Scans of my Lil Wizard rubber band engine mount

Cool, thanks for that. I have been looking for one forever. Thought about making one out of ply and now I have the dimensions!

Ron

Honestly I would love to see someone having these laser cut, including bulkheads, which are identical to the back of the engine mount.

I have a miserable time cutting these accurately out of plywood.

Phil

In my opinion, the Lil Wizard is a bullet proof design unless your flying on asphalt or concrete. Out of all the planes I've even built from yesteryear it's one of the few 1/2A's I have remaining. The design of that mount really didn't save the plane. The ply bulkhead was glued to balsa which faired into the fuse. The balsa now breaks slightly behind the ply. The other problem is that rubber bands exposed to fuel and oil rapidly breaks down. The engine and that plastic firewall now departs when the rubber gives up. This happened to me on mine years back. It didn't go far, but I'm glad it didn't happen when I was in front of it. I found that any of the Goldberg rubber band setups generally were more of a hinderance than a help. This is especially true on the bungee gear setups. Ken

I love the rubber band on mounts. I made quite a few copies. I changed rubber bands periodically. I also always pull on the engine a bit to make sure it is snug. I like the nylon mount best but the ply copy works just as well.

Rolla

Phil that's the nylon mount I have. How are the rubber bans configured and what size bands?

Tinker Terry wrote:Phil that's the nylon mount I have. How are the rubber bans configured and what size bands?

Me, too. Can someone post a picture of the proper way to rubber band one of these mounts. All the pictures I've seen are too distant to get a good idea of the proper banding method. How many bands? How tight? What order is the band wrapped around the tabs? Is it really that important?

The Orderly Mark

Found this pic on hip pocket aeronautics for of a little wizard with the bands shown pretty clearly
http://www.hippocketaeronautics.com/images/control_line_images/cl_lil_wizard.gif

How's this??  Just 2 small rubber bands just wrapped back & forth...

Cheers, Paul

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Tinker Terry wrote: How are the rubber bans configured and what size bands?

You are using a skinnier band than I do. I have been using the same size I hold wings on my RC stuff (#64 I believe). The wider band requires care because it is possible to seal off the intake to the engine!

My technique is exactly the same though.

Phil

pkrankow wrote:Honestly I would love to see someone having these laser cut, including bulkheads, which are identical to the back of the engine mount.  

I have a miserable time cutting these accurately out of plywood.  

Phil

if i can lay this out properly i wouldn't mind cutting some out. not really understanding the dims listed on the pics. also what about the engine mount being cut from delrin instead of plywood? 
one of my toys at work is a laser

3 years later I don't remember what the dimensions listed are...LOL

OK, The pictures are sideways to use.  Paul pictured it in use on an airplane.  The firewall on the plane is 1/8 plywood, there is actually a step in the part the engine attaches to, with the ears thinner.  Without the step the rubber bands choke the engine, and it is very difficult to arrange otherwise.

I would be perfectly happy with 3 pieces of high quality 1/8 inch plywood, some assembly required.

If I had to work from those scans I would use the largest dimension and scale the picture, then measure the picture to the nearest 1/32

Another, possibly better way to get to true scale is to consult the manuals for the bee engines
http://coxengines.ca/engine-and-fuel-guides.html
the holes in the plate match up exactly to the engine dimensions.  Of course the mounting for a bee, and a horseshoe, and others...

This would also account for plastic shrinkage over the decades.

In truth the plate does not have to EXACTLY look like this, just serve the same function, so some liberty in the actual shape of the ears can be taken.

That is a cool toy you have there.

Phil

Paul's plane looks like there is a 1/16" doubler(balsa, maybe?) behind the wing where these fuselages so commonly break. If I built one for a beginner, I would also use 1/32" or 1/64" ply doublers on the front end extending from the firewall under the fairings to back just aft of the wing root. It would be good to use wood glue for weight saving reasons, at least for the rear ones. I'd epoxy the front doublers though.
Rusty

pkrankow wrote:3 years later I don't remember what the dimensions listed are...LOL

OK, The pictures are sideways to use.  Paul pictured it in use on an airplane.  The firewall on the plane is 1/8 plywood, there is actually a step in the part the engine attaches to, with the ears thinner.  Without the step the rubber bands choke the engine, and it is very difficult to arrange otherwise.

I would be perfectly happy with 3 pieces of high quality 1/8 inch plywood, some assembly required.

If I had to work from those scans I would use the largest dimension and scale the picture, then measure the picture to the nearest 1/32

Another, possibly better way to get to true scale is to consult the manuals for the bee engines
http://coxengines.ca/engine-and-fuel-guides.html
the holes in the plate match up exactly to the engine dimensions.  Of course the mounting for a bee, and a horseshoe, and others...

This would also account for plastic shrinkage over the decades.

In truth the plate does not have to EXACTLY look like this, just serve the same function, so some liberty in the actual shape of the ears can be taken.

That is a cool toy you have there.

Phil

i'm going to explore this a bit and see what i can come up with. a side from the laser i have a cnc router table

Lots o' toys then!

Phil

pkrankow wrote:This is a set of scans of my Lil wizard rubber band mount.  The plane is 30 years old.  I measured and dimensioned the images.  They can be reproduced from 1/8 inch plywood.  I have found this mount allows for 2 things, preservation of a trainer in crashes, the engine mount rubber bands "give" instead of things breaking ability to use the same engine on several models with little effort at the field. Enjoy - Phil

Interesting, thanks Phil. I think the set of extra holes is to mount the Testors 049 Red Head with plastic tank mount. There's been other ways, such a what Ace R/C used on their 2 channel Grasshopper trainer. It used #3 sheet metal screws in the sides of the ply engine and firewall mounts similar in concept. Goldberg's method was simplicity, which I like.

Paulgibeault wrote:How's this??  Just 2 small rubber bands just wrapped back & forth... Cheers, Paul

Sharp looking Wizard, Paul. What Cox variant engine is that?

How does this look Phil? About 90 seconds to cut

I would prefer the hole to be markings or very small pilots instead of fully made. Might be me, but I like drilling my own.

The center being left solid would allow for better gluing of the two pieces.

Those look awesome!

Phil

pkrankow wrote:I would prefer the hole to be markings or very small pilots instead of fully made.  Might be me, but I like drilling my own.

The center being left solid would allow for better gluing of the two pieces.  

Those look awesome!

Phil

thanks phil... i was thinking small holes for the next run myself. these may look bigger than they are (.060") and of course the bulkhead does not need hole. next gen coming up!

Great Info!
Thanks Paul,I have a couple of these that were included with an engine lot I purchased and did not know how one would attach it or what kind of model it was from.

Steve

Here yo go. Holes are .020"

Shot of the back so that you can better see the hole size

I like.

Any idea the price?

Phil

I will figure something out price wise.  Since these will be generally used on trainers I will do them for cost of material and shipping. Should be able to stick them in a regular envelope and a stamp. Pm me your address Phil and I would be happy to mail you a couple.

also... what size screws for mounting the engine and what size rubber bands?