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Old 03-18-2011, 11:30 PM   #1
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Default Please helo setting 2 speed tanny on Yokomo GT4 RTR

Hi i have a new Yokomo GT4 and rtr i bought years ago,and it is not shifting to second gear.I found a little hole in the flywheel with 2 allen grub screws inside and you have to position the 2 wheels the correct way so that the allen key will fit inside (some body that has experience will know what i mean) and i think that is where you adjust the transmission?? to shift sooner or later.

I found that if you unscrew too much that the screw grabs the outer wheel and makes them both spinn together.
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Old 03-19-2011, 03:45 PM   #2
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if the yokomo is the standard 2 shoe 2 speed then you should have a grub screw at the top and bottom opposite each other, these are for setting the gap for the 2nd gear housing to spin freely!
the gear shift screw are offset to oneside, example to the left on top and at the right but underneath.
if there is no rough guide in the instruction manual, then this may take some time, but at a rough estimate screw the gear shift set screws all the way in, then screw both back out 3 turns.
the best way i have found to see if the car is shifting, hold the car by the grab handle, slowly run the throttle up, if the car changes gear you will feel the car slightly kick, if it kicks at the bottom of the rev range turn the screws in 1/8th of a turn both sides n try again, the opposite if kicks right at the top of rev range.
if it doesnt kick at all, try turning the screw inwards 1/4 at a time and retry, can be time consuming but you will get there in the end!
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Old 03-19-2011, 08:26 PM   #3
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if the yokomo is the standard 2 shoe 2 speed then you should have a grub screw at the top and bottom opposite each other, these are for setting the gap for the 2nd gear housing to spin freely!
the gear shift screw are offset to oneside, example to the left on top and at the right but underneath.
if there is no rough guide in the instruction manual, then this may take some time, but at a rough estimate screw the gear shift set screws all the way in, then screw both back out 3 turns.
the best way i have found to see if the car is shifting, hold the car by the grab handle, slowly run the throttle up, if the car changes gear you will feel the car slightly kick, if it kicks at the bottom of the rev range turn the screws in 1/8th of a turn both sides n try again, the opposite if kicks right at the top of rev range.
if it doesnt kick at all, try turning the screw inwards 1/4 at a time and retry, can be time consuming but you will get there in the end!


Ok this is what i found....the other grub screw is to lock the little ring to the shaft that is driving the tranny.

There is only one grub screw that sets the shift timing and how it works is that there is a spring under the screw that gets stiffer and puts more tension on this little basically its like a clutch shoe that gets spit out from the rotation....so if you loosen the grub screw it will take less power from the motor for the clutch shoe to stick out.

My trouble is that the way the manual says to install the ring that has this clutch type thing on it is in a way that with the motor spinning the tranny clockwise...the clutch shoe thing ...lol...is not whipping out like this ( they it is whipping out like this ).....so i dont see how it will be able to whip out.Here is a copy of the manual so you can see

Well it wont let me post a link of the manual...if you have the time to go to Yokomo.com and check it out i would appreciate it thanks.But it does not show what way this little clutch lever sticks out.
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Old 03-19-2011, 08:45 PM   #4
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Originally Posted by matrixman1982 View Post
Ok this is what i found....the other grub screw is to lock the little ring to the shaft that is driving the tranny.

There is only one grub screw that sets the shift timing and how it works is that there is a spring under the screw that gets stiffer and puts more tension on this little basically its like a clutch shoe that gets spit out from the rotation....so if you loosen the grub screw it will take less power from the motor for the clutch shoe to stick out.

My trouble is that the way the manual says to install the ring that has this clutch type thing on it is in a way that with the motor spinning the tranny clockwise...the clutch shoe thing ...lol...is not whipping out like this ( they it is whipping out like this ).....so i dont see how it will be able to whip out.Here is a copy of the manual so you can see

Well it wont let me post a link of the manual...if you have the time to go to Yokomo.com and check it out i would appreciate it thanks.But it does not show what way this little clutch lever sticks out.

While I am not familiar with the two speed in question, a common problem is that it's often stuck in second gear and ppl tend to keep loosening it thinking it wont shift.


You should be able to pry open a two speed 1mm or so with your fingers, if it's sloppy, then you're stuck in second gear, if it's too tight, you may have a sticky two speed. It's unusual that there's only ONE grub screw managing the two speed, but as mentioned Im not familiar with the car or system

Looked at manual, strange clutch with only one grub. It says the GROOVE must be facing towards you.. odd tranny.
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Last edited by blis; 03-19-2011 at 08:59 PM.
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Old 03-19-2011, 08:59 PM   #5
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While I am not familiar with the two speed in question, a common problem is that it's often stuck in second gear and ppl tend to keep loosening it thinking it wont shift.


