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Tamiya F104 Pro!

Old 07-10-2017, 12:46 AM
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About the diff; counting turns is not the way, the springs and bearings are too inconsistent to make a decent assumption. I'm working on a measuring gauge, but you simply keep tightening untill you can race without slippage. I do 1/16 turns (22.5 degrees) at a time, at the most.

I run 1.9, 64 or 48p does not matter. Just go to a LHS and mix'n match gears. I now run 64p with a Corrally spur and some hardened alloy pinion.

Good luck,

Hugo
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Old 07-10-2017, 05:10 AM
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Some of the British Xray guys use a mini torque wrench to set the diff. Im not sure of the brand but they might be able to let you know on the Xray thread.
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Old 07-10-2017, 05:19 AM
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Here's my first try at measuring slip-torque:

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.


I locked the pinion and spur my placing a second pinion. I just wanted to know what range I'm working with, my next device will be a usable tool, I hope, using a load cell and maybe an electric motor to drive the left wheel at a constant speed.

Hugo
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Old 07-10-2017, 02:33 PM
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Thanks for the replies

I'm also running the 104w at my local technical track

I have these arms as spares, anyone know where they're orig from and will they work? I think they're a narrow setup
Attached Thumbnails Tamiya F104 Pro!-img_6925.jpg  

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Old 07-10-2017, 02:46 PM
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Originally Posted by HugoW View Post
Here's my first try at measuring slip-torque:

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.


I locked the pinion and spur my placing a second pinion. I just wanted to know what range I'm working with, my next device will be a usable tool, I hope, using a load cell and maybe an electric motor to drive the left wheel at a constant speed.

Hugo
Like Rob said, use a torque wrench

Husky 5-80 ft. lbs. 3/8 in. Drive Digital Display Click Torque Wrench-H3DTWDIG - The Home Depot
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Old 07-10-2017, 02:52 PM
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Originally Posted by Djchow85 View Post
Thanks for the replies

I'm also running the 104w at my local technical track

I think I have standard 104 fronts in my spares box, maybe worth switching it up to get quicker steering?
I used a lot f104...
X the front end let's try team saxo...it have some tolerance (too much because is made of plastic) but it works...better response...
for the diff i used the thrust ball bearing from f103 instead the standard inner ball bearing...
it is a lot better...if the diff is new with ceramic balls the base setting I think is all tight less half/ three quarter of a turn...when diff will become older you can try three/quarter-1 turn less from the maximum tight...
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Old 07-10-2017, 04:06 PM
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I dont fully understand, you mean use team saxo front end? Do you have a part? I'm wondering if 1/4 turn from full lock is not enough (as the manual prescribes). I find I'm slipping (straight line) in one area when coming out, lacking forward bite. Maybe I'll try a bit tighter...

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Old 07-11-2017, 12:06 AM
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Originally Posted by astgerma52sp View Post
Ehm, no. I measure a slip force of 100 grams (about 1N) at 0,2m arm. That means 0,2Nm torque. The one you like measures a minimum force of 6.78Nm, about 34 times higher than the value we need.
If you use the torque wrench to set the tensioning nut to a specific value to control slip, I doubt that is a measurable constant with the tool specified.
I have not found torque wrenches in that are accurate in the range we need so set diff slip. If you have, please post.

Cheers,

Hugo
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Old 07-12-2017, 09:37 PM
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Adjustable Torque Control Scrwdriver, 1/4" Hex, .2-1.2 Nm

There are certainly calibrated tools available to any accuracy range you want, with enough money, but the thing most people miss is that the extremes (especially low end) of the advertised range are not going to be accurate. For example, if you need to torque some bolts to 10ftlb and you use a wrench whose range is 10-200ftlb, you are going to overtorque those bolts because the mechanism just doesn't provide reliable stoppage at the low end.

