1/6 Motorbike / Sidecar

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blythmags
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1/6 Motorbike / Sidecar

Post by blythmags » Thu Jul 23, 2009 10:01 pm

Hi everyone......

Well, I never thought I'd even get this far with converting my 21st Century Motorbike and Sidecar !. Nevertheless, with my limited rc experience and loads of trial and error, I have almost finished the model......HOWEVER..........I have a couple of problems ( thought I would have a lot more) that I cannot fathom out:

1. When I power the transmitter first, then power the model......the steering servo goes beserk, and twists the handlebars of the bike quite violently from left to right

2. The forward motor appears to powe powers the model quite nicely, but when reversing, there doesnt seem to be enough power, as the wheels just about turn in reverse.

As ever, I would be grateful for any advice you may be able to offer.... :?

Many thanks

Best wishes

John

pzrwest
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Re: 1/6 Motorbike / Sidecar

Post by pzrwest » Fri Jul 24, 2009 2:21 pm

What radio system are you useing?

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bobbob
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Re: 1/6 Motorbike / Sidecar

Post by bobbob » Fri Jul 24, 2009 4:51 pm

Just in case you think you are being ignored, a lot of the brains in the club are at the War and Peace show until next week.
http://www.helpforheroes.org.uk/

Never say something in Cyberspace you can't say Face to Face!!

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blythmags
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Re: 1/6 Motorbike / Sidecar

Post by blythmags » Mon Jul 27, 2009 8:37 am

pzrwest wrote:What radio system are you useing?
Hi....I'm using an Acoms Techniplus 2 channel transmitter (27mhz) and a standard Futaba like receiver.

I initially thought that it may be the batteries ?.........but I fully charged these new ones up and the problem is still there. Basically, the servo has a mind of its own and violently shakes from side to side on start up. Also, the reverse movement and ability of the motor is very much compromised....barely enough to move the model...however, the forward power seems ok ?.... :?

Cheers

John

No1_sonuk
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Re: 1/6 Motorbike / Sidecar

Post by No1_sonuk » Mon Jul 27, 2009 10:01 am

The 27MHz gear could be the problem if you live in a high-interference area.

Have you got a servo tester? This is a small electronic circuit that generates the same output signals as an RC receiver. You plug the servo and a battery into it and you can then test the operation of the servo.
If you can do that, it'll serve to implicate, or eliminate, the radio gear as the source of the problem, and at the same time, tell you if the servo is OK.
Alternatively, try another radio setup if you can, preferably 40 MHz or 2.4GHz.

One thing that does come to mind, though:
A while ago, I was making a servo-drive project with a microcontroller project board, and I had erratic behaviour problems with it. I then realised that the I was trying to drive the chip AND the servo off a tiny regulator that wasn't up to the job, so it kept "browning out". The result was a dimented output from the servo as the microcontroller kept resetting.

Now I'm not suggesting you could be suffering from a poorly-designed BEC regulator (which should be able to handle such loads), but it's possible that it's faulty.

WRT the reverse problem, I can think of 3 scenarios:

1 ) If you have a fancy speed controller, it might have a reduced-speed reverse that's not set properly. The servo tester would help here too.

2 ) If your motor controller is entirely solid-state, you might have a problem with the MOSFETs used for reverse.

3 ) If the reverse is relay-switched, the contacts could be dirty.

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blythmags
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Re: 1/6 Motorbike / Sidecar

Post by blythmags » Mon Jul 27, 2009 11:43 am

No1_sonuk wrote:The 27MHz gear could be the problem if you live in a high-interference area.

Have you got a servo tester? This is a small electronic circuit that generates the same output signals as an RC receiver. You plug the servo and a battery into it and you can then test the operation of the servo.
If you can do that, it'll serve to implicate, or eliminate, the radio gear as the source of the problem, and at the same time, tell you if the servo is OK.
Alternatively, try another radio setup if you can, preferably 40 MHz or 2.4GHz.

One thing that does come to mind, though:
A while ago, I was making a servo-drive project with a microcontroller project board, and I had erratic behaviour problems with it. I then realised that the I was trying to drive the chip AND the servo off a tiny regulator that wasn't up to the job, so it kept "browning out". The result was a dimented output from the servo as the microcontroller kept resetting.

