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Building a Pre-Add BRM

10849 Views 81 Replies 18 Participants Last post by  Rail Racer
The combination of an apparent high level of interest in Mac Pinches Pre-Add bdies as decribed in "News" and the recent arrival of some of Mac's new laser cut chassis has prompted me to start another project along side the W154/Patto chassis that is ongoing.

Thinking that there might be some interest in this project, I am going to document it in photos and (hopefully) brief text as it progress.

These will be a series of "real time" progress reports, not a "how to" since what I describe in one post may well be reversed in the next when I discover that it didn't work! I'll try to keep a rough log of time and cost.

The bits and pieces:

In no particular order: the body molding, driver, vac-formed screen and metal castings for the steering wheel, exhausts and filler cap (all part of the body kit) There are actually two chassis in the picture - on the lower right the laser cut chassis as supplied and spread about the middle, the parts after cutting and removal of the webs. The rear axle carriers/rear motor mount are "stuck" together. The fit of the parts is so good that the assembly is stable without soldering! Also in the picture is a guide and guide shaft bearing. One of the first things that I do with any commercial chassis is to try and figure out what guide shaft fits the hole. This is of particular interest for laser cut steel chassis because my experience is that these holes can oly be enlarged with some difficulty, the steel being very hard. In this case, the TSRF guide made for conversion of plastic chassis is a perfect fit and, on preliminary examination, to be short enough so that it will not extend beyond the front of the car (important for some rules)

Now let's do the numbers: A quick Google search yielded:

LOA: 158"
Width 56"
Height 35"
WB 98"
Wheels and tires: 5.25 X 18 front, 7.00 X 17 rear

If I believe my digital caliper, the wheelbase is spot on and the length is very close (perhaps 0.10" too short, but, the body that Mac has modeled differs from the one pictured on the site so I'm going to call it perfect!

A listing of tire dimensions for Dunlop Vintage Series tires yields:

7.00 X 17 30.2" diameter
5.50 X 18 30.1" and 5.00 X 19 29.6" so I'm calling 5.25 X 18 as 29.7"

This translates into 0.94" rear tires and , rounded to /100s, the same at the front.

Quick dimension check: The distace from the center of the rear axle carrier to the bottom of the chassis is about 0.288" If we subtract that from the radius of the proposed rear tire, 0.47", we are left with 0.18", plenty of room to add a weight pan and still meet a 0.125" ground clearance rule.

Second check - height is listed @ 35" or 1.1" in 1/32 scale. Knowing the axle height we can then check the body to see where the axle would be to give us that height in the finished car - and it turns out to be exacltly where Mac has placed the top of the rear axle slots!

Little worry (postponed until the initial chassis assembly is done and a motor fitted) - the fit between the top of the motor and the dash is the limiting factor for positioning the body on the chassis and, at first glance, it is a problem. The decision will be: can enough be ground off the bottom of the dash to accomodate the motor or will the dimensions dictate a front motor placement (and, in the latter case, isn't it nice that the chassis kit includes twoadditional motor mounts!)

An issue which has arisen long before its time: decoration: I am not really enamored of the peculiar diseased liver green that was chosen for these cars! (I recognize that there may have been budget constraints but did they really have to use paint left over from the redecoration of the railway station loos?) Any suggestions as to alternate correct liveries will be appreciated. I reserve the right to assign the car to Ecurie Martini and since this organization (long predating the red, white and blue "Martini" sponsorships) is a Belgian/American consortium, I'll paint it yellow!

Time so far, hands on and on the net, about 2 hours - parts @ current exchange, about $50

Next steps: chassis assembly, motor, axles & gears

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Looking very good EM,

I am coming to Dubai, that is my kind of boat.

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Almost there - but I thought that i would post a few shots while waiting for the driver to recover from tapping the hole for the #2 X 1/4" screw that will fasten him to the seat ( Ferrari isn't the only one that can..........)

The body is painted - 3 coats of Floquil "Sky type S" - I know that the Humbrol "Duck Egg Blue" would be more appropriate, it being a British car and all but the redoubtable Prof. Fate has assured me that they are the same color and Floquil is available locally while Humbrol is a 'net purchase with various vendors demanding from $7.50 to $10.00 " S/H" to deliver a $1.49 tin of paint! The exhaust pipes are painted with Humbrol polished steel metallizer - very nice- goes on flat but will burnish to a very convincing mettalic lustre - a few minor details to catch up with but here are the key bits ready for assembly:

The ballast plate is 0.063" brass. As I described earlier, the chassis will "float" between the ballast plate and the body thanks to shouldered nylon bushings.

A close crop is a really harsh way to look at one's handiwork:

One of the details that remains is a bit of Bare Metal Foil on the mirrors - I pulled mine out last night and - no adhesion at all - I didn't realize that the stuff expired until I read a bit in the instructions about keeping it sealed in plastic under refrigeration! The dash is covered with matte metal foil and the instruments as decals made by Virage (France) that I can find only at Slot32.

For comparison:

There are obvious differences in body shape. Based on what I have gleaned from my "Google research" the pictured prototype is the first body and Mac has modelled a later version. I don't put much stock in the color difference. The downloaded photo looks too "warm" to me. Other pictures suggest that the model color is pretty close.

Next time it will be really finished, I promise.

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That is looking seriously good! I only hope myeffort will stand muster in such closeup deteil.
I have gone a different path with the chassis. Made mine front engined. Hope it works!!
Your colour choice is great EM! I suppose if you wanted to be deadly accurate you could take your BRM and park it next to the full size one! Who is to say however, that the full size's colour is exactly the same as when it was first painted?

