[Felix]

I was walking along the front lot earlier looking for sections that still needed raking, when I heard the rumble of an antique motorcycle engine coming around the corner. I turned around and found that it was a tiny bright red Austin Healey Sprite. I remembered that I probably have one of those packed away somewhere in the basement, possibly even in the right scale. I eventually took a look and found a Healey 3000, as well as a 32’nd scale Sprite. It was a nice AirFix box of the 1958-1961 Sprite MkI. (1997 re-box of 1961 tooling).  However, the contents weren’t so nice and I recalled that I had set it aside deciding that it wasn’t worth spending time on it. But seeing the real thing drive by, gave me renewed motivation.

Fig. 1:   You can’t judge a book by its cover – you can’t judge a kit by its box-art !

I had built many model cars when I was a kid, but never a 1/32 scale, and this one looks like the tiniest of the tiny. (I use two large magnifying glasses while doing intricate work, but here I could make use of a microscope!)   I started work on it and found that the tooling, moulding, casting were even worse than I had initially thought. The front fender pontoons were lumpy. The three sections making up the front end of the car did not fit properly. The hood seam in front of the windshield was scored different thicknesses from one segment to the next. Door seams were irregular. Rocker panel seams were different heights and shapes between left to right side. Other body features that were supposed to be the same, were different sizes and shapes from each-other, and not symmetrically positioned on the left and right sides. The headlight lenses are nice but the dome sockets they are to fit into on top of the hood are not smooth and semi-circular but are instead elongated leaving excess at the top and a gap at the bottom. There are other inconsistencies that I won’t bother listing, plus more I’m sure to discover. (Once again, it seems that I’ve stumbled into an overly difficult model to work with.)  But I decided to stick with it anyway.  One of the problems for me in this smaller scale, has been motivation, so I decided now that I have a bit, I should make use of it.

 

Fig. 2:   Sprite in another of the many standard colours, ‘Mint Green’.

 

I assembled the front end body sections, and started the prep by sanding down those seams and all the lumps on the curved surfaces. I’ve never used body putty on a motorized car, fearing that it may crack under flex during competition, but here I couldn’t avoid it and decided to take the chance. I filled in the top hood seam and the small body-fit gaps in the front, as a start.

Fig. 3:   Kit contents.

 

There is something else about the body that doesn’t seem quite right. I almost bought a 3000 Mk III when I was a youngster, but I don’t know much about the Sprite, so I started searching the references to learn a bit about the car. If I’m going to the trouble of building it, I want to do it right. I couldn’t find matching wheels in my collection, so I tried the body onto a ‘Carrera Go’ chassis, and even at that 1/43 scale, the chassis was too large for this tiny body ( ~10.5 cm x 4 cm; ~4” x 1 ½” ) .

With the kit wheels in place, the body looked very high off the tech block. I thought the problem may be that the wheels were out of scale too large. Doing a search and some arithmetic, I found that the kit tires are properly scaled and do correspond to the vintage Sprite tires, “Cross-ply 5.20-13 tyres”, which are apparently 23.1” or 587mm overall diameter (on nominal 13” rims). The kit wheels have a Rim diam = 11mm,  Tire diam = 18mm,  giving a Track clearance = 7mm with tires touching the inside of the fenders, and that already appears far too high for the tiny sportscar. Adding a 2 mm tire/fender clearance on the model, (which would be more realistic and would be needed to allow for minimum body roll), gives 9 mm track clearance, and would convert to 288mm, or 11.3” road clearance on the real car. (That 2mm tire/fender scale clearance converts to only  2 ½ ” tire/inside fender clearance available to the real car, still far too small.)

 

I don’t own a sports car, but the road clearance from the bottom of the rocker panel of my mini-van is only 8 ½” ; the other cars in the garage are lower.  Since the wheels are to correct scale, the only conclusion I can draw from this analysis is that the model is out of scale too shallow. As a result, they had to cut the wheel arches too close to the top of the body. The shallow body also gives very little clearance for the tires inside the fenders thus the whole body is raised far too high off the track. All of this is even apparent from photos of the real car. (Exterior photos, as well as photos under the bonnet show that there is plenty of space, and structure, between the top of the tire and top of the fender.)

