Tethered car builds

Home Updates Hydros Cars Engines Contacts Links Contact On The Wire

Lament from a locked down workshop

Planning for the 2020 season started way back in November, as there was so much in the offing. Retro Club track days, Opening of the Buckminster track, swap meets, Old Warden, International tethered car and hydroplane events and then some normal family pursuits. All hotels and travel booked by the end of Boxing Day and a whole list of jobs to finish before it all started, rather than a last minute rush. Get stuck in early and get everything prepared, projects completed and any outstanding ‘roundtuits’ knocked off. A degree of self-satisfaction was in order when the list was cleared, although there was a last minute addition with the news of the official opening of the Buckminster track scheduled for May. The kits for the Redfin car were still not available but the engine bought some months before had to go into something for that event, so a quick distillation of ideas and a few sketches and that was on the way. News started filtering through about the northward track of the virus and as the spread worsened there was advice from BMFA and MPBA that flying and boating could still go ahead, but no mass gatherings, and then the news from all the national and international authorities that every model activity was to cease. On top of this the lockdown put the kybosh on the last remaining plans, leaving the bench clear, the list clear and nothing on the horizon. No builds, repairs or renovations in prospect, all cupboards and shelves cleared, tidied, parts sorted, and er nothing, and with the ban on travel, no possibility either of helping out fellow enthusiasts by relieving them of some of their unwanted stock.

With no prospect of any activity for the foreseeable future, no projects lurking and ebay not providing any opportunities it was time for desperate measures and a search of all the boxes and drawers in the garage, loft and workshop to see if there was anything that could be pressed into service? What an odd selection of unrelated parts that have been gathered over the years? A genuine ZN 5cc car with so many holes, splits and patches that even the Repair Shop could not have resuscitated it and another, as yet unidentified, but equally moth eaten bottom and top, neither a realistic prospect. What about the chassis drawer then, and here was an odd coincidence.

My foray into tethered cars started back in the late 60s with an M&E chassis that was missing its entire back suspension and steering and had three odd wheels. After five M&Es and fifty years, all I had left was an M&E chassis missing its rear suspension and steering, (not the same one though) but four wheels this time. Except that there were three with right hand threads and only one left hand and no tyres. Plenty of 1066 chassis parts, wheels and tyres galore but no gearboxes, motors or bodies left.

The gearbox and clutch drawer offered all sorts of intriguing possibilities if any two parts could be paired up, but no chance, and anyway, none of them matched any of the other parts I had come across. Excellent selection of magnetos if ever I find anything or anyone that needs one and a well made spur mount that does not fit any engine that I have access to, going well so far.

Last port of call was the wheel and tyre depot and a wondrous selection from the very common to the more obscure. If any Grenwyn wheels turn up then I do have the flinging tyres and this seems to be the general principle through all the drawers. The pairs of wheels that do have tyres I have nothing to put them on and the tyres that I could use I have no wheels for and similarly for the wheels with no matching tyres. The only real prospect were a number of the late Mike Day’s Wasp sized Dunlop Fort tyres and some machined aluminium hubs that had been made by his contact in China, which also did not seem to fit any available tyres.

The solid Dunlop tyres could not be fitted onto these hubs because the tyre could not be forced over the rims, but with judicious use of a hacksaw and some jig drilling, the hubs could be cut in half and then the tyres fit perfectly. Well it’s a start, occupies a few hours, and allows the mind to wander as to further possibilities, something along the Wasp lines perhaps?

Amongst the miscellaneous body parts was a well-made aluminium scuttle about Wasp size and in the aluminium store the beginnings of a sheet chassis from someone’s long forgotten project. This was all looking promising, especially as there was a Comp Special with most of an ED clutch at the back of the shelf. This had been bought for an engineless Wasp until it was realised that only a Penny Slot will fit and that the ED clutch is too large a diameter anyway. Another session at the lathe had the missing parts made, and another ‘roundtuit’ that had escaped notice completed.

The Wasp does not have a conventional gearbox just a simple series of blocks bolted to the chassis that has the one driven axle with a bevel gear and an input shaft with the pinion. The second axle and mounting block is entirely separate. Lurking in the loft was a similar device carved out of aluminium with a solid axle in ball races and an odd shallow angle bevel gear but no input shaft or pinion, kept on the off chance, and here was that chance. This is where it gets slightly unbelievable, because in a packet containing two odd gears that had been passed round at least three Club members was a shallow angle pinion with an integral, hardened, shaft that matched the bevel.