Many wrenches are rated as accurate from, eg, "20-100% of full scale", so the example 10-200 wrench wouldn't even start meeting its accuracy range until you were above 48 ftlbs (IIRC). They just label it 10-200 because those are the marks they engraved on the adjustment collar. Even that expensive screwdriver I linked probably wouldn't be reliable at .2, but it was the first one I found.
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Old 07-13-2017, 12:07 AM
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Seems like a waste of time to me. Just make sure the spur gear doesn't turn at all, when holding both tyres and trying to turn spur gear by hand. That would be the minimum tightness. From there just adjust to suit. Make sure you recheck from time to time, especially after a rebuild, as the diff does loosen up a bit.

A slipping diff is a nightmare in my opinion, as it always means slow acceleration, too much corner entry steering, and understeer mid corner/ext.

Mike
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Old 07-13-2017, 01:33 PM
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Most of the time a non slipping diff is correct, as posted above. Sometimes, if the track is garbage, you have to let the diff slip. There were videos of a Tamiya nats where one of the top qualifiers had his diff just screeching from slip all the way around the track. I was not there, but I heard the track did not have much grip that weekend.

One of the first Tamiya nationals I went to one of the guys had his pit man on the track adjusting the diff during hot laps. He did have the old F103 diff on there. Same thing, we had to run the stock F104 rears, which were pretty low grip.
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Old 07-13-2017, 02:24 PM
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Originally Posted by ixlr8nz View Post
Seems like a waste of time to me. Just make sure the spur gear doesn't turn at all, when holding both tyres and trying to turn spur gear by hand. That would be the minimum tightness. From there just adjust to suit. Make sure you recheck from time to time, especially after a rebuild, as the diff does loosen up a bit.

A slipping diff is a nightmare in my opinion, as it always means slow acceleration, too much corner entry steering, and understeer mid corner/ext.

Mike
It should give some. But, it should be hard to make it slip. If you are a complete gorilla is it possible to have a nearly locked diff and the car will not rotate at all and the diff will still be smooth as silk. If you run in the diff by holding one wheel and running some throttle then switch sides, about 30 to 60 seconds a side, the diff is hot and should be bedded in. I then do a trick an old 12th scale guy taught me. Put the car on its left side, pinning the left wheel down. Now hold the spur. Then Turn the right wheel. You should be able to turn the wheel smoothly and feel the give/slip on the spur. It should take a decent amount of force to turn the wheel, but it should be smooth and not grab or be jerky. Then set the car on the track in a high grip section and blip the throttle, go up by 1/8 turn at a time until you stop hearing the diff bark (if it barks at all), then back it off 1/8 turn. Now it's set for the traction and not for how it feels in your hands.
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Old 07-13-2017, 04:50 PM
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has anyone converted their 104W to standard narrow front? I looked at the upright link and shaft and they seem of different design.. maybe not worth the change?
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Old 07-14-2017, 08:58 PM
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Originally Posted by Djchow85 View Post
has anyone converted their 104W to standard narrow front? I looked at the upright link and shaft and they seem of different design.. maybe not worth the change?
Its a simple change. You will need an f104 front arm plastic parts set, a pr of f104 king pins, a pr of 35mm turnbuckles, a package of ball nuts and 2prs of 5x10 bearings. All in its about $25.- to convert to a legal width.
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Old 09-01-2017, 07:31 AM
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Oooh, good diff setup advice... I'm going to try that at the track today.

So I finally got to drive my F104w

I'm running the car on "room temp" street pavement.

The car off power, pushes. Reasonably, but pushes. On power, the car is pretty difficult to deal with.

The car can break the tires loose at roughly any speed below 15mph. So acceleration is takes a lot of care not to have the back end want to chase the front.

I have the HobbyKing X-Car 45a brushed speed control. Any time I get on the brakes the car wants to come around.

Should I be using a loose diff setting as traction control to help the acceleration and braking issues?

What's a "good place" to start with for putting oil on the kingpins? How about the damper pad? I bought a RM-1 shock, and will be putting that on tonight. I have the stock fluid in it now.

I also picked up the 1.3, 1.5, and 1.8mm 3 racing t-bars to provide some tuning there.

So... what's recommended? I'm all ears.
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