 

Fig’s.  4 & 5:   Body proportions of the kit and the real car.

It’s very obvious from comparison of these two photos, that the model body is out of scale too shallow, streamlined. (Compare the heights of the door panels, the heights of the fenders above the cut-outs, and the space from top of tire to top of fender.) Unfortunately, it’s an effect that can’t be corrected on this model without major surgery. On the other hand, using smaller wheels helps with the body height and track clearance, but makes the wheel cut-outs on the model look even larger .  (I may have to do what I see done on my Ninco XK120 and many other sportscar models – build a step drop between the body and chassis. Even on the real car, some chassis components show below the bottom edge of the body. However, such a step will limit my chassis design and it’s dynamics.)

 

This thing has given me so much trouble; Looks like my initial assessment was correct and I should have just left it in the box! In any case, now it’s become a challenge!

So I have been searching for correctly scaled rims and tires. I have worked out four possible chassis designs to fit this tiny body, but until I have the wheels in hand I can’t finalize the adjustments on the body or the detailed dimensions of the chassis. I’m looking for rims 13” nominal which usually work out of be 13mm diameter at the centre ridge and 11.5 mm diameter at the outside edge, depending on the manufacturer. I need 5mm wide for the front pair and 7mm for the rear. Corresponding tires would be 18mm diam before truing.  It’s going to be difficult to compensate for the shallow body; I may have to do other adjustments, but I want to get the best balance possible.

 

I am always doing what I cannot do yet, in order to learn how to do it.   Vincent Van Gogh  

 

Topic

[Felix]

 

I’ve now found in my parts collection a set of rims and tires correctly sized for the front wheels; seem to fit well. Now I need rear wheels: a nominal 13” Alu rim, with 11.5mm diameter at edge, 7mm wide, plus corresponding tires. So, I am on the search!

 

Fig. 6:   Sprite body shell viewed through magnifying glass; sanding dust from first stage still on the body.  (More body work yet to be done, possible further adjustments, but have to first find the correct rear wheels .)

 

Felix.

PS:  The Sprite has a Bonnet; since it doesn’t have a trunk, does it still have a Boot?!   

 

[Ken]

Hi Felix,

That’s a wonderful start to a very cool car.

Jim O made a Sprite.

Jim M also has one that he got from Chris Walker.

They are both on the database, and have a completely different stance. It’s always up to the builder in the end.

A word of caution. Very narrow cars don’t like wide tires on the rear, or they just roll over in the corners. Equal F/R might be a better choice. The Sprite is very narrow.

I look forward to seeing it completed. I have the same kit on the back shelf somewhere.

Ken

[DB]

Hi Felix  very cool car. I have models of an Anglia, Escort, A35 and Triumph Herald. I used Pendle wheels.  See my pic of the Anglia. Front wheels .. 11.47mm x 5 … Rear 14mm x 7.43mm.  The rear takes a larger Dart tire.  I have a spare of Pendle wheels 11.47mm x 5mm if you want them for free.  Pm me with your address and I will drop them I  the snail mail.

 

Dave

[DB]

I also found a set of 14 x 7.5mm wheels which are the Anglia rears.  You can have those if you want.  Let me know sometime.  Dave

[Felix]

Thank you Ken, Dave, for your useful advice and encouragement.

Yes, it is an interesting little car. I just wish they had done a proper job on the model; a lot of flaws to work with, some impossible to correct.

You’re right Ken, I don’t want to use wide tires on the rear. I ordered a set of wheels from Pendle that I though might work from their description, but when I tried them in place they were too wide. I would like to try 7mm on the rear as the upper limit on width; if that fails I may have to go with the 5mm as on the front.

Thank you for your very generous offer, Dave, as well as for taking the time to take photos.  I do already have the 11.5mm diam x 5.1 W rims, with corresponding tires. I got them from Pendle, for use on the front.  I also have their nominal 14” rims in a 6mm width, with tires, but the diameter ends up being too much for this tiny body. As a last resort, I may have to end up going with the 14″ ones, but I would prefer to stay true to the scale of the original car. Also, at that rim size, truing the tires down to fit this body leaves them out of scale very low profile. That would probably work better if I were doing a modified race version.

