All Day Dan

My Feedback: (5)

The throttle arm that comes with the Walbro carburetor has a very poor mechanical advantage for R/C purposes. Is there a tiller arm available that can be used for R/C available? I understand that the one on the carb can be pried off. Does the spring have to be removed? Dan.

soarrich

My Feedback: (98)

Use a Du Bro nose-wheel steering arm. You'll have to drill it out just a tiny bit, when you do, hold the arm by putting the Allen bolt in and put the Allen bolt in a vice, if you try to just drill the brass out it will start to spin in the nylon arm.

Brillelli sells a nice arm made for this:

http://www.scottellingson.com/brillelli_engines_004.htm

But it might take a while to get Scott's got some health problems right now that are overwhelming him.

You can disconnect the spring, or leave it on, it's very weak, but it keeps the butterfly valve centered so don't take it off or the the carb will wear.

Bob Pastorello

My Feedback: (198)

You also can replace the existing arm with the Blue Hitec servo metal arm, if you have those laying around. THe shaft screw is 4-40, and the servo arm will sit on the shaft nicely. Also permits you to locate it where you need it.

If you don't have those, a standard servo arm will work, too... just use internal tooth lockwashers....little drop of blue loctite. Good to go.

All Day Dan

My Feedback: (5)

Thank you Rich and Bob for the information. It looks easy enough. I'll give it a try. Dan.

JoeAirPort

My Feedback: (41)

Yep I love those Hitec blue arms. I use them on the throttle servo and I have used them on the carb. Works great.

All Day Dan

My Feedback: (5)

OK Joe. Got it. Dan.

C185Pilot

My Feedback: (25)

Can any of you guys post a picture of the Hitec arm on the carb? I guess the splines on the arm just slip over the carb shaft. Does the 4-40 screw go in the end of the shaft? Thanks.

Bob Pastorello

My Feedback: (198)

emailed you

Loopman

My Feedback: (195)

Dan,
The Walbro throttle arm will work just fine if you install a 4-40 ball link. You can then use a standard ball link connector or for added security install a "Sullivan" ball link connector that securely captures the ball. I have also gone with a steering arm set-up as well but find that the ball link route works just as well and does not require "re-engineering" the arm. The option from Brillelli is not a viable one as Scott, for whatever reason, is unable to fill any new orders.

Best Regards

Loopman

BaldEagel

I went with the steering arm option, but instead of drilling it out I squared the collet inside with a small file to fit onto the square shaft of the throttle arm for extra secuity.

Mike

JoeAirPort

My Feedback: (41)

The only issue I can see with using the Walbro arm as-is, is that the distance from the axis of rotation and the hole is very small. So getting a servo arm that short (or preferably even shorter) may be hard to find. You may not be able to get the best mechanical advantage. That's why it's a good idea to lengthen the throttle arm on the carb. You want that throttle servo to travel +/- 45-55 degrees to get the best throttle resolution. I've done this and I get really good throttle control on my gassers.

Loopman

My Feedback: (195)

Joe,
There is no mechanical issue for using a 4-40 ball link on the Walbro throttle arm. I have two set ups as such right now, with no problems. Of course, everyone has a preferred method, mine is just one of them.

Regards

Loopman

Truckracer

My Feedback: (19)

All Walbro throttle arms are not created equal. I believe the ones Joe is referring to has less than 1/4" between the C/L of the shaft and the hole in the arm. To install a ball link this close to the C/L of the shaft makes for a very poor mechanical setup to be operated by a servo. These short arms should be extended as suggested in this thread. Other Walbro throttle arms are a flat plate arrangement with sufficient size to easily accomodate a ball link far enough from the shaft C/L for proper operation.

JoeAirPort

My Feedback: (41)

True, mine are all based on the Walbro WT201B. The throttle arm is way too short to do anything directly.

Loopman

My Feedback: (195)

Dan,
Just for S&G's could you post a pic of the Walbro throttle arm? I'd like to see exactly what we're dealing with. As previously stated all Walbro servo arms are not created equally.

Regards,

Loopman

JoeAirPort

My Feedback: (41)

Check out this thread to see what mine looks like. Not pretty but fasteners are held on with Red Loctite. Won't be going anywhere. The reason it's all cobbed up is that the hole in the short throttle arm is very close to the 4-40 bolt that holds it on. So the hub of the blue servo arm makes it hard to tighten the nut down to something flat. Hence my cobbed up blue spacer.

If you look at my choke arm, that's how big my throttle arm is on this carb.

http://www.rcuniverse.com/forum/m_71...tm.htm#7193756

PS: Sorry my pictures suck...I am getting better at turning off the flash and using manual focus...and not moving the camera when I click.
PSS: I should have just machined off that hub.

krproton

Look at this...

[link]http://www.rcuniverse.com/forum/fb.asp?m=7798315[/link]

JoeAirPort

My Feedback: (41)

Very nice. [sm=thumbup.gif]

All Day Dan

My Feedback: (5)

Thanks Loopman. I had to send the engine back because I could not get it to idle so I can't post an image. Part of the problem was the short radius to the pivot point of the throttle assembly. I did mount a ball link directly to the plate on the carb. The only thing that will do it is a longer arm mounted to the shaft and I'm getting plenty of ideas from a lot of guys.

All Day Dan

My Feedback: (5)

Thanks Joe. It looks good. Dan.

All Day Dan

My Feedback: (5)

Another thanks to you Tim. As soon as I get the engine back I will start the modification. Dan.

krproton

I posted a template for the carbon (or fiberglass or whatever you want to use) in the DL 50 thread over on Giants Flying.

Tim

All Day Dan

My Feedback: (5)

Thank you Tim. I'll go and take a look at it. Dan

gkamysz

My Feedback: (19)

I just happen to be reading this thread today and noted the loctite recommendation with the plastic arm. You MUST NOT allow loctite to come in contact with the plastic arm, it will become extremely brittle. I have seen many plastic parts ruined with thread lockers. Anything from radio switch housings to entire EDF ducted fan rotors failing due to threadlocking compound exposure.

I will try the servo arm idea however.

Bob Pastorello

My Feedback: (198)

Good point, but the risk is completely mitigated if the thread locker compound is kept on the METAL. Slopping that stuff around so there is enough to make plastic brittle means it isn't being used correctly.

You're still right - though - and it's good to point it out.