Jason1145

Bullhead steering issues

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Bullhead help needed please guys.... firstly... have you guys glued your tyres? Mine came to me unglued and it prevents wheelies as the wheel spins inside the tyre as shown here...

 

I only mention the unglued tyres incase it's a cause of the main problem which is that the truck pulls left under full throttle .... and keeps going left.. right round and round in a circle as shown here... this is with no steering input from me!

Then when you let off the power and the servo centres (as much as it can) it then coasts in a straight line and comes to a stop.

It will drive perfectly straight if you apply low speed at 30-50% throttle only...as soon as you give it the full power it turns left again.

Standard Bullhead with 1 central servo.

It's not too much fun like this after 5 minutes so I would like to fix it pronto, I've spent 3 weeks since it arrived broken and getting it ready for today.

I'm losing interest in the 4 wheel steering as it's quite an effort driving it at any top speed and this was only 2s, god knows what 3s would be like!

Even with the steeeing dual rate  dialled way back the rear still kicks out quite a lot and it toppled over a few times.... I might want to revert to front steering, so anyone know where I can buy rear steer lock outs in the UK?

 

 

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Don't know about the pulling left but to help the rear steering you could mount the rear steering link further in on the servo horn, so that the rear turns less than the front.

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Thanks @Peter_B I did consider that so it's good to have another voice confirm it.

Do you have any dual steering cars yourself?

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I have a clod and a txt-2, both setup for 4ws.

Clod is with a single servo, with a longer servo horn. Txt has the standard servo per axle setup.

I don't get the turning one way, as you describe, with the clod, but it does have a tendency to crab a little.

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@Jason1145,

I've had quite a  lot of experience with clods, having had 3 of them since I was 18. Firstly, I haven't glued the tires onto the wheels on my clod, them slipping shouldn't be an issue affecting the steering, but if you do want to glue the tires just bear in mind that the wheels and tires are quite expensive to replace now. it might be worth putting some elastic bands round the wheels where the beads for the tires sit to improve the grip, but spinning the wheels in the tires will only make the problem worse ……...

In standard trim, the clod does tend to steer from the rear for some reason, the standard servo savers are quite sloppy and a bit cack to be honest. the steering to one side could be caused by having excessive 'toe out' on the rear axle, I'd take wheels off and look at the alignment of the axles when the steering is at neutral. Try and get all 4 axles straight or with a slight amount of toe in. 

If you want to lock out the rear steering, I believe if you have a look at the underside of the chassis where the steering rods protrude there is a small plate moulded into the chassis with a hole in it, you could try putting a ball joint in it and connecting the rear steering track rod to that and then tighten the rear 'servo saver' right up. 

This is what I did with the steering on my sons clod buster and it is a massive improvement of the stock truck steering:

it also gives more clearance between the chassis and gearboxes so you can get more suspension travel.

Don't give up on the clod / bullhead, they are great fun trucks to drive when sorted, and I suspect this problem can be sorted by adjusting the track rods, although I would look at rear steering lockout if you're planning on going 'speedy' with 3S.

PS. it's also worth checking that none of the axles are binding anywhere, especially on the left hand side, as any stiffness might act like having a brake on one side, and with the sloppy state of the stock steering setup, this would have more of an effect than on a normal front steering only car.

Good  luck with it.

 

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11 hours ago, Prescient said:

@Jason1145

Different tension on the sprung front and rear steering link arms?

 

Will check next time it get to the bench. Will have to make sure the lengths are all correct as per the manual.

 

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@MadInventor thanks for the link that looks a very cool modification you made for the Bullhead... was that used in your speed run entry?

My next steps will be to check the left hubs to made sure they spin properly like you said, might have to order some bearings to go in there too while they are apart... more manual consulting to do during little ones nap ;)

Ideally I think if I can get this working by  locking out the rear steering and just using the central servo with a stronger alloy horn it should be good enough for me... that's a 25KG servo only working the front wheels albeit through that darned sloppy servo saver... I could even look at flipping that front saver upside down to get the steering rod parallel to the ground too.

Ive just ordered the CPE rear steer lock out from USA so fingers crossed it's the start of the fix... don't worry I'm not going to give up on the chassis just yet ;)

BTW - you didn't happen to knock out a spare few of those front servo mounts did you haha?

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9 minutes ago, Jason1145 said:

@MadInventor thanks for the link that looks a very cool modification you made for the Bullhead... was that used in your speed run entry?

My next steps will be to check the left hubs to made sure they spin properly like you said, might have to order some bearings to go in there too while they are apart... more manual consulting to do during little ones nap ;)

Ideally I think if I can get this working by  locking out the rear steering and just using the central servo with a stronger alloy horn it should be good enough for me... that's a 25KG servo only working the front wheels albeit through that darned sloppy servo saver... I could even look at flipping that front saver upside down to get the steering rod parallel to the ground too.

Ive just ordered the CPE rear steer lock out from USA so fingers crossed it's the start of the fix... don't worry I'm not going to give up on the chassis just yet ;)

BTW - you didn't happen to knock out a spare few of those front servo mounts did you haha?

