Bugatti

23 Май 2014 | Author: | Комментарии к записи Bugatti отключены
Bugatti Electric Cars

There are times in the boatbuilder’s day when nothing more can be done on the boat, because of drying glue, or paint, or some other inevitable delay. This is not wasted time: it allows room for a second project!

Having become a grandfather in 2006, my thoughts have been turned to toys, specifically pedal cars. The plastic stuff I was encouraged to buy for a few hundred dollars might be all very well for their intended users, but they lack a certain élan. How much better would it be to make one!

There are a number of plans available for these cars, but the one I chose was the Stevenson plan for a pedal Bugatti Type 35. The Stevensons also published a book some years ago on a build-it-yourself downhill racer for 10 year olds, which revelled under the Wodehousian name of the Buffy-Porson. They now concentrate mainly on backyard boat projects, but their Bugatti is a serious attempt to capture the romance of the era, and cannot be bettered for the amateur.

Their website is http://www.stevproj.com/PedBBB.html.

What really appeals to me about this car, and all the Stevenson projects, is that they are based on the sealing wax and string philosophy: keep it simple. (In the case of the Buffy-Porson that concept is almost literally what constitutes the braking system, which may account for why it is out of print).

The original Bugatti pedal car (left) as designed by the Stevensons,

and a swank modified version (right).

In deciding to embark on any plan project from overseas, in this case the USA, one has to be aware of the limitations of available materials, especially here is Australia where choice is restricted and prices are high. There is also often a problem with metric versus Imperial measurements. This project certainly proves the point.

What follows is a description of some of the material problems I encountered, and my ways of overcoming them. It includes some complaints about inconsistencies in the plans, and explains why I ended up with such a narrow cabin in my Bugatti!

1.The first hurdle is the ‘tire’ which is specified for the rather elaborate wheels. The Schwinn bicycle company used to make 16 inch x 2.125 tyres to fit their S2 wheels, but not any longer. They had a tread on them which looked more like a car tyre than a bicycle, but the emergence of BMX bikes has just about … off the competition, so that now all you can get is the knobby type which looks quite out of place on the bitumen. Some old unused stock can occasionally be found on places like Ebay, but at high prices, and their condition cannot be guaranteed.

The design of the wheels means that the tyres run on the rims anyway, so their life expectancy must be limited. Even if you find the specified Schwinn brand you will have to replace them sometime. Some electric wheelchairs have tyres of this size, but they hardly look appropriate either.

You are probably best advised to get the least offensive bike tyre you can find, and put up with it. The kid won’t mind in the slightest.

I eventually settled on tyres for electric bicycles from Australian All Electric Vehicles, http://www.aaev.com.au They are not the square profile of the original Schwinn tyres, but they are not the full knobby array either. It is difficult enough to get 16 x 2.125 tyres anyway, so I am just glad to get some which will fit.

2.Next, remember that when an American site calls for 1 x 6 timber, it means before dressing. They actually expect you to get some 3/4 thick stock. The plans call for fir (presumably Douglas) or spruce — good luck.

But radiata pine will also work for most of the parts, with some light hardwood called for in the stress bearing components.

3.The biggest problem is in the plumbing supplies which are used to manufacture the drive train and steering components. For starters, they are of galvanised iron, which is rapidly being replaced by more modern materials. Secondly, they are in a range of sizes which just do not exist here any more.

For example, the king pins are made up of 1/2 T pieces, joined to two 1 and one 3 nipple. Our nipples have hex sections in the middle so that their threads are not damaged by tightening, but the ones referred to in the plans are like small pipes, threaded at both ends. The lengths specified are not available here as nipples.

Instead, substitute either short pipes or all threads, but in the latter case you will probably have to use brass instead of gal.

Attached to the short nipples are 1/2 female to 3/4 male bushings. We have those, but they need to be 1 long. Ours are only 3/4 long. Since they have to emerge through a piece of 3/4 timber the shorter ones will not do. There might still be a few of the older long ones to be found in places like to ancient hardware store, but the dominance of Bunnings has ensured that your choice is very limited when it comes to hardware.

Even plumbing supplies stores cannot come up with them on demand, although some of the bigger ones may be able to get them in, provided the order is big enough, which, in this case, it clearly will not be.

The bushings are tightened into position by electrical conduit lock nuts, which are unknown except in plastic now. Galvanised back nuts can be used instead, but they may have to be artificially locked down, as they have no real resistance to unwinding over time.