A cracking model!

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QUOTE I have gone a different path with the chassis. Made mine front engined. Hope it works!!

A front-engined version of the Pre-Add chassis is on my "to do" list - but I'd love to see how you implemented it - any chance of a picture?


I have yet to set up an account to embed pictures onto the forum when I get around to it i shall post pictures. Also have yet to finish this and several other projects. Don't i beg of you start holding your breath just yet.
All very nice indeed EM

That Humbrol metallizer on the exhaust is new to me. It looks great - I'll have to check it out.

I am curious about the backwards number 1 to the rear though. Is that prototypical or did you find a photographic use for that expired bare metal foil mirror after all?
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Coming along very nicely, EM!

Gotta say though... all this cool building happening lately is driving me nuts! I'm almost at the point where I'll buy ANY house just to get started on the track and get back to building again. BRM's.... P68s... T70s.... frustration!

Sorry.... just venting...

Excellent stuff!
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That is a really great looking car EM.

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Poor excuse Fergy!....Just get on with it.

That is a great looking car EM. The only thing stopping me starting on this series of cars was the rear tyres as I don't have the ability to make my own.
Talking to Mac P last Sunday he can supply the Orttman (Is that how you spell it?),tyres so there is nothing really to stop me now. They won't be a patch on yours but a gridful of these cars should provide some great racing.

I've just got hold of some trailing guides from Bruce Patterson which I think might suit these cars so I think I will order one or two from Mac. The Lancia looks pretty good to me!.


Hi Alan,

The guide hole for trailing guides needs to be drilled out to 3/16", there's just enough metal, or as suggested earier in this thread, you might want to add an alternative guide tongue. On some of the shorter wheelbase cars I had to grind away an arc at the front of the main chassis for clearance for the trailing guide.

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Thanks John. Not quiet sure about the chassis yet.

I've got a lot of PC Board still to us so I might go down that route.


Wrap -up time! Although there are still a few little bits to look to - Bare Metal Foil for the mirrors - final guide adjustment (the car has not seen the track yet) the project has moved from the workbench to the "ready for Las Vegas" staging area:

A thinner braid should bring the front down when combined with the 0.010" recess of the braid on the Las Vegas tracks but I may still substitute the MRRC guide if I get it re-done in time.

For comparison:

Adding the BRM to the other ~ 1950 GP car in the stable:

I'm hoping to at least make a sandwich of Larry LS' Talbot!

This has been an interesting exercise - the first time in 60 years that I have built a model with someone(s) "looking over my shoulder " as it were.

And now the bottom line:

I probably have about 30 hours in the whole project including perhaps 4 hours invested in pictures, processing and publishing. The biggest single time element of the project was shaping and painting the driver - took seemingly forever with at least 4 re-do's. But I learned a good deal in the process which will make the next round a lot easier.

Adding it up:

Body & Chassis: $60.00 (at current FX)
BWA wheels 13.00 ( 2 Pr)
Rear tires 6.50
Front tires 2.25
Motor 11.75
Gear set 8.00
Guide 2.50
Misc 10.00 (paint, adhesives, wire, brass plate and tube etc)
Total: $114.00

Now, is that expensive for a slot car? - not as I see it:

It works out this way - 30 hours of amusement and relaxation for $114 - that's only $ 3.80/ hour - pretty cheap - and then I get my ego massaged - many thanks for all of the lovely comments and the inspiration - so, after this bargain basement indulgence, I get a nice little slot car for free!


"The night has been long, ditto, ditto my song, and thank goodness they're both of them over" - Iolanthe
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Nothing like a bit of Gilbert and Sullivan to round off a project!

Thanks for a very informative and enjoyable thread EM. The car looks terrific
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A very nice scratchbuilt EM and I like the interesting accountancy that results in the car costing you nothing!

Great Stuff EM....Very interesting thread and a very nice model you have ended up with.

Note to Self: Must get in touch with Mac P again!.


My humble congratulations, EM. A masterpiece! That sailing holiday did you good!
I assume you'll be keeping us posted in a similar way as you work through the rest of MacP's catalogue?
QUOTE I assume you'll be keeping us posted in a similar way as you work through the rest of MacP's catalogue?

Certainly, albeit perhaps not in such detail - The underpinnings of the 4.5 Ferrari have been posted on the "Geddes Joint" thread. Currently underway - a W-125 on a Patto stainless steel chassis - schedule on that is a little uncertain as I am now in my usual "why didn't I start sooner" panic before the early May Las Vegas event with promises to prep at least 3 cars that aren't even started yet! - but , of course, I have most of Mac's newest enroute. He has warned me that the current chassis is too long to fit the later cars but we shall see.

And thanks very much for your kind comments


PS - I have had several conversations with Al Penrose ( Mr. BWA) and I have every reason to believe that tall, narrow wheels such as those needed for the older cars will be forthcoming - and that will greatly simplify things.
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super job EM, hope it go,s as well as it looks but you are putting me to shame,when i started these kits i had the grandiose idea of building 1 of each kit, as a runner with super detail ie brake drums full sus details hyraulic lines , the compleat shebang, but with the work load and lifes little lumps and bumps i think the first 1 will be finished in 2089! again great. mp
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Superb! Simply superb! I love the "floating" pan arrangement under the chassis -- now where have I seen that before?

Kind regards

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