Yes, the clod I used for the speed run entry was the one with steering mods in the thread. Didn't make any more of the servo mounts sorry (You're not the first person to ask ;) ). I was thinking about getting a friend with a 3d printer to print a  set (he can only do PLA atm) and see how they fair strength wise. PLA instead of the aluminium, and then keep the steel tubes as steel. Perhaps this is the prod I need to see if he can do me a set.

When I bought my current clod, the previous owner had assembled it with non Tamiya circlips on drive shafts coming out of the diffs, they were slightly thicker, which caused the differentials to be very stiff. That's another thing worth checking is that the diffs are running freely.

 

 

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2 hours ago, Jason1145 said:

Will check next time it get to the bench. Will have to make sure the lengths are all correct as per the manual.

 

Step 24 in the manual. Make sure they are done up fully tight. Spring acts as servo saver and you don't want that with a high torque servo. 

You can adjust without dismantling anything too.

Also glue tyres and use liquid thread lock on the wheel nuts. 

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I bought this Bullhead ideally as a ready runner to get me straight into the fun of it (once I'd put in modern electrics) without me having to become an expert on it straight away.... part of the fun lol

Yeah I did think the diffs would need a check at some point (atleast to put bearings in) if it still pulls left after I've checked the links and hubs etc.

No worries about the front servo mount I was only winding you up about that as I already saw the world and their mum had asked you for a set ;)

 

 

37 minutes ago, Prescient said:

Step 24 in the manual. Make sure they are done up fully tight. Spring acts as servo saver and you don't want that with a high torque servo. 

You can adjust without dismantling anything too.

Also glue tyres and use liquid thread lock on the wheel nuts. 

Gotcha...... 

 

Step 24 - Screw BB4 (3x30mm) needs to have 3.5mm of thread exposed at the top after tightening down the BC2 (3mm) nut

 

I think gluing the tyres will help pull wheelies and improve stopping power as they won't slip over the rims... but now they act like a slipper clutch spinning up to full speed.. and it's easier on the hub fixtures so they won't torque them off... do you think the unglued wheels might cause the pulling to the left? 

I could always try that if the rear steer lock, new bearings and setting correct tensions on the servo savers doesn't fix the problem.. I just need to know the order to try them in. 

1) servo saver adjust as in Step 24

2) Check 4 hubs spun freely 

3) Fit bearings and rear steer lock

Bearing kit ordered!

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16 minutes ago, Jason1145 said:

I bought this Bullhead ideally as a ready runner to get me straight into the fun of it (once I'd put in modern electrics) without me having to become an expert on it straight away.... part of the fun lol

Yeah I did think the diffs would need a check at some point (atleast to put bearings in) if it still pulls left after I've checked the links and hubs etc.

No worries about the front servo mount I was only winding you up about that as I already saw the world and their mum had asked you for a set ;)

 

 

Gotcha...... 

 

Step 24 - Screw BB4 (3x30mm) needs to have 3.5mm of thread exposed at the top after tightening down the BC2 (3mm) nut

At that tightness there is still a lot of spring in the movent and so you want to tighten it more. Essentially at that spring tension with a high torque servo you can hold the wheels and the servo will still turn whilst the servo savers B2/B6 compress and rods & ball ends bend/flex. 

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Do all the tyres spin in the wheels just as easily? If the left wheel spins in the tyre and the right wheel doesnt it will get traction on one side only and drive in circles.

Id be tempted to try glueing the tyres but maybe use something that wont be super permanent. It may not last, but if it proves the issue you could use better glue the second time round.

The rubber band idea could be a good one!

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There are two non-permanent options for "gluing" Clod tires to the wheels, and yes it will help.  First, you can use thick rubber bands around the wheel on the surface the tire bead mounts to as MadInventor said.  This works really well under stock and mildy upgraded power.  Second, you can use either Shoo Goo or E6000 adhesive in 3-4 spots per wheel.  Both of these will adhere well but can easily be peeled off if necessary without leaving residue or ruining the wheels/tires.

I would try this first and see where you're at.  After that you can get into upgrading steering if necessary, but I think this will help a lot.

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FYI the left front tire is backwards in your pic/video above.  Keep an eye out for that if you do decide to glue the tires (don't ask me how I know to look out for this lol).

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Yes all 4 tyres spin about the same as far as I can tell, might well try fixing them at some point too.

One thing I just noticed which none of you could have foreseen because it was a given but one of the anti rotation brackets had worked loose!

Applogies chaps :(

I had replaced the plastic ones with alloy versions before this first ever run and didn't threadlock them in... daft as they both go into metal! 

I'm secretly hoping this was the cause of some movement when the motors got full throttle and ROTATED through the yellow link bracket thing and caused the left turns.

Watch this space for an update next chance I have to run it.

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23 hours ago, Jason1145 said:

do you think the unglued wheels might cause the pulling to the left? 

I think so, only need a to slip slightly more on one side than the other, and it'll skid steer

You could swap the wheels to the other side, and see if it turns right?

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The anti-rotation brackets coming loose could definitely cause your issue.  Tighten them up and secure the wheels you should be good to go.  Also swap that tire around as 3speed said so they;re all running the proper direction.

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Glad to report thread closed...anti rotation brackets were the culprit.

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Nice, glad to see you got it fixed and it was nothing major.

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