Take Off Dolly

[Tim Mackey]

pics

[Erfolg]

Tim

That is a simple looking trolly. I am correct in thinking that it shows a wing strut to restrain the model on the trolly, until it lifts off?

I have now pretty much reached a stage of completion.

The picture above shows the inclusion of the front restraining wires. Although it was my intention not to cover with heat shrink, it proved necessary. The reason being my lack of attention to good trade practise, in not using vice grips.

I have tried the trolley in my garden. I am not sure in my own mind how it compares with the grass at our flying field. The grass is certainly far lusher. Now has very few weeds, having been ruthless with summer and autumn lawn treatment, and countless spot weed killers. Although I am somewhat annoyed at a hole that a squirrel has dug in the lawn. Unfortunately my cat died this year, which kept out squirrels, and I thought he had no practical use.

What has surprised me is how fast i can get up to, in approx 40 feet. In some ways encouraging, in that the model stayed on the trolly. It was also possible to steer quite effectively initially. There was one reservation, that when going quite fast, steering caused the model wing to slide across the foam. From practical operations at the flying field, it is during the earlier, relatively low speed part of the run that the model can need steering. Once at speed, they seem to pretty much run true. However there is a difference between a trolly and UC, that is, as the model goes faster, the load on the wheels lightens, with the trolley, the weight of the trolly is always acting on the ground.

[Erfolg]

I have been looking at RW link to Richards video.

The lateral pegs on his trolley or something similar could be needed as per the video. Although it seemed that my model wing moving side ways was a consequence of my deliberate weaving to test control, at some speed. Which even on reflection seems very good, I hope that this is more than rose tinted glasses.

What surprised me is that compared with the video, I seem to have reached a similar speed, at least once. Of course I am now thinking why did i not take off, although is certainly something which I did not want, as that would have been a real disaster.

I think all in all, I am feeling more confident than I did, particularly with respect to the tailwheel. All though I still have concerns that will all be as well going much faster, that I expect to do for a take off with a good margin for safety.

[Chris Bott - Moderator]

It looks good Erfolg. I think the only thing you haven't tested is that the wing can reach, or is sitting at, a takeoff AOA.

It looks like the elevator will have no chance at all of lowering the tail. Hopefully that won't be necessary.

[Erfolg]

Oh yes I have!

As the speed increases the tail rises. which i kept down with up elevator.

Given the speed i got the thing up to, I did have some concern that it could take of. Later I did have greater concern that I had pushed things a bit far, particularly after looking again at the linked video. At the time I was more concerned in running into the fence. Perhaps stupidly, I was also pushing hard to see if the trolly was stable when steering, these suggestions can take on a life of their own. Even now I still have a concern that the suggestions has some validity at model speeds. I spent some time thinking how I could drive the trolley to check the directional stability whilst steering.

I have just had a thought, it could be some time before I can test it in the real world. This is most unfortunate, in that my anxiety will probably increase, as to will it operate correctly in a platform to launch a model and is capable for allowing adequate directional control.

Edited By Erfolg on 22/09/2015 22:48:01

[Erfolg]

My dolly has been tried, with much lower levels of success than in my garden, at the flying field.

To save any valued models from destruction I used an old GWS Texan.

I placed the Texan on the trolley, I tried a quick roll. only to find it essentially did not. A push resulting in an inch of two of roll, at best. The grass on the field is pretty short at present, although the ground is already very wet. I observed whilst stood very close while my Test Pilot attempted a take off. The nose rotated forward and somehow the model came of the trolley. The trolley stayed where it was, fixed as a rock. The model was returned, some up held in and the throttle opened up again, once more I was omnipresent. This time the trolley moved forward all of 100 mm, the wing LE was seen to rise up the bicycle spokes, clearing the top of the spokes the model leapt into the air and was gone. All pretty fast.

Now I can conclusively state, with absolute conviction, there was no issue with steering or instability of the steering or the back end in any form. .

The flight did culminate with the fire wall coming loose on the model and had to be landed.

At present I intend to take the process forward in two or three stages, as follows

• Attach the model to the trolley to prevent it leaving (taking of), then to undertake some high speed taxing, to see if there is any instability issues.
• The second stage is to bend the spokes to a more vertical position, to see if it is the slope of the arms is the issue.
• If stage two indicates it is not the slope that is the issue, i will try to find some longer spokes and make some longer arms.

Edited By Erfolg on 28/09/2015 17:14:23

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Edited By Erfolg on 28/09/2015 17:18:58

[Erfolg]

Stage 1 of the test process has been successfully undertaken. The trials took place in the local park with the model secured with rubber bands.

To be sure that the test was undertaken in a thorough manner I had set a number of steps under various conditions/scenarios to see how things went.

• model operated with a fixed tailwheel,a) firstly straight runs b) then using various amounts of rudder until full rudder was used under full power.
• With the trolley control activated, a) just taxing b) straight runs, with power levels up to full power c) Straight runs but with deliberate moderate steering, up to full power. d) Up to very fast (flat out) running, whilst deliberately lifting the tail, whilst running straight. e) the same whilst steering, up to deliberately exaggerated steering.

I can say with 100% confidence that at model speeds, which were possibly 20, maybe 30 mph., that is above take of speed, that there is most defiantly no issues with rear steering.

I did manage to get the whole caboodle running along with the trolly tail wheel of the ground, with the main wheels braking ground intermittently. Impressive as it was to me, I thought that it would be far nearer to being representative if just the rear wheel could be seen to skipping/braking contact with the ground. Even under what i considered to be severe provocation, there was no instability with the set up, even quite tight turns , although more representative putting alternative left and right inputs, and also runs with double inputs in the same direction.

I have one regret, why can I not have this set up to fly

I am totally confident that rear wheel steering issues are not an issue at our speeds and scale. One more dragon has been slain!

Now the issue is the premature release of the model a product of either the rake or the height of the guiding spokes? I know this is definitely that others know two things, which I hope they will share.

• The angle of the rake
• the height of the restraints