A lot of problems created by this squashed body!  Surely if 14” rims are available in 6 and 7mm widths, the 13” ones should be available in those widths, somewhere !?

Thanks again guys; Greatly appreciated.        Felix.

[DB]

RS Slots has  13 x7 mm wheel.

[Ken]

Art just sold 6-pair of 13″ wheels.

2-pair of 5mm. 2-pair of 7mm. And 2-pair of the very rare 9mm. All were premium BWA’s.

BWA used a better quality aluminum, or a better tool/cutter, or both. They have a super shiny finish.

I was fortunate to already acquire several sets from Art over time, or I would have jumped on those rare wheels.

There are a few 3L GP cars that still need to be built. It’s hard to build one without a pair of 13×7’s and 13×9’s.

[Felix]

Thanks Dave, Ken, for the extra info.  I will try the RS Slots, order a few of their rim sizes and keep them as back-up.   Actually, I’m the fellow that bought those BWA ‘unobtanium’ rims from Art, plus six sets of corresponding tires. The medium rims are 7.6mm wide and the tires go to 8.8mm wide; I knew they would be too large for this tiny body. The small rims are 5.1mm wide and tire options go to 7.2mm, so those may work, but as you advised earlier, they look a bit wide once placed inside this body. (May be better to save the BWA’s for another build, where I need to match front and rear rims.)   The 5mm ones I have from Pendle have flat sidewalls on the tires, barely the width of the rim, but will do for the front.  In the end, it looks like it’s best to go with those same 5mm rims on the rear and look for a D’Art rear tire with a bit of a bulge to give about a 6mm overall width.   Thanks again for the good advice.

[Ken]

Felix,

You did well in buying those wheels. They are identical in size to what RS Slots makes in the UK.

Colin Sparks from RS Slots took over where BWA left off.

The main difference is the shine of the aluminum. They spec out to the exact same dimensions.

The only wheel RS Slots didn’t copy are the 13×9’s. Not enough call for that size.

Ken

[Felix]

Part B:   I’ve returned to work on the Sprite. I was hoping that I would be on to starting the chassis by now.  Unfortunately I have found more defects in the tooling that cannot be ignored. I had noticed from the start that the shape of the front wheel cut-outs is wrong, but hadn’t decided whether to correct it.  Comparing photos 4 and 5 in my first post, above, shows that the front wheel cut-outs are elongated rather than circular. The following two photos, below, also illustrate the same. (The box art for the kit does show the correct circular shape.)  It’s a small detail but, elongated wheel well cut-outs just don’t suit a classic sports car.

 

Unfortunately, I have found more errors in the tooling of the domed headlight sockets/pods. I had already mentioned at the start that “The headlight lenses are nice but the dome sockets they are to fit into on top of the hood are not smooth and semi-circular but are instead elongated leaving excess at the top and a gap at the bottom.”.  (This refers to the elongated shape of the front face of the sockets that the headlight lenses are to fit into –  evident in the 6’th photo of the first post, ‘sanded body shell viewed through magnifier’.)

I now find three more flaws, making a total of four distinct errors in the headlight domes.  On the real car, the headlight pods on top of the bonnet have a very pronounced curved shape; the origin of the name “Frog Eye”. The profile of the tops of the pods ends horizontally as it reaches the front. The front face of the sockets is vertical so that the headlights aim horizontal. These three features show up clearly in the photo below, as well as in the earlier photo of the Mint Green sample.

 

Fig. 7:   Circular wheel arches; profiles of headlight domes.

Note the circular shape of the wheel well cut-outs; the pronounced curvature of the headlight domes, top surface ending horizontally at the front, front facing edge is vertical.

 

On this model there is almost no curvature on the tops of the headlight domes in side view.  [The model tooling appears to employ almost straight tubes embedded onto the top surface of the bonnet.]   The profile of the top surface of the pods at the front, end at a slightly upward angle above the horizontal. When viewed from above, the seams between the domes and the bonnet surface look good and are curved, but this is only by virtue of the intersection of any cylinder partially embedded at an angle into a curved or even planar surface.

