DLE 20/petrol engines - remove throttle return spring?

[Rich too]

Make sure to use metal geared servos. Personally I don't use a choke servo, but others do. Secure the prop in the correct position and choke and start the motor following the manual and it should start easily. One of the reasons I like petrol is so that I do not need all the starting gear and start all mine by hand. Have fun, you'll love petrol motors...

Edited By Rich2 on 16/11/2016 13:10:25

[john stones 1 - Moderator]

Yes Andrew don't over think it, as is the case with most things in modelling peoples methods vary, longer arm to reduce current drain sounds like overthinking it, getting a good run and geometry right is what matters for me, as for your battery have plenty Mah and you'll be fine, spring on or unclipped ? both camps seem content, go with what feels right to you.

John

Edited By john stones 1 on 16/11/2016 13:14:54

Edited By john stones 1 on 16/11/2016 13:16:07

[Andrew Cousins]

Metal gears is this due to the extra vibration from the petrol engine??

[Rich too]

that's correct Andrew.

[Andrew Cousins]

Magic thanks

[Ultymate]

Posted by Rich2 on 16/11/2016 12:20:35:

I don't understand the question! What performance issues? The spring does nothing apart from return to idle.

I would not be concerned with battery drain - I've never had problems leaving the springs attached. And the load on flying surfaces would mostly be aerodynamic rather than from the hinges.

The spring does have more than one function, it limits end float on the butterfly and it's shaft. If you remove it totally the butterfly vibrates within the alloy body of the carb and over a relatively short time you'll have a carb that's fit only for scrap. Just leave it connected it'll not overload your servo and in the event of a linkage failure your engine will not go to full throttle

[Rich too]

You're preaching to the converted! I know, I've been leaving mine alone since the first post.

Perhaps, I should not have said the spring does nothing!

 

Edited By Rich2 on 16/11/2016 16:16:09

[Engine Doctor]

Posted by Rich2 on 16/11/2016 16:15:15:

You're preaching to the converted! I know, I've been leaving mine alone since the first post.

Perhaps, I should not have said the spring does nothing!

 

Edited By Rich2 on 16/11/2016 16:16:09

But the spring does do something It stops the butterfly spindle from vibrating and wearing the either the shaft or the carb body allowing air leaks and poor idle settings. ?

[Gary Manuel]

I'm in the "leave it connected" camp due to reducing vibration.

One other factor that I dont think has been mentioned is that the spring has the effect of removing any free play that may be present in the throttle linkage. It will take up any slack right back to the servo gears if the linkage has low enough friction. It should therefore make the control more precise (in theory anyway).

PS - I do completely remove the throttle stop screw. That is the job of the servo at the low end of it's travel adjustment.

[Rich too]

I agree with all of the above!

I leave the idle screw, and use an electronic failsafe/kill switch.

I struggle getting consistent idle and find it easier with the screw. I know most people remove them, and an OS33GT that I got doesn't have one so I'll have to learnt to live with it.

[MaL]

I can't see what the servo quality, or lack thereof, have upon the idling of a motor. There is a mechanical stop on all walbro cards (AFAIK) if you adjust it to give a very low tick over when the engine is at operating temperature and use a 'spongy' linkage so the servo, on minimum trim, jambs the throttle arm up against the mechanical stop you will have a motor that will keep going whilst on the landing approach but not provide thrust to prolong the approach. Fit a kill switch to guarantee you can stop the motor at will and use the throttle trim to a high tickover while flying normally. No resolution issues, no throttle linkage disturbance issues, no need for an expensive servo, just a rock steady solution. I can't remember the last time I had a petrol deadstick.

I must confess I disable the throttle return spring on all my petrol engines, but am at a loss to explain why, as far as I can see it makes no difference, the chances of the throttle linkage breaking is negligible and the motor can always be stopped by the kill switch and the current taken by the servo fighting the spring would be less than a gnats private tackle.