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Lucero

XV01 won't steer straight

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Hi all, thanks to help on here, the XV-01 Lancia is now up and running but seems to be incapable of just driving forwards in a straight line. The servo doesn't seem to always return to center and adjusting trim is hard because the car never steers straight to start with. The only thing I can think of is the DX5C doesn't like the futaba S3002 steering servo which was the only thing I had from a previous build. 

Interestingly, doing a quick Google of XV01 doesn't steer straight returns an almost identical issue to mine and they too are using a DX5C. Hmm. 

I think the steering sensitivity is too high too but I can't get the car to track straight long enough to adjust it. 

Additionally, and frustratingly, at part throttle the car is kind of ok but then at full throttle it immediately deviates. It's like torque steer. 

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Couple of things to try: whenadjusting trim, don't do it on throttle. Get up to speed by smoothly applying throttle then shutdown and let it coast. You will see if its running straight. Stop thr car, adjust the subtrim in the appropriate direction and go again until straight. If it's pulling on full power, unhook each upright in turn and spin the wheel and make sure all are spinning freely. If one is dragging or binding slightly that will pull under power.

Second slightly more involved thing: Make sure the right height is tje same left to right at each end. It can be different front to rear, but should be the same left/right at each end. If you don't have a ride height gauge, use anything you can put under to check. On higher ride height vehicles like buggies my TC gauge isn't enough so i use lego blocks, but anything will do. After that, on a flat surface like a table or desk, get the car settled then slowly pull up at one end and check the wheels leave the ground at the same time. If they don't, adjust the droop stops until they do. Do both ends. I had this on my FF03 and evening out the droop sorted it right out. 

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Give us pictures. Probably the turn rods are jot the same

lenght. And one wheel goes straight and the other to one side. 
 

second make the wheels look straight with sub trim and then while driving adjust by trim.

 

also you need to keep an eye on tire wear. Use always the same pair in fron or rear. Dont mix 1 rear wirh 1 front And so on

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Keeping it simple, is there any binding in the steering or suspension? Is the servo mounted securely, or did you use those little rubber bushings? Are you using a stock servo saver, High Torque servo saver, or solid horn? Is the AVC on, and if so, is it initialized and adjusted properly? Finally, on a servo tester, does the servo actually center accurately?

The car should accelerate with no torque steer and run pin straight when coasting. Something is wrong; it's probably something very simple but hard to pin down.

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Rebuild your diffs can help, I had this problem twice with an xv-01,  I ran in to my foot on  low speed one time and  then the car pulls to one side on acceleration would not go straight any more , I rebuild the diff could not find a problem with it but it solved it, then a few months later I hit a curb also not that hard and had exacly the same problem again, the diffs are the problem If you hit something, and I don,t no why because there is nothing no damage if you take the diffs apart, but it solves the problem.

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I find Futaba's standard servos like 3002's are too weak for interlinked steering systems.  If on a budget and do not require speed, I recommend the China made cheap $15 20kg servo's sold at Amazon.  They are like violet/pink in color and comes with a 25T horn.  They are by far the best I've used under $20 for lousy and tired steering systems.

I have a fairly generous budget for RC, but some things I just go by experience and not get biased by the cheap price nor the no-brand made in China part.  

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I had/have a issue with my XV-01. New kit built by me. I have built a fair few IC and Elec heli kits in the past and Tamiya kits are no issue build wise.

I built the XV-01 by the manual and got the chassis built no elecs and bunged the on shod wheels on. To check steering geometry etc. Doing this I noticed the rear wheels had odd toe-in. The correct spacers and washers etc was all used,so was the correct pivot pin blocls,differ front to back. I checked everything several times even thought the holes in the chassis bottom might be out. All seem ok. I can not think I am the only guy to get a "faulty" Tamiya part.

Even today the toe-in on the rear ,right hand side is off and can not be altered.Did a search and found nothing. 

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I fixed an issue on my friends XV a couple of months back. His car had a lot of binding in the plastic steering set. So I installed M3 0.2mm shims onto the upper steering bearings and that solved the issue. 

P1170314-1.thumb.jpg.00ad4fe2d04e1ca8e2c963597a187cd6.jpg

Although using aluminum steering set won't have that issue.

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6 hours ago, Gazzalene said:

I had/have a issue with my XV-01. New kit built by me. I have built a fair few IC and Elec heli kits in the past and Tamiya kits are no issue build wise.

