Steerable nosewheel on grass?

[Jeffrey Cottrell 2]

Hi Guys, quick question

Just bought myself a second hand Ripmax Bullet at Wings & Wheels. Had a couple of flights, and it flies a treat, so now down to some fine tuning.

First model with tricycle u/c and first with steerable nosewheel.

Spent most of the morning, and some harsh language, trying to get the drive to the nosewheel running smoothly, but however much I try it still drags.

The linkage is fed from the rudder servo, so I'm concerned about how much strain I'm putting on it.

Anyway, thinking do I need the steerable nosewheel at all? I fly exclusively from grass, and all my tail draggers have a fixed tailwheel, so that's the question.

What do you think? Do I need it or not?

Thanks

Jeff

[Andy Stephenson]

A steerable nose wheel makes ground handling so much easier. I always install a separate servo and programming it as a separate function on the radio makes the set-up easier. I use a servo-saver which is a spring that takes out the shock loads on landing. I make my own but you can buy them. The tension is adjustable by compressing the springs between the collets.

 

 

[SIMON CRAGG]

Having had a Bullet for many years..............I never needed or had a steerable nosewheel.

 

Had max throw on the rudder which turned it easily on grass.

 

Added complication in my view!.

 

Good luck, its a great model.

[Nigel R]

Never bothered myself. Up elevator, blast of throttle, she'll turn. 

 

Your mileage may vary of course.

 

[Brian Cooper]

A steerable nose wheel can make ground-handling easier.

 

Where most people go wrong with it is with the amount of movement employed. . . many use too much.

It doesn't require much movement to make a very respectable turn. 

 

With greater movement, the nose can "dig in" and turn the model over. There is also a greater chance of wrecking the servo.

Go for the absolute minimum of movement.... and use a servo saver to absorb the shocks. 

[Nigel Grant 1]

I used a separate small metal geared servo driving the steerable wheel through a plastic snake which seems to protect the servo. Its had a few knocks! I set it up using Mike Holts advice from his writings on Futaba Transmitters. The servo is run through a spare channel on the receiver (5) which is slaved to your rudder channel (4). This lets you set up a lot of expo, on 5, so near the center of stick movement you only get a very small amount of deflection on the wheel, which is all you need as Brian says above. And then when taxiing at slow speed with full deflection you can still turn easily. You also use the sub trim on your spare channel to align your wheel so the model tracks straight as you taxi. 

[Andy Gates]

I do use a steerable nose wheel on a Bullet on grass.

As others have said,it makes running around on the strip much easier.

 

My nose wheel runs off the rudder servo, but the pushrod to the nose wheel is split. The 2 pieces of pushrod overlap and are held together side by side with a length of fuel tube which provides enough friction to hold it all in place until I gets stressed, then the rods slide protecting the servo.

[Nightflyer]

While as others have said on here a steerable nose-leg makes ground handling a lot easier - it is by no means necessary. A lot of Bullets and Tornado's I have seen have fixed nose-legs.

 

From personal experience if you are using a steerable one a standard servo with nylon gears is asking for stripped gears at some point, so either use a servo saver, a servo with metal gears (whether you use the rudder servo or a separate one for the nose-leg).

[Jeffrey Cottrell 2]

Hi all

Thanks for your thoughts on the steerable nose gear. Looks like around 50:50 in favour or not.

Anyway, having spent so much time getting the drive to my liking, have decided to stay with steerable for the time being, and see how it goes.

Couple of thoughts.

Nightflyer

Using standard servo with plastic gear, so I'm doing everything wrong. In my defence, the nosewheel is a 2 1/2" soft foam one, so will introduce some shock absorbing in its own right. Also it is more likely to strip gears on landing than take off, so any issues will show up on the next pre-flight.

Quite like the idea of some sort of servo saver in the system, but can't see how to do one.

Andy.

You described your system with a split pushrod with  fuel tubing connection. Neat idea, but what happens if the nosewheel hits a bump and gets off line during take off.  Means landing with the wheel out of line., or have I got this wrong?

