DIY– Puncture Free Tyres This project is very much an experiment that some Catapult sailors may be interested in. Pop back here from time to time for updates on how these DIY “puncture free” tyres perform. The article publication and amendment dates are at the foot of the last page. History - I'm not a big lover of the solid launching wheel tyres on a Catapult, so I fitted a set of 10 inch wheels with inflatable tyres which are; lighter to carry, float, and are kinder to the boat frame over rough ground. After only a few months of use a fellow Catapulter pointed out that one of my tyres were coming off the wheel rims. Both were! All I could do was to reduce the pressures. But in use, the lower pressure allowed the tyres to creep around on the rims. This in turn pulled on the inner tube valve stems and made the tubes leak! As an aside, I also experienced leaks with a pair of, old perished tyres that I'd just fitted on my prototype Catapult Axle: See “Sand-friendly Auxiliary Wheels” on the Repairs and Mods Page - (Return to Repairs and Mods Page) As a short term solution I refitted the original solid tyres. Long term solution? Buy better quality pneumatic tyres and tubes, or buy two more wheels complete with pneumatic tyres again. Feelings of Deja Vu were raised. Rather than investing in more pneumatic tyres, I pondered over buying some more expensive (Foreground) My 10 inch tyres were so loose on the wheel that were “puncture free”. wheels that I simply removed the inner-tubes and injected These might be the solution: But foam through the valve holes while rotating the wheels would they be more forgiving inside the tyres. The rather nice “Dog” sculpture was excess foam escaping from the empty valve hole. over rough ground than the solid wheels? Would they float? – How For tyres that are tight on their wheel rims, like the16 inch heavy are they? I don't know!!! one behind it, follow instructions in the text. Anyway, long story short, I did a web search and found some 'You Tube' videos showing DIY foam filling of various off-road tyres. Some methods seemed successful, others were rather hair brained and bodged, but none had any long term follow up.

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Curiosity got the better of me at this point and I decided to buy some cans of expanding foam (Gun Grade - for my foam gun), and give this tyre filling thing a go. I'd nothing to lose as my 10 inch tyres were too loose to reuse, and my 16 inch ones were ancient. Would the foam take up the slack in the 10 inch tyres or would the tyres still move on the rims? Would the foam just crush up in use? Only a trial would answer these questions! PLEASE READ all UPDATES at foot of page BEFORE CONTINUING If you fancy a go at this yourself and have a future use for expanding foam I suggest that you buy a foam gun rather than using the self dispensing cans. A dedicated injection gun is well worth the money (at about £15) as it's far more controllable, cheaper long term, and you can save any unused foam with minimal gun cleaning afterwards. Gun Grade “No Nonsense” foam is currently available for about £4 per 750ml cannister- which is enough to fill two 10 inch tyres. The larger volume 16 inch tyres (the ones on my Auxiliary Wheels) consumed about two thirds of a 750mm cannister each. Don't forget to buy some gun cleaner.

Mess warning! The foam is extremely sticky and gets everywhere. Wear gloves and old clothes. Cover up the working area and have acetone or cellulose thinners to hand to remove uncured foam. Once cured, only a special solvent will remove it. Wear eye protection in case any foam spits out under pressure. OK! It's really simple. First. You need to accept that your tyres, and probably the wheels, may be scrap if this goes wrong. It may just 16 inch wheel just after foam injection. be possible to salvage a wheel, or even the innerThe drilling method should work with the 10 inch wheels as well, but will sacrifice your inner-tube to be buried in foam. tubes, but the tyres will be beyond further use if you Drilling is much simpler and quicker than trying to get a tyre seated back on the wheel without an inner-tube to help inflate drill them. it. Disclaimer;- Don't sue me if this goes wrong - you're on your own! Remove the valve core from the inner-tube and use the suction end of an air bed pump to suck all the air out of it. I suppose you could get close up and intimate to suck it out if you feel brave enough. Screw a dust cap back on quickly to stop air

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getting back in. This will keep the inner tube flattened inside the tyre and should hopefully keep it out of the way during the next stage. Drill about eight 10–12 mm holes equally spaced around the tyre in the mid line of the tread. If you barely drill through the tread thickness you should avoid catching the innertube with the drill bit. I used the moulding lines across the tyre tread (just visible in the photo above) to space the holes equally around the tyre. The holes in the tread area should also let any water run out in use. The foam is bound to 'squash' a bit in use, so some water is going to get in. Filling the Tyre. Apparently putting some water into the tyre before starting to foam fill it will help with curing and adhesion. Give your can of foam a really good shake, then inject foam for about 4-5 seconds at a fast rate deep into each hole in turn. Clean the nozzle exterior and leave the foam to expand in the tyre for at least 10 – 15 minutes, then repeat with less nozzle depth. Continue this sequence until all the holes are bubbling foam out. Use the leakage from adjacent holes as a guide to when it's full. I suspect that leaving the foam to cure in layers between injections will save on the amount of foam used and allow better curing. So you could leave longer between injections. Cleaning up. Attach the small nozzle (supplied) to the gun cleaner cannister and use it to spray the top of the foam cannister and the gun immediately after separating them. Remove the nozzle and attach the gun cleaner to the foam gun and spray a couple of short bursts to fill it. Leave to soak for 15mins, then spray again. Remove and store the gun. Leave the filled tyre laid flat for 24 -48 hours. Don't leave the wheel stood upright as this will leave a flat spot on the tread. The foam takes a long time to cure in the middle of the tyre; Mine was still un-cured inside after 24 hours. I found out when I had to re drill a small area that hadn't fully filled and the drill bit came out with uncured foam on it. Finally break off any the expelled foam and clean up the tyre. If you feel any soft spots around the tyre, just drill into them and top up with more foam. Once fully cured, place some body weight on the wheel and roll it on smooth ground to check for even filling. You'll feel some initial squashing of the foam. This may leave the centre part of the tyre tread feeling a little soft or loose. I'm hoping this won't be a problem. It's only a light boat. Time will tell.