The fourth flaw in the tooling of the headlight pods is that the leading edges are cut backward at an angle, so that the faces of the headlights point at an upward angle to illuminate the tree-tops! (Much more visible with the model in hand than in a photo.)  This also results, (when viewed directly from above), in a small open gap between the back bottom edge of the headlight socket and the front top edge. This may have been done to make the casting step easier.    [ However, I have the Gunze 24’th scale model of the Triumph TR2 Le Mans ’55, with the same type of headlight pods;  that kit has none of the four tooling flaws on the headlight assemblies of this one – the front openings in the sockets that hold the round headlights are themselves round, not elongated; the headlight pods have a very pronounced curve; their top surface ends horizontally at the front; and the front facing edge of the socket is vertical – all as it is on the real cars, both the Sprite and TR2. ]

 

Fig. 8:   Elongated wheel arches on the kit body;  profiles of headlight domes.

Note the elongated front wheels well cut-outs; the almost straight profile of the headlight domes, ending at a slight upward angle at the top front, and the front facing edge cut back at an angle (not as visible here; slightly visible in photo-3, of first post).

 

I knew there were problems with the tooling of this kit but didn’t count on there being this many. Now that I’ve started, I need to finish it properly. I know I am going overboard with this tiny model, but I consider it an exercise, an opportunity to apply a few of my ideas and techniques.  I will try to make some adjustments to correct the elongated front wheel cut-outs and the four flaws in the headlight pods and sockets.  These may seem to be trivial considerations, but it’s the fine details that define the charm of this little ‘frog-eye’ body.

 

I must from time to time ask, how did I let myself blunder into this agonizing absurdity?

 

[Felix]

Part C:   More work done on correcting the wheel-well cut-outs:

Fig. 9:   Another view of the elongated wheel cut-outs, the kit wheel as reference.  Also, the front edge of headlight pods.

Compare the profile of this wheel cut-out with that of the photo of the front fender of the “Irish Blue” car in my June 7 post (Fig. 7).  A very obvious difference in the shape of the cut-out compared to the real car.

[By the way, in this kit the Right front wheel cut-out has a different profile, and is more elongated (at the top) than the Left one; another error in the original tooling. The right-side white insert plate does not fit anywhere close, into the left-side cut-out.]

Note here again, the backward tilt of the face of the lens socket on the headlight pods.  (The body is horizontal; bottom edge of rocker panel is parallel to the bottom edge of photo, can be verified by cropping. )

 

 

Fig. 10:   Black backing sheet cemented in place; Adjustment plates placed loose inside wheel-wells.

A black 0.5mm flexible polystyrene sheet used as a backing plate has been cemented to the inside surface of side panels. This is needed for support, strength, and 3-D alignment of the adjustment plates to be cemented inside the cut-outs.  Centres of the white insert plates are press cut. Blue outline is to guide the initial cut; Red line is a guide to the final cut.  This is a loose placement to check fit and alignment; they will be tighter after final cementing.  (This indicates that a sub-layer of black 0.5mm backing sheets, cut to shape, should be added under the white plates to raise them.)

 

 

Fig. 11:   Sub-layer pieces and white plates chemically welded into place.

A sub-layer of black 0.5mm backing pieces, shaped to the same profile, were added before the white plates, to account for surface contours of the fender areas.  The white adjustment plates were cemented on top of the backing pieces; guide markings dissolved away, but can be re-marked. (Ink migrated to the seams but does not represent gaps.)

 

 

Fig. 12:   White adjustment plates sanded down.

All components had fully fused and cured. White layer is sanded down to a smooth junction with the original body surface.  As most probably already know, the worse thing one can do during this step is to sand using a regular sheet of sandpaper in hand. That would guarantee cutting into one of the materials on one side of the junction, deeper than on the other.  I used several shapes and sizes of sanding blocks with various grades of sandpaper fused to them, in order to ensure that only the white insert plates are cut down, and only until they reach a smooth junction to the surrounding original surface.

(The seams do not appear to have any space for putty fill, but I will try to press some in. The next step in the work.   . . . . . )

Hope this may be of some help and interest to some members.      Felix.

 

[Felix]

Part D:   Work completed on correcting the wheel-well cut-outs:   (I haven’t had much time to devote to the hobby recently but managed to get this stage of the work finished.)

 

Fig. 13:   White adjustment plates re-marked for grinding out.