Even better, a quick eyeballing revealed that it would mesh perfectly if a housing was made to fit the hole already in the gear frame. A few hours and a 1066 ball joint later, there was a complete gearbox to fit to the chassis. Next, line up the engine and machine up a couple of spacers, drilled to accept the massive screws to match the equally massive holes drilled in the ED lugs. Could happily run a modern 10cc motor with these sized screws, heavens knows why someone had drilled a lowly 2cc diesel out to that size?

Bit like my M&E chassis, no back ends of any sort, but unlike the larger cars the Wasp has an axle mount machined from the solid, rather than a casting or manufactured item. Another couple of hours with a four-jaw chuck and lots of sparkly bits on the carpet and there was a chassis with two axles, a motor, clutch and gearbox.

Axles are recycled propshafts from long departed hydros that also used 3/16^th piano wire, as does the Wasp. On a roll now, but then the announcement that there was to be another three weeks of lockdown, can’t work slower and more time than ever available for building so press on and worry about that later. With a live front axle some cunning method of securely attaching the wheels with ¼" bore hubs was needed and equally bearings for the rear so the wheels would run on the axle, and some method of stopping them falling off.

M&E used grooves in the axles and circlips for all but the one driven wheel, and even that had a circlip to keep things uniform, although it did not do anything. In the end I annealed the ends of the axles and reduced the diameter for 4BA nuts to hold the wheels on and made brass bushes, plain for the rear and stepped at the front with grub screws on to he axle.

Chassis completed, now my favourite job, bodywork, although the most difficult bit was already to hand. This did need reducing in height a bit as it could have covered an ETA 5 and still have room to spare. A radiator cowl from brass strip and a bit of brass mesh looks the part and then a bonnet, although I did make a pattern for this as it is tapered.

Odd thing about the Wasp is that the bonnet fits inside the chassis behind the front axle, but the bit in front has to sit on the top so it has to have a subtle nudge. The rear end has proved a little more difficult as there is no possibility of any welding so it has to be formed from one piece.

Now John Goodall is an ace with a bossing mallet and a dinging hammer but anything with compound curves drives me to distraction but time is not a problem at present. Hammering sheet metal is not the most popular pursuit in the domestic situation and annealing using the old soap technique has a habit of setting off the smoke alarm that can lead to even more stern looks, so when it looked about right, then it was.

Fitting the three elements together took a bit of nadgering but the gaps are minimal compared with a Wasp. Used Oliver Monk’s brilliant suggestion of a green scourer with Solvol to give it a brushed finish and me some very black hands. Popularity was not improved when much of the black was transferred to the white sink and surround.

On a roll now with just a lot of holes to drill in the chassis to hold the body and tether brackets on and that was more or less it. In keeping with the spirit of the project, all the fixings were sourced by wading through the tubs of odds and ends, suitably whittled down to similar sizes for uniformity. Last job was the bridle, Bowden cable or piano wire but even the thinnest cable that could be gleaned from the cycle shop dustbin was 10cc size so it was a standard piano wire job with washers securing the connections.

So, in the same vein as the RVS motor cycle that never existed yet is now in a private collection and posing as genuine, here is a SBS (scrap box special) or is it a LDS (lock down special). Well, as the final design was dictated entirely by what was in the scrap box, that is what it has to be and so it will remain until circumstances change and there is a serious influx of bits, preferably that are in some way related to each other.

Not the finest piece of model making but soundly engineered and a few more parts used up that might otherwise have ended up in the bin. Now what we need is an event where we could all put out our unwanted parts and exchange them for other enthusiast's equally unwanted items, or even exchange for coin of the realm, now that's an idea. But of course, we can't.

