawls under there to grease the joints?

I have a lift.  It's that pinkish purple thing under the chassis in the first pic.  :nodhead:

Truth however, very few of the joints are lubed.  Because the car is serviced so often it's better to run them dry then to have the lube attract dust and dirt.  There simply isn't the bearing surface load in something this size to need oil /grease to act as a load carrier.  The CV joints are greased but that's a high rpm friction point.  At 20,000 plus rpm the motor bearings are oiled.

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52 minutes ago, maddmaxx said:

I have a lift.  It's that pinkish purple thing under the chassis in the first pic.  :nodhead:

Truth however, very few of the joints are lubed.  Because the car is serviced so often it's better to run them dry then to have the lube attract dust and dirt.  There simply isn't the bearing surface load in something this size to need oil /grease to act as a load carrier.  The CV joints are greased but that's a high rpm friction point.  At 20,000 plus rpm the motor bearings are oiled.

We were told our gas engines were good to 30,000 rpm. When the rod popped, it got quiet quickly. We would just say "30,001"..

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13 minutes ago, groupw said:

We were told our gas engines were good to 30,000 rpm. When the rod popped, it got quiet quickly. We would just say "30,001"..

When I ran the gas cars in ROAR 73 and 74 we didn't turn that many rpm.  I did however race 1/2A planes for a while and the same thing would happen.  Scream scream scream thud followed by the sound of air rushing over the wings as you did another lap slowing enough to land.  I like the electrics better and I'm sure my neighbors do too. 

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7 hours ago, maddmaxx said:

Examples of how closely the RC car follows the technology of full sized cars..........or not.

The rear suspension from the left side showing upper and lower control arms, the axle shaft, the upright, the left end of the anti roll bar and the transmission case.  There is a cv joint inside the upright and a "slider joint" at the transmission end of the axle to simulate a splined end for length changes as the suspension moves up and down.

1883740391_DSCN04781.thumb.JPG.a2e6891ee5fa1cf2633f2b3b3c23baf6.JPG

The other side of the transmission showing the "adjustable slipper clutch" on the input side of the transmission

 

895040142_DSCN04801.thumb.JPG.57431273c5a1f165c763c2d27b4f3693.JPG

My eyes and fingers would struggle with those adjustments

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11 minutes ago, maddmaxx said:

How is the oiling in that area?  Is it splash oiling with a hole in the rod to get the oil inside the wrist pin hole?   Drag racing would be different from you kind.  We would just increase the clearance by another skosh.

There is a piston modification that I did not know about. As usual I found out about it after I did a lot of $$$$$ damage. 

20201118_164800.jpg.71968e49029116bbcb277e351b0db433.jpg

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2 hours ago, Further said:

My eyes and fingers would struggle with those adjustments

All sorts of gauges and tools to scale up the tiny adjustments to be more visible to us mortals. 
 

@maddmaxx when I was racing, digital scales were just coming on the market that would do what you are doing and they were spendy. We used tweak bars- same concept, but used a couple low tech levels and a bar on a swivel point. Surprisingly effective. 

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39 minutes ago, groupw said:

All sorts of gauges and tools to scale up the tiny adjustments to be more visible to us mortals. 
 

@maddmaxx when I was racing, digital scales were just coming on the market that would do what you are doing and they were spendy. We used tweak bars- same concept, but used a couple low tech levels and a bar on a swivel point. Surprisingly effective. 

The scale system runs about 130 street price.  Usually a group of racers share one but times are different right now when it comes to meetings in other secret labs.

SKYRC Corner Weight Scale System w/4 Scales & Display Hub

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7 minutes ago, groupw said:

Nice. It would have been about twice that for 4 separate scales back then. 

Tiny Chinese kitchen scales from Shenzhen, the home of all modern electronic appliances.  That's where my son was teaching and he believes that all of our electronics are made there.  :nodhead:

The only problem is that everything from Sky RC is throwaway.  There is no warranty or repair services this side of China.

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