You should be able to pry open a two speed 1mm or so with your fingers, if it's sloppy, then you're stuck in second gear, if it's too tight, you may have a sticky two speed. It's unusual that there's only ONE grub screw managing the two speed, but as mentioned Im not familiar with the car or system
Man i wish i could show what it looks like.....basically there is a aluminum wheel and there are the 2 grub screws one grub screw locks the ring to the shaft that accepts the engines power and the other grub screw manages tension on this little stick that whipps out under the G force or the rotation..(clockwise)

If you screw the grub screw in then more tesnion will be applied to the spring witch is under one side of the stick...and there fore it will take more RPM to allow the stick to whipp out.....lol.........and when the thing whipps out it grabs the inside of the clutch shoe that mounts after this little ring and engages the second gear as it seems to me....
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Old 03-19-2011, 09:10 PM   #6
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i feel stupid for askijg but i cant remember what % nitro fuel do these cars use?? i have been running planes for a long time and have not touched this car since 2002..is it 10% nitro or 20%
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Old 03-19-2011, 09:15 PM   #7
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i have a feeling he is talking about pretension screws.
some 2nd gear clutches have pretension screws for fine adjustment of the gap between shoe and bell. those screws are located right behind the centrifugal weights on the shoes. so basically the total number of screws in the clutch is 4.
two screws to adjust the gap and two screws to adjust the engagement speed.

my velox v10 has this system but my capricorn doesn't.
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Old 03-19-2011, 09:22 PM   #8
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i have a feeling he is talking about pretension screws.
some 2nd gear clutches have pretension screws for fine adjustment of the gap between shoe and bell. those screws are located right behind the centrifugal weights on the shoes. so basically the total number of screws in the clutch is 4.
two screws to adjust the gap and two screws to adjust the engagement speed.

my velox v10 has this system but my capricorn doesn't.
(Omegaf.. doesnt make sense to me either) Seems like this is a single throw shoe, the other screw is a set screw binding the clutch to the transmission shaft. The pictures in the manual are pretty bad.

Manual -> http://www.yokomousa.com/manuals/gt-4r_manual_e.pdf

Fuel -> 1:10 == 16%

The only other question is ... Does this system use a ballbearing to throw the shoe?

Ok.. and think about this...

If your transmission tension is Looser than the Engines clutch tension, then it will immediately engage second gear becuase the clutch immediately exceeds the transmission's RPM in 1st.. With me?
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Last edited by blis; 03-19-2011 at 09:32 PM.
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Old 03-19-2011, 09:34 PM   #9
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(Omegaf.. doesnt make sense to me either) Seems like this is a single throw shoe, the other screw is a set screw binding the clutch to the transmission shaft. The pictures in the manual are pretty bad.

1:10 == 16%

The only other question is ... Does this system use a ballbearing to throw the shoe?

Ok.. and think about this...

If your transmission tension is Looser than the Engines clutch tension, then it will immediately engage second gear becuase the clutch immediately exceeds the transmission's RPM in 1st.. With me?
Yes thats what i was thinking...i was loosening the grub screw that adjusts the shift timing think that it would get the second gear to engage.But instead i think that the clutch stick thing was just sticking out right away engaging second gear????


There is a ball bearing that looks like a steel ball that touches the clutch horn...under the grub screw there is a spring and under that there is a ball bearing....so that the clutch shoe is able to pivot on it.


And about the nitro fuel....i was using my RC helicopter fuel the last time i ran this car...and it is cool power 30%......is that ok??? the engine was running really good and cool and had lots of power and there was oil pouring out of my muffler still indicating that the piston was getting plenty of lubrication.I think the fuel is 99.8% nitro methane and 30% oil
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Old 03-19-2011, 09:39 PM   #10
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Yes thats what i was thinking...i was loosening the grub screw that adjusts the shift timing think that it would get the second gear to engage.But instead i think that the clutch stick thing was just sticking out right away engaging second gear????


There is a ball bearing that looks like a steel ball that touches the clutch horn...under the grub screw there is a spring and under that there is a ball bearing....so that the clutch shoe is able to pivot on it.