As expected, I found that there wasn’t room in the seams to hold any body putty; there are a couple of spots at the bottom corners of the adjustment plates. The surface colours are deceptive, grey-white-black-beige areas. The seams and surfaces are in fact, all completely smooth.  Here I have re-marked the cut-out boundaries, ready for drilling and grinding out.

 

Fig. 14:   New correct wheel cut-outs are drilled and ground.

Starting with a small drill bit at centre, moving up through various stone bits, I ground out the openings. This final stone was used to bring the wheel openings to 18 mm diameter.

I discovered long ago, that in order to enlarge a hole in most materials, it’s best to use a conical grinding stone. It allows uniform contact and cut along the whole circumference, increasing the size of the hole, while keeping it centred and keeping it circular.  On the other hand, a cylindrical stone or a sanding drum only contacts at one point and relies on moving that one contact point uniformly around the inside of the circle.

 

Fig. 15:   Some of the excess black backing plate is ground away.

Excess backing sheet at front and rear has been ground off, and bottom in between the wheels has been cut down a few millimeters. It will be sanded down further after final adjustments are done on the bottoms of the cut-outs during chassis fit tests.

 

Fig. 16:   Right side view.

From Fig 16, it looks to me that the front right wheel opening is cut back too far; the space between the front edge of the cut-out and front edge of the car looks much larger than on the left side, shown by Fig 15.  After all this work, that looks like a major grinding error on my part. Is it possible that the grinding tool migrated during the cut?

That frustrated me to some significant degree! So I set out to do some tricky measurements on those curved forms. I set the body on its side on the operating table, and held a long plate up against the bottom edge. I placed a block up against the plate and in contact with the leading edge of the body.   That allowed me to use a caliper to accurately measure three perpendicular distances from:  (a) the front edge of the body to the front edge of the wheel cut-out;  (b) the front edge of the body to the wheel centre;  and (c) the front edge of the body to the back edge of the wheel cut-out.  As a more general back-up, I re-measured using a small steel ruler.

Value (a) measured at 6.0 mm.  Value (b) measured at 15.0 mm.  Value (c) measured at 24.5 mm.

When I went to the left side, the measured values came out the same, when rounded to one decimal precision, to my surprise and great relief.  The key result is that the distance from the front edge of the body to the front edge of the wheel cut-out is now the same on both the left and right side of the body; 6.0 mm, to two significant digit accuracy and one decimal digit precision.  These measurements also verify that the front wheel cut-outs are now correctly centred at the same distance from the front edge of the body.

(Recall also, that the wheel openings were ground out to an 18 mm diameter. The above measurements also agree with that, in that 6.0 to 15.0 is 9.0 mm, and 15.0 to 24.5 is 9.5 mm, each value representing the approximate radius of the cut-outs.)

 

I discovered early on with this model kit, that besides the elongation of the front cut-outs contrary to the shape on the real car, the original cut-outs on the model have slightly different shapes, sizes, and positions, between left and right sides. As indicated in the photos of my previous post as well as this one, the front-right wheel opening was different from the left, and needed the largest adjustment to shape and position.

Next stage of work is the correction of the headlight sockets; adjusting them to a round shape and adjusting the aim to the horizontal.

 

[Arthur]

Thanks for posting your observations and efforts (along with photos) Felix… the problem with many 1:32 bodies is that they are not symmetrical and it is only after you mount a chassis that it becomes really noticeable unless you take care to check and double check as you did… great work! Looking forward to the headlight adjustments…

The Happy Canadian Scale Modeler!

[Felix]

Thanks Art, for your considerate words of encouragement.  I got to the hobby shop and picked up some raw materials to work on the light-pod corrections, and on the chassis.  I think I have a solution for the headlight adjustments, and by hook or by crook, I will make it work!

[Felix]

Part E:   Continuing work on the Sprite body; First step in correcting the headlight aim.

(Rather than random half hour intervals, this detailed work requires larger blocks of free time.  For the reasons I’ve shared with members privately, I have had considerable difficulty finding that time to devote to the hobby. Sorry for the slow progress on this work.)