Now I'm not suggesting you could be suffering from a poorly-designed BEC regulator (which should be able to handle such loads), but it's possible that it's faulty.

WRT the reverse problem, I can think of 3 scenarios:

1 ) If you have a fancy speed controller, it might have a reduced-speed reverse that's not set properly. The servo tester would help here too.

2 ) If your motor controller is entirely solid-state, you might have a problem with the MOSFETs used for reverse.

3 ) If the reverse is relay-switched, the contacts could be dirty.

Hi.....

Fantastic.....many thanks for your comprehensive reply.....I'll look at the areas your suggest in order to rectify the problem.

Best wishes

John

saracen
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Re: 1/6 Motorbike / Sidecar

Post by saracen » Mon Jul 27, 2009 11:57 am

Another thing to look at on the reversing problem is whether the wheels etc are binding when going in reverse.

Can you remove the motor and try and operate the drive train by hand - in each direction :?:

That would give you a feel for whether there is any difference in the friction going in forwards or reverse.

Adrian.

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blythmags
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Re: 1/6 Motorbike / Sidecar

Post by blythmags » Mon Jul 27, 2009 12:17 pm

saracen wrote:Another thing to look at on the reversing problem is whether the wheels etc are binding when going in reverse.

Can you remove the motor and try and operate the drive train by hand - in each direction :?:

That would give you a feel for whether there is any difference in the friction going in forwards or reverse.

Adrian.
Thanks Adrian...i'll also give this a go....
Cheers....
John

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jdflute
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Re: 1/6 Motorbike / Sidecar

Post by jdflute » Mon Jul 27, 2009 1:00 pm

2nd that on the motor and gears binding John, How did you organize the gears in the end, pics please.
I didn't realise you were on 27mhz, should realy be 40mhz in the uk for land vehicles, and 35mhz for air, however your setup could go digital at minimal cost, why don't you check out a cheap spectrum unit?
One final thought.... did these bikes have reverse????
Jd
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blythmags
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Re: 1/6 Motorbike / Sidecar

Post by blythmags » Mon Jul 27, 2009 1:13 pm

jdflute wrote:2nd that on the motor and gears binding John, How did you organize the gears in the end, pics please.
I didn't realise you were on 27mhz, should realy be 40mhz in the uk for land vehicles, and 35mhz for air, however your setup could go digital at minimal cost, why don't you check out a cheap spectrum unit?
One final thought.... did these bikes have reverse????
Jd
Hi..........Unfortunately, I am unable to send pics of the gears as I purchased an all-in-one motor / gearbox unit. If I have a 2 channel Acoms 27 mhz transmitter / receiver, can I simply switch the crystals to 40 mhz ? (apologies for what may seem to be a simple and fundamental question !). Also too late to check out a Spectrum unit, as I took the opportunity to "seal" everything in the sidecar using a fair amount of epoxy !

Oops !.... :oops:

John

No1_sonuk
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Re: 1/6 Motorbike / Sidecar

Post by No1_sonuk » Mon Jul 27, 2009 3:31 pm

blythmags wrote:If I have a 2 channel Acoms 27 mhz transmitter / receiver, can I simply switch the crystals to 40 mhz ?
No. The RF circuits would need to be retuned.
You can do that to switch 35MHz receivers to 40MHz, and vice-versa, with a range reduction.
However, you can't do that to transmitters. It'll cause damage, and be illegal because the TX will be operating outside its type approval parameters. That's not relevent to 40/35MHz RXs as they don't transmit.

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blythmags
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Re: 1/6 Motorbike / Sidecar

Post by blythmags » Mon Jul 27, 2009 3:38 pm

No1_sonuk wrote:
blythmags wrote:If I have a 2 channel Acoms 27 mhz transmitter / receiver, can I simply switch the crystals to 40 mhz ?
No. The RF circuits would need to be retuned.
You can do that to switch 35MHz receivers to 40MHz, and vice-versa, with a range reduction.
However, you can't do that to transmitters. It'll cause damage, and be illegal because the TX will be operating outside its type approval parameters. That's not relevent to 40/35MHz RXs as they don't transmit.
Hi...........I thought it wouldn't be that easy !

I better try some of the other suggestions

Regards

John

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