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Note. There are various methods to inject foam that can be tried, but if you choose a method that involves breaking the tyre's bead from the wheel rim you may have trouble getting it to re-seat, even with liquid soap on to help. Foam expansion pressure alone is unlikely to re-seat it. Usually it needs a very high volume of air from an air tank. Tyre after 24 hrs. curing. Foam escapes from little cracks everywhere. This ancient rubber was in a bad way!

Cleaning help - Spray some silicone onto the outside of the tyres before foam filling. This may prevent any escaping foam from sticking. The foam comes off the plastic wheels OK, but it sticks to the tyres and marks them. If you decide to try foam filling, please feel free to let me know how it went, what type of foam you used, and what results you had. Or, if you have any questions, don't hesitate to contact me - [email protected] Note, I understand that the disposable foam dispenser/guns can be reused if you clamp the very end of the tube between a couple of small wooden blocks until needed again. Then just cut off the crushed pipe end to reuse the foam. It might work! ............................................

UPDATES UPDATE 1 - My first trial of the foam filled wheels was at the Grafham Cat Open. The 10 inch wheels initially seemed promising, but after holding the boat's weight stationary for half an hour they developed flat spots. “Bump, bump, bump”, etc. in use. The 16 inch wheels, on the auxiliary axle, faired better- but they weren't left holding the boat's weight for long. They flattened slightly all around the tread contact area, I expect these would also develop flat spots if left with weight on. Overall, a disappointing experiment. I've salvaged the 10 inch wheels and tyres to fill again with a different foam type, assuming I can obtain any. I'll report back here after more testing next season, 2015. Probably just after Bassenthwaite. UPDATE 2 – I have removed the crushed foam filling from the 10 inch wheels and (Return to Catapult Home Page) (Return to Repairs and Mods Page)

managed to salvage the wheels and tyres. (photo below) New inner-tubes were bought to replace the ones with damaged valves caused by tyre creep. Read on...

I gave some thought to the original problems of tyre creep and tyres coming off the rim, and decided to resize the wheel rims using narrow strips of 3mm thick vinyl floor covering (light brown in photo below). This enlarges the wheel's shoulder diameter from 3.75” up to 4.00” and makes the tyre fit snugly on the wheel and avoid the tyre creep that wrecked the original inner-tubes. The strips are stuck in place using EvoStick impact adhesive. This mod was highly effective!

Packing strip glued in position on wheel shoulder.

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I also bought a new set of 10inch wheels complete with inflatable tyres. These wheels came with a set of 20mm needle roller bearings fitted. (which I didn't ask for and didn't really want!). A quick release of all the air pressure in the new wheels and tyres revealed exactly the same problem of oversized tyres supplied and fitted to undersized wheels. The tyres were clearly very loose on the rims . This meant that these tyres would also creep around the wheels if low tyre pressures were used to absorb the bumps! So the new set of wheels have also been modified (shown above). •

It looks like foam filling is a failure unless a more spongelike foam can be found. Answers on a post card please...See update 3

•

The vinyl strips as wheel spacers have resolved the 10 inch tyre creep problem that seems to be universal with the cheap wheel and tyre sets.

I'll keep the article updated, but at May 2016 all is well. UPDATE 3: At the end of the 2016 sailing season, I noticed that my tyres treads were de-laminating in places. Clearly these would fail in short order. So I can no longer recommend purchasing the cheap tyres off eBay. The modification to the wheel rims, above, (to make the tyres fit properly) has been a success though. So with better quality tyres all would be OK. I noticed that Stuart Ede, our club secretary, was using some commercially produced 10 inch puncture free wheels that he had bought off eBay. These seem to come with ball race bearings fitted, which could be used in fresh water conditions, but would not last long in sea water. But modified, these may be ideal. I've bought myself a pair of these, and found it very easy to tap out the steel ball race bearings. I then bought a 250mm length of 30mm diameter solid Nylon Rod, off eBay for £6.50 inc delivery. This was cut to length and drilled down the centre (pillar drill required) then fitted into the hubs to convert them to plain nylonbearings. Search ebay for Solid Rubber PU Foam filled Truck Wheels.(£17a pair free del) A filler piece of plastic drain pipe was also used in the hub to improve the fit of the nylon rod. The rod was then inserted into the wheel hub. Use silicone adhesive to set it in place. This prevents rotation of the rod and keeps moisture out. I also pressed Converted wheels take standard 8mm bolt now.

some sealant between the tyre

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edge and the wheel rim to keep water out. Wheels now suitable for all conditions. The wheels I ordered were shown comprised of two halves bolted together - but the ones received actually seem better for resisting water ingress and rusting. You could check with the supplier before ordering. I'll give these a trial during 2017 and let you know how they perform. Drilling the centre hole accurately through the nylon rod proved difficult, even in a 3 inch length (1.5 inches from each end). The drill needs feeding in slowly, and pulling back frequently, to avoid jamming. (A stationary drill in a lathe may work better). If these wheels perform and last, they would seem to be an ideal solution. Other colour wheels are available.

Revisit the article again for updates. Syd Gage - Catapult 506 First published October 2014 Last update December 2016

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