When it comes to the drive train, the specified 3/8 pipes and fittings might prove to be impossible to acquire. The plans does mention that 1/2 can be substituted if necessary, but that 3/8 is preferable to save weight. You might have to go with the 1/2 and console yourself that at least the kid won’t get obese pushing all that extra weight around.

Now, as a woodworker, but not a metalworker, I was lulled into a sense of foolhardy security by the reassurance that the task was within the ability of even the complete novice with a hand drill. Having almost removed my thumb on the first metalworking task, I decided that it was time to educate myself about the basics of metalworking. (The treacherous job which was almost my undoing was drilling a 1/2 hole in the T pieces.) It was only after that that I discovered that the 1/2 x 7 bolts for which the holes were intended are not readily available here either. If you want 7 (actually 180 mm.) you will only get it in M12, unless you get a cup head bolt.

Nevertheless, it pays to bone up on metal drilling, and a metal vise for the drill press is probably a very good investment.

One of the really annoying instructions is to drill out the wheel hubs to 1/2 to accept a copper tube bearing of 1/2 internal diameter. for the 1/2 bolt axles. A drill of the exact diameter of the tubing is then used to expand the hole to accept the bearing. What must be meant is that the hole is reamed to the outside diameter of the tube. But the problem here is that our tubing is sold as O.D. not I.D. so 1/2 tubing will not accept a 1/2 bolt anyway, even bearing in mind that the measurement of a bolt refers to its thread diameter, and not its shank, which is a bit narrower. (Perversely, the half inch copper tubing in question is sometimes labelled 15 mm. here instead of 12.7 mm.).

So, you will have to find some combination of axle bolts, copper tubing and reamers which will result in a good fit.

These frustrations are not peculiar to the Bugatti project. It seems that all overseas plans have some limitations on them because of our paucity of materials in Australia, and whereas our friends across the oceans can gather up their materials in a single trip to their local supplier, we have constantly to be on the lookout for the components throughout the project, which makes it difficult to plan ahead. But that is no reason to delay, so.

1. The Kingpins

Anyway, after a few days of scrounging around hardware shops and plumbing suppliers, I was able to come up with the parts for this kingpin. The axle bolt still has its head attached, which will need to be removed for the wheel to go on, and the back of the pipe which substitutes for the 3 nipple still has its thread on it. This can be removed later, or left on if it does not interfere.

The brass, which is showing through, substitutes for the 1 nipple, and the lock nuts on the bushings are standard plumbing back nuts. They might need a bit of Loctite on them to stop them working loose. But basically what we have is a unit which will fit into the space allowed between the cross members of the steering, and which should do the job.

The kingpin shown here uses brass all thread instead of the 1 nipple, and a 4 pipe instead of a 3 nipple.

All this concentration on the king pins comes out of sequence for the construction of the car as laid down in the plans, because I was keen to ensure that I could actually acquire the necessary material. But the first task specified is to make the wheels.

Some considerable care has been taken to ensure that the wheels look like the original Bugatti wheels, and spoked bicycle wheels are not catered for. The actual wheel discs are cut from 12 wide stock, but since they are over 15 in diameter they have to be made up in two sections joined together. These days it is easy enough to get hold of some laminated pine in widths of 405 mm. so they can be cut out of a single piece. Whereas the plans call for freehand sabre sawing of the outlines, you will probably save yourself a good deal of anxiety if you go to the trouble of building yourself a trammel for the saw, so that the circumferences are truly circular.

A number of different diameter discs have to be cut for these wheels, so make sure that the trammel is adjustable for radius.

I constructed a simple trammel from a piece of 6 mm. ply wood with a small diameter lag screw in one end and some double sided tape on the other. The jig saw was mounted on top of the ply with the tape on its sole, such that the distance between the screw and the close edge of the saw blade was the desired radius. Adjustments can be made by moving either the screw or the tape and saw. The saw is then placed tangentially against the stock, and the screw is driven into it at the point which will be its centre.

This can be repeated three more times after the first cut, using the uncut edges of the stock for the tangential placement each time.

The trammel for the circular cuts showing four holes for the screw (or hook) and the double sided tape. The blade travels

in the kerf between the pieces of tape.

The age old problem with sabre saws is deviation of the blade, and cutting a circle seems to be the worst possible thing to do for deviation. My saw deviates away from the work piece, but if it deviates towards a larger radius will have to be used so as not to undercut the finished diameter.

To square up the edges after the initial cut out is performed I set up a carousel arrangement on the table saw, whose blade is thick enough not to wander.

Of course, this cannot be used on inside diameters, such as are encountered on the reinforcing ply rings which are attached to the wheel discs. Here, the sabre saw can be used, as the smaller thickness of the ply is less likely to deflect the blade.