I built the XV-01 by the manual and got the chassis built no elecs and bunged the on shod wheels on. To check steering geometry etc. Doing this I noticed the rear wheels had odd toe-in. The correct spacers and washers etc was all used,so was the correct pivot pin blocls,differ front to back. I checked everything several times even thought the holes in the chassis bottom might be out. All seem ok. I can not think I am the only guy to get a "faulty" Tamiya part.

Even today the toe-in on the rear ,right hand side is off and can not be altered.Did a search and found nothing. 

That’s very strange, did you even try different wheels in case one is not true? 

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Did not try new wheels but swapped every corner so to speak ,the issue was always at the rear same corner. never really bothered to find out if the more or less toe-in was the correct, (left or right) made a good job of the shell so it spends its time on show. This issue made me lose interest in it. Tried different arms,up grade pin holders (JJ parts) spacers and washers all checked multiple times. Rear toe-in always odd at the rear. Chassis was placed on paper and holes marked paper then folded on centre line,all are correct. There is some minute play you can use when tightening down BUT not enough to rectify. Never had a problem I could not find,might not be able to fix BUT could always find.Not in this case. I did take pictures from above and its noticeable on squared paper BUT lost the pic now.

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Thanks all some useful info. I'll get a short video of the issue and some pictures. 

Funny you mention steering binding, it sort of knocks when you turn the wheels left/right by hand. 

Servo is mounted on whatever the kit said to use, no additional spacers from memory. 

I'll look into the sub trim option on the DX5C.

I'm using the Tamiya hi torque servo saver. Don't know what AVC is or how to set it up. 

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2 hours ago, Gazzalene said:

Did not try new wheels but swapped every corner so to speak ,the issue was always at the rear same corner. never really bothered to find out if the more or less toe-in was the correct, (left or right) made a good job of the shell so it spends its time on show. This issue made me lose interest in it. Tried different arms,up grade pin holders (JJ parts) spacers and washers all checked multiple times. Rear toe-in always odd at the rear. Chassis was placed on paper and holes marked paper then folded on centre line,all are correct. There is some minute play you can use when tightening down BUT not enough to rectify. Never had a problem I could not find,might not be able to fix BUT could always find.Not in this case. I did take pictures from above and its noticeable on squared paper BUT lost the pic now.

I had that same “issue” on a M05. But actually it was just a optical illusion. 

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Try increasing the frame rate on the transmitter if you can

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On 3/28/2021 at 11:46 PM, Lucero said:

Thanks all some useful info. I'll get a short video of the issue and some pictures. 

Funny you mention steering binding, it sort of knocks when you turn the wheels left/right by hand. 

Servo is mounted on whatever the kit said to use, no additional spacers from memory. 

I'll look into the sub trim option on the DX5C.

I'm using the Tamiya hi torque servo saver. Don't know what AVC is or how to set it up. 

Ball ends could be catching on the chassis, try fitting some droop screws into the front arms to reduce droop by a mm or 2

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I found on the mf-01x that the stock servo arm mount ( plastic ring ) there was enough movement that it would shift the arm a few degrees left on full right lock and visa versa. This causes uncorectable trim issues as it keeps moving. 

Try turning the car on its back. Power on and center the servo trim. Then lock right and back to center to see if its shifting. Then repete with lock left.

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So, not been through all the responses so far but I did spend some time with the DX5C setup. AVC is on and i've desensitised the steering but that isn't the issue, however, it has helped highlight exactly what the car is doing. Basically it can drive straight for about 10 yards then actively changes direction left and left only. Once left, it won't correct again without input from the TX.

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35 minutes ago, Lucero said:

So, not been through all the responses so far but I did spend some time with the DX5C setup. AVC is on and i've desensitised the steering but that isn't the issue, however, it has helped highlight exactly what the car is doing. Basically it can drive straight for about 10 yards then actively changes direction left and left only. Once left, it won't correct again without input from the TX.

Call Horizon Hobby. It sounds like there's an issue with the gyro.

 

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1 hour ago, Big Jon said:

Call Horizon Hobby. It sounds like there's an issue with the gyro.

 

Do you mean hobbywing? An issue with the gyro inside the ESC? Ta

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1 hour ago, Lucero said:

Do you mean hobbywing? An issue with the gyro inside the ESC? Ta

No, Horizon. The AVC is an adjustable gyro built into the receiver.

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On 4/1/2021 at 8:58 PM, Big Jon said:

No, Horizon. The AVC is an adjustable gyro built into the receiver.

Thanks. I've got another SR6100AT here now which I'm going to try.

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