 

Anyway, we'll see

 

Jeff

[Brian Cooper]

For a servo saver ideas, have a look at the ones used in R/C cars. 

[Paul De Tourtoulon]

9 hours ago, Jeffrey Cottrell 2 said:

 

You described your system with a split pushrod with  fuel tubing connection. Neat idea, but what happens if the nosewheel hits a bump and gets off line during take off.  Means landing with the wheel out of line., or have I got this wrong?

 

Anyway, we'll see

 

Jeff

What happens, you either go into the crowd or safety fence,,,

 

 I use Andy's system it's used on car throttles  and brake systems and so easy to set up.

[EarlyBird]

10 hours ago, Jeffrey Cottrell 2 said:

You described your system with a split pushrod with  fuel tubing connection. Neat idea, but what happens if the nosewheel hits a bump and gets off line during take off.  Means landing with the wheel out of line., or have I got this wrong?

 

Jeff I use a thin wire pushrod or a Z bend to give some flexibility sure either will distort which makes taxiing a challenge and in the worst case mean a walk for retrieval.

 

53 minutes ago, Paul De Tourtoulon said:

What happens, you either go into the crowd or safety fence,,,

FUD?

 

Steve

[Andy Gates]

Jeff,

 

The tubing is tight enough for it not to slip during normal running around the field, ie ground handling and take off runs. It works because it is tight enough during the taxi and during take off the load on the nose wheel is decreasing as the plane speeds up.

It does however slip if you land too hard or nose wheel first landing which is where damage to the servo would occur.

[Bruce Collinson]

Jeff,

Let me see if I can describe it without use of graphics.

 

Use a wire pushrod and get hold of two coil springs, two wheel collets to fit the wire, and a pushrod connector, the type which screws onto the servo arm and has a grub screw on top to tighten onto the pushrod.   Modelfixings have them, illustrated, if you can’t visualise one.   Ditch the grub screw, you won’t be tightening the pushrod onto the servo arm.

 

Put a spring and a collet onto the pushrod on either side of the servo arm.   Set the servo and the nose wheel where you want them.   Put each spring into slight compression then tighten the collets.

 

hopefully you can now visualise it, the pushrod is free to pass through the connector on the servo arm so shock loads are isolated by compression of the springs.   Adjust the neutral point by moving the collets.   If it steers like a blancmange on a trampoline, use stiffer springs.

 

It is possible to strip the costs right back by using biro springs and butchering a 13A plug for the screw blocks/collets.

 

I’m sure the two pushrods through fuel tubing will isolate shocks but I cannot visualise it returning to neutral whereas what I have described, as inherited in a second hand Curare (which I have yet to find addictive, not a patch on the late lamented Saphir) seems robust and effective, albeit a slight fiddle to set up.   Shares the rudder servo, incidentally, using the opposite end of the servo arm.

 

Hope this helps.

 

BTW was it you bore the news of DSM kits being brought back to the market?   Any progress?
 

BTC

[Paul De Tourtoulon]

Would a video help ?.

 

[Jeffrey Cottrell 2]

Hi Bruce

Thanks for the extra detail, most helpful. If you look back to Saturday, and a post from Andy Stephenson, which had a picture of the very same system.

Might give it a try.

Paul

Really won't need a video. Thanks for the offer anyway !

As regards DSM models, very much a work in progress. Had an e-mail a while back from Lesley, Dave Smith's wife. He hasn't been to well recently, but she promised to get in touch once he was better.

Asking on behalf of Nick from NJR modelling who plans on bringing these back to market, once we can sort the details out.

We'll see

Jeff

[Andy Stephenson]

I used a couple of springs I found in the spares box, the end collets are cut up from a chock-block type electrical connector. The push rod is soldered to the Bowden cable with a length of brass tube. As mentioned above the push rod connector has the grub screw left out to allow it to slip against the spring tension. This system allows the nose wheel to always return to neutral.

The servo drives from the inner hole on the arm that gives a mechanical advantage which reduces the stress on the servo output, this also gives the very small amount of movement which is all that's required to steer effectively.