Genesis of a ‘Track Day Special’

One of the great joys for anyone with petrol in their veins is turning up at the gates of the Nurburgring Nordschlieffe, handing over your Euros, and then being able to frighten yourself silly at a fraction of the speed more normally reached on that iconic circuit. While you are dawdling round as fast as your 1600cc of Vauxhall power will let you, there is a constant stream of bikes and cars overtaking you at thoroughly indecent speeds. Sometimes they don’t make it, which can provide a few wry moments as you pass a smoking and very second-hand Porsche that has rearranged the barriers. On the other hand you will find yourself overtaking tourist coaches, Trabants and the odd motor scooter. This is the ultimate ‘rung what you brung’ track experience.

In Britain it is a bit more sophisticated but the concept that as long as it is safe, you can run it, still holds true. Happily, the Carlton Raceway continued with this philosophy, making no concession to engine size, method of drive, direction of travel or number of wheels. There are some limits suggested, purely for safety, but otherwise there is free rein. You have two very simple choices in effect, an aircar or something else. Being lazy, and wanting something slightly different I could not be bothered building a semi scale, vintage style car with clutch gearbox etc and using a genuine old car seemed fraught with problems, so I decided on a ‘track day special’. A quick rummage through the spare engines did not come up with anything suitable, except, and here a germ of an idea formed. Many years ago, Peter extolled the virtues of the ‘manufactured’ twinshaft, as opposed to the much more expensive commercial units or unaffordable Olivers. Take rear induction engine A, plus front induction engine B, mix and match, and with a bit of jiggery-pokery, voila, a twinshaft for peanuts. This would work apparently for anything from the most basic diesel, up to 61 size glow motors. Remember the Merco 61 twinshaft in Miquel’s sale? At the time, this seemed a bit hit and miss to me, but I had read that in the 90s Ivan Prior was making replica twinshafts, using PAW internals.

This might well be the answer, bits that were freely available and replaceable if I cocked anything up, or it broke along the way, so off to Macclesfield for a conversation with Tony Eifflander. Would he be prepared to supply me with a motor and the extra parts? Well, yes, that would be possible, but why not let him add the extra housing and shaft, as they had all the jigs and screw cutting gear and could press in a longer crankpin from scratch and shim up the bearings in the new side from the word go.

This was better than I had expected and the cost for the extra work and parts very reasonable, so that was that problem out of the way. A while later, Gig Eifflander phoned to say that the engine was done, but as it was to go into a tethered car, he thought he ought to give it the benefit of his years of experience and gee it up a bit. He had even calculated the size of tyres needed for the motor to pull peak revs. All in all a true Eifflander special ‘Special’, although a second motor was built.

Sometimes life conspires, and with no immediate prospects of the track being available, the project was put to one side until our first visit to Gt Carlton. Don’t get me wrong, aircars are fun, and a more funky version was soon on the track, but I wanted something where the wheels made it go, and there lurking at the back of the shelf was the PAW. At this point the major disadvantage of using a converted aero motor manifested itself. If tyres of the correct size were used, how on earth was the motor going to be held onto a chassis, as any orientation of the motor had either the lugs, or a mounting block, perilously close to the ground. I puzzled over this for a long while until David Giles sent a photo and CAD drawing of his 3.5cc WMCR Papagai that had demonstrated some lateral design thinking. If you can’t go under the engine for any reason, go over the top ‘Simples’.

David had milled the most gorgeous backbone out of a solid billet of aluminium, with everything hanging off that. Given that we now had about a week before the next track day that amount of pondering and machining wasn’t going to happen, so a ‘muletta’ was quickly fabricated to test the theory. Somewhere along the line, for expediency probably, the top became the bottom and it was in this state that it was presented for its inaugural run. It could not be said to have been an unqualified success, in fact as a theory, it was flawed on several counts. The chassis was far too flexible.

There was not enough ground clearance, and more problematically, no easy way to start the engine. In fact there was no difficult way either, as it refused to make even so much as a tempting pop to encourage us. Pushing, starter on the tyres, starter on the shaft, not even a cough. Peter was not prepared to sacrifice his bicycle for the time honoured starting method, so it was failure on all counts. Thanks goodness then for aircars and propellers!