The wheel design is such that the total thickness of wood inside the tyre is only 1-1/8, which does not seem much to go inside a 2.125 tyre, but after cutting all these discs I’m not arguing!

What I might argue, however, is the suitability of these wheels in the first place. While they look all very well, I have noticed that the discs have started to warp as soon as they were cut. Perhaps some bicycle wheels would be more practical.

If the authentic look is important, laminated wheels made up of three 1/4 ply discs would be more stable. However, I am committed now, so, on to the rims discs.

These can be cut in their circumference while attached to the wheels, so as to ensure that they fit the wheels perfectly. Their attachment to an underlying solid surface also helps prevent splintering of the ply where the blade crosses the grain. In a short time, a full set of wheels and rims are ready.

The inner circumference of these rims is a more difficult proposition. To avoid splintering here, I score the cutting line on both sides with a scribe, and deepen the score until it makes a significant cut through the fibres of the outer plies. Then, I cut almost but not quite to the line with a sabre saw, and finish the job with a curved sole spokeshave, carefully creeping up to the scored line.

As long as the inner circumference of the ring is rounded beforehand, the rest can be done on the router table after the ring is glued to the wheel. Just remember to keep the brads which hold the two together out of the path of the router bit. Brads are used at approximately 3 centres to hold the ring onto the wheel, and yellow glue is alright, since this joint will be protected from water by its location inside the tyre.

The purpose of these rims is to reinforce the wheels and to thicken them where they meet the inside of the tyres. The cut out waste is used to manufacture the brake discs which attach to the inside of the wheels. These latter members act in concert with the spoke discs on the outside to hold the tyres onto the wheels. There is a discrepancy in the plans regarding the dimension of the brake discs.

They are shown to have dimensions of 12-1/2, whereas the instruction says to cut them to 12-1/4. The correct dimension is 12-1/2. The rim discs are 13 inside diameter, so there is only a 1/4 gap between the outside of the brake disc and the inside of the rim, (the two 1/4 making up the 1/2 difference in diameter).

The composite structure now looks like this:

A wheel with its reinforcing disc applied and rounded over.

When it comes time to cut the spoke discs, no actual diameter is given. Instead, a template on the plans is available. (Actually, two templates are given). However, the diameter of both of them is 12-1/4, which can’t be right, because they have to be the same as the brake discs.

The instruction with one of the templates states: After drawing outside of pattern and cutting outside of line, dia. should be close the 12-1/2. Why not make the pattern accurate and cut and draw right on the lines?

Now, the spoke disc is held out from the centre of the wheel by a 3/4 thick hub, and its outer edge is held against the tyre by a ring which is screwed through the spokes and the wheel, clamping the tyre between spoke disc and wheel. The outside diameter of the ring is 12-1/2, so the diameter of the spoke disc should be the same when in position. But because of the hub holding out its centre, this means that it should be cut greater than 12-1/2, not less.

If you work it out it should really be cut to a diameter of 12-3/4. Nevertheless, if you have already cut the spoke disc to 12-1/2, as I have, there will only be a discrepancy of less than 1/8 all round, which will be obscured by the tyre anyway, so it does not really matter.

But it is a warning about the dimensions on the plans, especially on the templates. They all need to be double checked before cutting.

The hubs which attach to the outside of the wheels and hold out the spoke discs are to be 3-1/8 in diameter, so that they can accept the fixation of the 3 flanges which support the wheel axles. I have only been able to acquire 4 flanges, so I have to increase the diameter of the hubs accordingly, and also the diameter of the central part of the spoke discs. The spokes on my car will have to be 1/2 shorter than on the Stevensons’ car.

Bugatti Electric Cars

The spoke disc is marked up and fitted against the flange.

The cuts are made with a jig saw and smoothed with a file.

Making these wheels is no gambol!!

Incidentally, the diagrams in the plans show the 3 flanges drilled for four countersunk bolts, which are 1/4 in diameter. The local flanges,as can be seen above, are drilled without countersinking, and the holes are 1/2. So the bolts which hold the hubs onto the wheels will have to be beefed up to 1/2.

They will be a tight enough fit not to require washers. However, the proximity of these large holes to the edge of the wooden hubs may make for a weakness. The rear axle on the non-drive wheel passes through a hub close to its edge, and the recommendation there is to reinforce it with a hose clamp.

I think that would be a good precaution here too. To the right you can see the screw fastener of the hose clamp on the hub.