 

I’ve moved on to work on correcting the tooling errors related to the headlight pods on this model. For easier reference, I will list here, the main defects I had earlier described related to the headlight pods.    ( For the full discussion, see post #18635, June 7, 2021, paragraphs – 2, 3, 5 ;  four distinct errors in the tooling of the headlight domes on this Airfix model, referring to Fig’s 6 [from post #18598, May 21], and 7, 8 [from post #18635, June 7, 2021]. )

On the real car:  the front face of the headlight sockets are round, to fit the round headlights, (rather than elongated as illustrated in Fig 6 of the Airfix model);   The headlight pods on top of the bonnet have a very pronounced curved shape;   The profile of the top surface of the pods ends horizontally as it reaches the front;   The front face of the sockets is vertical so that the headlight aim is horizontal.   (These last three features are illustrated clearly in previous Fig. 7 and 8; comparison between the real car and the Airfix model.)

At this step in the work, I am trying to correct the headlight aim back to the horizontal. There are two methods that can be attempted to achieve this. One is to cut into the face of the lens sockets of the headlight pods to make the leading edges vertical. However, as previously described, there is already a gap in the body shell between the top and bottom of the lens sockets when viewed directly from above, and this method would create an even larger hole at the bottom of each socket. The second method is to extend the lens sockets forward by adding small angled sections to make those leading edges vertical. This method will also have the advantage of allowing for the correction of the profile of the tops of the pods, that is, allowing for the formation of a curve on the top surface, re-shaping it to end horizontally when it reaches the front.

 

I started by carefully aligning the body shell to the grid and clamping it into place :

Fig. 17:  Body shell accurately aligned to the grid and clamped in place.

 

I have  ¼” diameter polystyrene tube which I cut off square in a mini mitre box. It fits well in the cupped form on the bonnet, pushed flush up against the face of the headlight socket.  (I checked that the tube was straight – it rolled freely on polished granite slab.)

Fig. 18:  Polystyrene tube pushed flush up against the face of the headlight socket shows the true angle of inclination of the headlight aim.

Here we have the first clear illustration of the headlight aim. The error in the aim is very obvious. It’s a significant deviation from the horizontal. ( Again, the headlights would do a good job of illuminating the tree-tops along the English countryside! )  In order to do an accurate correction, we need to measure this angle of elevation.

Some basic trigonometry and application of the inverse-tangent function on the rise of 1 grid unit over the run of 9.5 grid units (see red reference dots in photo), calculates the angle of inclination at 6.0090° .

 

Well, any proper measurement deserves another! As a backup, I decided to do a direct measurement using an extra large drafting protractor.

Fig. 19:  Protractor measurement shows a 6.5° angle of inclination.

Direct measurement of the angle using an extra-large protractor gave a clear 6.5° angle of inclination of the headlight aim.   (All of these measurements involve visual judgement: where the edge of the tube crosses the grid line, for the trigonometric calculation method;  where the edge of the tube crosses the protractor line, for the direct measurement method. However, a careful protractor measurement requires viewing the intersection of the tube edge and protractor scale immediately above each separate  intersection point, which can not be done with the single view of the camera. That careful measurement read a clear 6.5° for the angle of inclination of the headlight aim.)

 

What can we conclude from this exercise?  Is the angle of inclination of the headlight aim on this kit 6.0° to 6.5° above the horizontal?  Quite convincingly so, but possibly not convincing enough for all?  What we can certainly conclude is that, in the tooling of this kit, the headlight aim is far too high above the horizontal and needs to be corrected.  Also, our best estimated measure of the required correction is about 6.25 degrees.

 

This has turned out to be an exercise in perseverance !   Until next step; Different time, same channel !        Felix

 

 

[Arthur]

Excellent report so far Felix!!!

The Happy Canadian Scale Modeler!

[f1nutz]

Incredible attention to detail Felix!

[Ken]

The concours restoration is coming along nicely. This looks to be an incredibly accurate build so far. Nice work Felix. 🙂

[Luis Meza]

Wow Felix, your level of dedication and attention to detail are to be admire, it is very encouraging into doing things with care to raise the bar on scratch build

[Felix]

Thank you, gentlemen. I am humbled by your words of encouragement. (I must say, it was never my intention to do so much work on this body shell.)  Sorry that I can’t devote the time needed to move the project along at a more respectable pace.

[Author]

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