Warbird Replicas Spitfire LF mk IXc

[David Hazell 1]

9 minutes ago, Paul Johnson 4 said:

Mine were from Hobby*£%* but there are pitfalls with using them, without the coiled spring anything but a landing that kisses the ground or a rough strip will rapidly remove them and the mount from the wing.

 

Ouch, ok. I'll leave as is for the foreseeable!!

 

[RICHARD WILLS]

Unless you fly from concrete , I wouldnt bother . Losing the coil spring is a mistake . If you want it to look more scale , hollow out some balsa to make two shells then cover with alluminium ducting tape .

 

[Paul Johnson 4]

Share of some flight video the Mrs filmed.

 

 

[Paul Johnson 4]

Putting out some feelers here guys I have been playing a lot with Fusion 360 and a 3D printer.

I am currently trying to print some tyres to go with the wheels I have created for the Spitfire.

Provided the trials go OK. Would there be an interest out there for a set?

These wheels are designed for a 4mm leg/axle.

The reason being that they have wheel bearings fitted, 2 per wheel.

They are of the early 5 spoke pattern. The hubs are to 1/8 scale but the wheels are 2.75" not the scale 3".

This is to fit Richards Kit.

So Depending on interest and successful trials of the tyre print I would consider doing a small run, run times are time intensive as the 'rubber' material used has a long print time per wheel.

 

 

[leccyflyer]

I'd be interested in a set of wheels Paul - will watch your trials with interest.

 

[Paul Johnson 4]

Obtained some sample material to try as a full reel of material is expensive. The sample was only available in white so my Spitfire will  look a little unusual for a while I trial them.

[Eric Robson]

Yes please Paul,

they would be good for a fixed undercarriage almost invisible in a grey sky.

[Paul Johnson 4]

Fitted to my spitfire and will be flown this Friday.

I HAD to put some black paint thinly on them as white just wasn't right... made me shudder.

The material is as good as rubber and was surprised how good the tyres feel.

There is 3D print lines on the surface but that's to be expected.

 Oh and yes eagle eyed Richard Finn's fire truck is in case of an emergency landing😉

 

If your wondering why the gap in front of the wheel it's because I have changed the pintle angle to give me a greater forward rake and the wheel moves in a forward arc as it descends. I also have mounting pads cut out of 5mm silicone rubber sheet under the retract unit as I don't have the coils in the legs but have oleos fitted.

If your field is rough at all stay with the coil spring legs.

 

 

[Paul Johnson 4]

Oh and it takes 5 Hrs to print a pair of hubs but 9 1/2 hrs per wheel!!

[Paul Johnson 4]

Well, flown this morning, conditions were warm and almost still, just an occasional breath of air in random directions. Being so warm was a little cautious of air density.

Carried out 6 flights all of which had touch and goes so approximately 20 touch and goes and landings. Even with a high ground speed due to little or no wind the new tyres and wheels worked well, with no wind the bearings worked a little too well the Spitfire rolled on forever. I might just make a  miniature anchor to drop out the back for when it's calm.

The wheels show no signs of the printed materials delamination or cracking. The hubs are printed with PET-G so temperature is not such an issue as PLA is, it is also more forgiving in terms of cracking. the tyres are a good fit on the hubs and are a nice snug fit without any signs of tyre rotation.

This shows the tyre construction in the slicer software.

 

This section shows the tyre profile on the rim and shows how well it fits.

The two holes inside the wheel hub are for alignment, this allows the hubs to be printed with the outside faces up to give a better finish. if they were printed in one it needs supports to be used and leaves a  rougher surface finish. Two small alignment pins are cut from the 1.75mm extrusion material and the two halves are superglued into place.

Edited July 15, 2022 by Paul Johnson 4

[RICHARD WILLS]

Wheely nice Paul . I never get Tyred of your beautiful drawings ....

[Paul Johnson 4]

Flew again yesterday early morning, had an one 'intentional' bouncy arrival and all's working great. The only problem was my pilot got out and walked off muttering something obscene about was I watching too many wildlife documentaries about Australia...

 

[Paul Johnson 4]

Been thinking over the use of bearings for two reasons, one the axle must be 4mm, 4mm piano wire is a nominal 4.08mm and will not fit without a lot of fettling down. Secondly the length of roll out on landing. Brass inserts the same size but opened to 4.2mm may be a better way forward. This video shows the length of run with a small push add the weight of the model and its momentum carries it a fair way.

I could make it an option.

[Eric Robson]

Bearings are great Paul if you have brakes, I had a model with bearings in the wheels and it would roll away on our strip which is partly inclined brass tube will be better.

[Paul De Tourtoulon]

I also will go with Eric, I tinkered with my Rafale 18 months ago and fitted ball bearings to my wheels, needless to say on our gravel runway it just rolled past me into the grass, now fitted with electric ( heavy ) brakes.

[Ron Gray]

I would use phosphor bronze instead of brass which can ‘pick up’.

[Eric Robson]

Phosphor bronze is ideal, but bearings would have to be turned from bar stock unless you know of a source Ron. I have used brass rod in the past without problems with a light lube on as our wheels spend most of the time stationary or up in the air. 

[Paul Johnson 4]

I've been looking into both avenues and although bronze is available in bar form and I have a small  lathe it would increase the material/time costs compared to brass tubing.

With adequate use of a good grease it should be a good compromise. I can change the model of the hub to accommodate the brass tube. Also a tube with grease may add to the overrun issue.

[Ace]

When I flew petrol's off concrete, tick over meant they ran on forever until someone mentioned trapping a small length of fuel tubing between the wheel and retention/collet. Simple and the extra friction transformed ground handling. 

[David P Williams]

Paul - grease will pick up dust and grit from your field and turn into grinding paste.

[Paul Johnson 4]

David grease would attract dust etc but only on the exterior as many use a retainer either side of the wheel and this would be where the excess would be although it would only be a minimal amount.

[Ron Gray]

TBH you would be better off with GT85 rather than grease.

[Paul Johnson 4]

Ace you've just given me an idea. Utilising that idea of silicone tubing but... on the tail wheel, I'll modify it and get back to let you know how it works. I'd be nervous about putting too much friction on the mains encouraging a nose over.

 

[Ron Gray]

Sintered bronze bushes, they would do the job and are not that expensive (£2.50?).

 

Regarding the silicone tubing, I use it on my Wots Wot XL to prevent it creeping along on tickover!

[Paul Johnson 4]

Checked out the bushes Ron and price wise about the same as ball bearings but still the same problem of size I could get a 4.1mm reamer to open them up. At least that's a possibility.