Once the parts are all cut and fitted, the construction of the wheel proceeds along these lines:

1. Centre the brake disc over the wheel and screw it on temporarily around a line 1 in from its outer circumference.

2. Centre the spacer hub over the other side of the wheel, and screw and glue it to the wheel.

4. Mark all the parts so that they can be located again over the screw holes, and disassemble them again.


5. Fit the tyre over the wheel, by cutting relieving notches on one side of it if necessary. And it is necessary. I got by with three cuts and a hell of a lot of leverage.

You need a hacksaw to get through the wire cable in the inner beading of the tyre, and something to use as a tyre lever. The flat spanner I use to put the blades on my table saw was just right for the job. Some candle wax rubbed onto the rim of the wheel helped slide the tyre rim over the wood too. The cuts are made on the inside surface of the tyre, but they do not have to be deep enough to show around the brake disc.

I suppose that is just in case. The inside (and, therefore, unseen) surface of the tyre is easily determined in the case of my tyres, which have Chinese characters on them on one side. Hardly what one would expect of a Bugatti!!

6. Reassemble the parts, centre the tyre and screw down again, gripping the tyre permanently between the brake disc and wheel on the inside, and between the spoke disc and wheel on the other. The plans say to cut relieving kerfs on to underside of the spoke disc to allow it to take the bend, but I found this unnecessary. Gentle and slow clamping was all that was necessary. An occasional superficial surface crack opened up on the outside where the tension was greatest, but they were not a problem.

The spoke disc was painted with epoxy resin before getting its final colour, and that soaked into the cracks and bound them down.

Nevertheless, as the final trimming of the spoke disc was done on a router table, it would be easy enough to continue the circumferential cuts on a small router bit to achieve the kerfs which are called for.

The spoke disc is gently, and then firmly, pushed into position, overcorrecting here because the tyre is not yet on.

It would probably be a good idea to paint the parts before their final assembly, to avoid smudges on the tyre, etc. but after the struggle to get this one tyre on there is no way I am going to take it off again. Perhaps for the other three wheels!

A coat of silver on the spoke disc and ring blends in nicely with the galvanised hex head sheet metal screws, and the antique ivory recommended for the wheel disc

in the plan works well too.

The advantage of making the wheel components the way I have, on a carousel arrangement through a central spindle, means that I can be certain that the hole is exactly in the middle, so all I have to do now is enlarge it to fit the axle and bearing. The wheel is placed on a drill press, and the small diameter drill which has been used up to now is run down into the hole to centre the wheel under the drill. The wheel is clamped into position and the drill bit is changed for a larger one, up to the 1/2 necessary.

With the copper tube bearing inserted through the enlarged hole, and the outer flange snugged down over it, holes for the flange bolts can now be drilled through, and the inner flange can be connected to the bolts and tightened into position.

The hubs for these wheels consist of the aforementioned flanges, into which are screwed 1/2 male to 1/4 female bushings. The bushings have to be drilled out to accept the 1/2 outside diameter copper tube, into which the axle rods are inserted. 1/2 to 1/4 bushings are not available here. The nearest I could come up with was a 1/2 male to 1/2 capillary union in brass.

Apart from the dissimilar metals causing some problems with corrosion, which can be overcome, these seem to be even more useful than the bushings, since they have only a small internal lip to be drilled out to 1/2 in order to have a 1/2 channel all the way through.

The flange, the union and the constructed hub.

When the inner and outer hubs are finally bolted together through the wheel, the centre of the brake disc is pulled into contact with the wheel. At its periphery it is held away from the wheel by the tyre. So, it takes on a concave contour.

This may seem wrong, but it is the only way of doing it with this construction method. By careful alignment, the through bolts and the central hub unions (or bushings) should all line up perfectly, and a 1/2 diameter copper tube is inserted through from the outside union to the inside one, and is trimmed off so that it is just a little longer than the distance from one union end to the other. In this way, washers which are later fitted over the axles, ride against the copper tube, and not against the hubs. The quality of the axle mechanism depends heavily on the snugness of fit between the inside of the copper tube and the shank of the bolt which acts as the axle. Unfortunately, at the moment the inside diameter of the copper tube is 10.8 mm. and the diameter of the shank of the axle bolt is 11.2 mm. so some adjusting is going to have to happen before the wheels can be fitted to the car.

The copper tube bearing is only 0.9 mm. thick, so reaming it is not a practical proposition. Instead, the axle bolt will have to be machined down to fit. That means that its zinc coating will be lost and it will rust, so the best option will be to replace the bolts with stainless steel.

304 stainless is not too expensive.

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