Coming back across the fens, breathing in the heady aroma of diesel and oil that pervaded the car, a plan B formed in my mind. Simple in concept, it involved throwing everything away except the motor and front axle and starting again, but this time doing what I had intended in the first place. A quick sketch showed the size of the lump of metal I needed to start with, which involved a great deal of hacksawing before I could start machining. This would be a true test of my newly acquired Emco mill and my resolve, as many hours of handle twiddling were needed before the backbone was complete. As I did not have a drawing as such, the fact that I could re-use the front axle mount was nothing more than luck, but that still left the problem of starting the engine? Short of taking a saw to a perfectly good bicycle, one of the crank nuts was replaced with a cone and the hope that a starter would turn it over. So there it was, far more elegant and definitely a touch of the ‘modern’ and a true ‘track day special’.

Did it work though? Well, in a word, no. Eventually we persuaded the motor into life, which led us in a roundabout way to a conclusion as to why none of our usually reliable aircars were starting or running properly either. We had purchased a new can of fuel at Old Warden, which proved to be lacking in some vital ingredient, so Peter kindly donated a bottle full of his D2000. This instantly banished all the motor problems we had been experiencing, but led us to another discovery. There is a definite knack to starting direct drive diesels on a track, and we did not have it.

I did gain a little comfort from a piece of information I gleaned that I had added a further, self-inflicted, complication, that of a silencer. Apparently, these engines with huge amounts of sub piston induction, do not function well with ring silencers, and this one certainly didn’t, so the ‘Track Day Special’ was relegated to the shelf to make way for other ‘flights of fancy’.

So there it sat for several years, taunting me with realisation that I still don’t know much about diesels until the prospect of running at Buckminster and two quirks of fate decided me to give it another go. Firstly, it had become apparent from events at Gt Carlton that the Russian Eureka engines were easy to start, very reliable and no slouches either. Secondly, a brand new Eureka arrived as an unconnected adjunct to another project. Easy, remove PAW and mount, machine up a new mount for the Eureka, screw back on, job done. Except, the PAW had the venturi on the left with the car rigged for CW running while Rytms and Eurekas have it on the right and run ACW.

Not too much of a problem, just make mirror images of everything and then wait for a set of wheels and tyres to arrive, courtesy of Pavel in Latvia. Pavel can supply a whole range of cars, spares, engines, tyres, wheels and other accessories for Eurekas, Temps and Rytms with very quick delivery, so is a very useful contact.

Wheels and tyres fitted and then one little tweak needed. The fuel nipple on the needle valve points straight down requiring a simple, right angled block to get a straight run for the fuel tube. Then I shot myself in the foot again, the bottom half of the needle valve just screws into the crankcase but also holds the venturi in place so it does not screw in flush to create a seal. I committed the cardinal sin and managed to shear it off. No problem, make a new one, except the thread is a metric superfine and whilst the lockdown presented plenty of opportunity to effect repairs, sourcing a die proved impossible at that stage.

Now, we all know what happened in March, so it was fast forward four months and a possible restart to activities in the UK so plan B, put in a conventional needle valve and make the right angled fuel feed, and ready to go. Nothing stands still and by the first event at Buckminster it was apparent that all the new twinshaft cars were sporting front suspension with spring dampers so back on the bench it went. Plenty of photos of cars with leading link suspensions so a redesign of the front end to utilise parts from a long forgotten project occupied a matter of minutes and the construction not too much longer.

The geometry did require a bit of drawing with arcs and lever arms, oh and another pair of front wheels, not for any other reason other than they had been borrowed for another ‘lockdown project’. Runs of record length are common at Gt Carlton but somewhat frowned upon at Buckminster, so a fuel cut off was essential. No way could I get one of Alex’s into the space or find anything to attach it to, so a good, old fashioned, rotary one was fabricated and fitted directly to the tank.

Now, the more observant might notice a serious omission, a total lack of bodywork of any sort. This is down to a number of philosophical and practical considerations, the chief being that I hate making bodies. Having no workshop as such, any form of alloy bashing is totally antisocial and frowned upon, GRP or anything smelly is banished outside, making it a summer pursuit only, and as for balsa, well, the dust gets everywhere. So the TDS joins four other cars that are awaiting visits to the carrosserie and an influx of enthusiasm and good weather, but then, I could get used to it in its unadorned state.

All that remains to be seen is whether the engine will start and run and whether the car stays on the track, but at least there is another ‘roundtuit’ that has been completed, and three times at that. Seems like I must keep guessing though until next season now, when the number of events planned means that more time can be devoted to some of the new projects, rather than concentrating on cars that were known to run.