And about the nitro fuel....i was using my RC helicopter fuel the last time i ran this car...and it is cool power 30%......is that ok??? the engine was running really good and cool and had lots of power and there was oil pouring out of my muffler still indicating that the piston was getting plenty of lubrication.I think the fuel is 99.8% nitro methane and 30% oil

It's way too oily and too much nitro for a 1:10. As there is a lot more load on an onroad car, you'll end up blowing your motor up trying to compressed a thick mixture. you need 16% nitro 10-14% oil,

The pictures in the manual are terrible so from what I can make out, tighthen it first and ensure you are in first gear before loosening it. As I said, you should be able to "just" open the clutch by using your fingers, if it's easy to do, you are TOO loose.
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Old 03-19-2011, 09:50 PM   #11
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It's way too oily and too much nitro for a 1:10. As there is a lot more load on an onroad car, you'll end up blowing your motor up trying to compressed a thick mixture. you need 16% nitro 10-14% oil,

The pictures in the manual are terrible so from what I can make out, tighthen it first and ensure you are in first gear before loosening it. As I said, you should be able to "just" open the clutch by using your fingers, if it's easy to do, you are TOO loose.
What about traxxas top fuel 20% is that ok?
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Old 03-19-2011, 10:31 PM   #12
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What about traxxas top fuel 20% is that ok?
It wont hurt, it's more an off road fuel and for larger cylinders I think. Not too lean, not too rich.. should be just smoking at the end of a long straight.
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Old 03-19-2011, 11:11 PM   #13
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I have a question about setting the brakes??? should i set the linkage so that when you release the throttle the brakes automatically apply just a tiny bit??? basically the way i have them set is that with the cars electrical system powerd,the brakes are somewhat applied.

The way my linkage or brake system works is there is a linkage rod attached to the engine throttle and the steel rod that this linkage attaches to and when you squeeze the throttle the linkage rod pulls the rod forward dissangaing the brakes and when you flick the throttle control on the 2 channel radio forward the servo goes the oposite way closing the carb on the engine but also pushing back against this steel rod and engaging the brakes.


I am messing with the brakes to adjust them and found that if i adjust the linkage rod so that its allready kind of pushing on that lever....when i go and apply the brakes of course i get even stronger presher on that rod and the brakes lock tighter...but the brakes are also somewhat engaged when the throttle is at neutral....the car still rolls by hand but there is some resistence and when you apply the throttle a little bit the brakes dissengage
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Old 03-20-2011, 07:59 AM   #14
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ok i had a look at the manual. i think i understand what is going on now.

the clutch comes preasembled. the screw that is offset is used to control the engagement speed. the other screw that rests on the centre is actually what holds the clutch to the shaft. so screw that one down as tight as you can.
make sure that it is aligned with the tooth on the shaft in case it isn't anymore.

once you got that right, then go ahead and tighten the offset screw to tweak the clutch speed.
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Old 03-20-2011, 02:28 PM   #15
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ok i had a look at the manual. i think i understand what is going on now.

the clutch comes preasembled. the screw that is offset is used to control the engagement speed. the other screw that rests on the centre is actually what holds the clutch to the shaft. so screw that one down as tight as you can.
make sure that it is aligned with the tooth on the shaft in case it isn't anymore.

once you got that right, then go ahead and tighten the offset screw to tweak the clutch speed.
Yeah basically picture this since you cant see the mechanism unless you are face to face with it.

The clutch body that is held onto the shaft by the one grub screw? has this little claw and there is a pivot on one end...picture a stick and on one end of it there is a hole at the one end and a pin going through it....there is a slit on the outer face of the clutch body and the stick rests inside flush with the outside of the clutch body......this clutch shoe though is shaped to a slight C....so it confirms to the round shape of the clutch body


On the end of the claw where the hinge is there is a spring undernieth that puts pressure on that end depending on how tight the grub screw is screwed in under the claw....and under the extreme clockwise rotation the other end of the claw that has no pivot gets wipped out and touches the inside of the clutch bell that goes on after the clutch wheel or body.


What i dont get is that the way they tell you to mount the clutch body....allows the claw to lift up under extreme clockwise rotation...basically while spinning clockwise the clutches claw is faced and lifts up like this...(
i would think that putting the clutch body on the other way and allowing the claw to whipp out like this would work better under rotation ) as the clutch body is spinning clockwise i would think that the claw could only whipp out this way ......)............but they say to put the clutch body on so that the claw will whipp out this way (....so basically it has to lift up????? does that make sense? instead of it whipping out?


If the part of the claw that does not have the hinge is facing the way of rotation then how can it lift up...i would think it would suck down to the clutch body even harder and not come out
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