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Building a Pre-Add BRM

10801 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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If I search really hard I might just have a race report in an old model maker mag ,It seems to ring a bell
QUOTE If I search really hard I might just have a race report in an old model maker mag ,It seems to ring a bell

This is the one:

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Makes the search through the loft so much easier

thanks EM
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I assume that there has been a meaning shift to the term! Most of the ex-pat english and irish I talk to in person use the term all the time with no connotation at all. Hmmm.
Course, I have teased Alan Smith of not sounding "properly british" as well.

EM talked about the 61/2 cars. It may amuse you that we race our resurrected 1/24 cars from that period every year at Vegas.
My oldest/first used a Strombecker Merc body(and the second a Lancia), but those both disappeared due to Air Force Movers mis-laying the footlocker they were in in 61! However, recently, I aquired fairly good original bodies, and I have all the pieces to resurrect New copies. I am pretty excited about this. Don is the guy who actually directed me to FINDING them.

Sorry Prof. Just having a laugh. I bet your Irish friends talk about the `auld sod' as in 'turf'. But here in Blighty an old sod is somene you should never turn your back on.
Please carry on with the slot car stories! Don't mind me. I have a prurient nature. And a large brandy.
All the time more history is revealed.

We have used a lot of Pittmans when building the new rail cars.

Best wishes,

We're rolling! the chassis that is:

The axles are cut to length (although with a 52" front track and a 51" rear track, perhaps I should say that they are cut to "shortness") In the foreground is the rough-out 0.063" brass weight plate.

The body mounts used the two centerline holes provided in the chassis. I have a "formula" body mount - thusly: pieces of 3/8" hollow plastic tube are cut well overlength to fit between the chassis and the inside of the body. Knurled brass 2-56 inserts are pressed into one end of each tube (I ease them in with a warm soldering iron - never had one pull out) They are bolted to the chassis and the body set on top. the overlength tubes are ground and filed down until the body resets at the correct height. In the end stages, I try to shape the tops of the tubes to fit the contours of the insdie of the body. When I am satisfied with the fit and convinced that the body will rest squarely on the tubes, I put a dollop of 5 minute epoxy on the top of each post, position the body and go away for a while. When the epoxy has set, I carefully undo the bolts (the post/body joint may be weak) and then reinforce that joint with gussets of 0.063" styrene sheet set in place with high viscosity gap-filling CYA

All that done - the question is now - do we have the right "look?" - The overall impression from photographs is of a very low car (35") with rear tires reaching the base of the headrest fairing and fronts that are just slightly above the body line:

The TSRF guide, forward protrusion aside, is a near perfect fit. The MRRC guide will need to be machined down to get it low enough to fit under the nose.

Paint shop time - Bowing to tradition, I have ordered some Duck Egg Blue (Humbrol) with Floquil Polly-S Sky Type S as a back-up. While waiting for the paint, and then waiting for the paint to dry, next steps include finishing the weight plate, glueing and truing the tires and fitting the wheel inserts. I have a bit of travelling to do so there will be about a one week hiatus

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It's looking good, EM!

The side view definitely matches your photo descriptions perfectly. Can't wait to see it painted and with wheel inserts. Nice project!
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QUOTE Paint shop time - Bowing to tradition, I have ordered some Duck Egg Blue (Humbrol) with Floquil Polly-S Sky Type S as a back-up.
Forget that,Humbrol #1,is almost exact match,maybe need just a couple of drops of white,but it is real close.

Trust me
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I also am in the process of constructing the BRM. I was interested to see your reference to Knurled brass 2-56 inserts Iwas wondering where you managed to buy these inserts? I canno find anything similar in my locale. Love the work so far.
I get my inserts, along with a lot of other supplies and tools, from McMaster - Carr (this is a U.S. firm)

They are certainly not the cheapest but their stock is enourmous and delivery is typically "next day"

I am sure that there are metric and BA equivalents ex-US - you just need to find a good mill supply house.

-and thanks for the compliment - it has been a pretty straightforward project so far thats to the quality of Mac's parts.

It has the right "look" to my eye. I love the overall stance of the car which is really difficult to achieve in 1/32 scale. What do you have in store for us with regards to the driver figure?

Bob S.
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Progress: Very little - and the reasons why:

The little progress - The correct shade of paint is now in hand and painting will commence as soon as I decide if I am going to further grind the front part of the body to model the trailing arm front suspension -

The reason for the lack of progress:

Didn't finish particulary well - guide kept coming out of the slot on the windward leg.

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You mean you havn't got a fixed keel on that bird, Martini? You have a fine looking crew there. Lovely stuff! I'll excuse you for now. Not quite sailing weather here in the UK yet, and I've a feeling 'Little Jim' has lost another couple of planks over the winter...
More work for idle hands.
All the best.
Ok Al, that does it! Your next family holiday is definitely going to have to be spent in Dubai! We have no less than three yacht clubs and some pretty impressive boats. I think that Beppe (Xlot) was quite impressed by my friend's 'little' boat...

And if you want something to get the adrenalin going, I can always arrange for you to have a ride in this...:-

Kind regards

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SWEEEET! Russell.
Nothing to do with BRMs, but...twin Lamborghini V12 marine powerplants! Huge rooster tails on the water! Can outrun the camera chase helicopter!
Now that IS a rich man's sport.

Thanks for posting!

Hopefully we'll se a completed BRM soon

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Well - we are moving along albeit slowly - there is this expression: "the Devil is in the details" - and so it turns out.

After looking at photos of the real car and, in view of the fact that the "ears" on the chassis offered a perfect mounting spot., I decided to add the trailing arm front suspension. the suspension bit was easy - a little cutting, filing and folding of a short piece of rectangular brass tubing - 1/8" hole on the outboard end to fit over the axle tube and a bit of solder at the inboard end to hold it to the chassis:

The tinned brass was painted with Humbrol burnishable steel and the axle tube got a coat of invisibility paint ( aka flat black)

AS in the prototype, a considerable opening in the body is needed:

And now the fun begins - first, the body seemed a bit flimsy after all that material had been removed so I elected to reinforce the upper part of the body/nose with several layers of kevlar scrim set in epoxy - glass fibre, carbon fiber, or even old nylon stocking material (the latter set in airplane dope) would do as well.

That done, I did a trial assembly at which point it became painfully obvious that the front body mount was off center by about 1mm - the plain axles sticking out each side had been less revealing. No way to fudge that much so - grind it out and make a new one - about half an hour + overnite drying time that was unplanned.

Having come this far, there was nothing to do but add the trailing links for the rear suspension - easy - a little recess in the body, two hole for two bits of wire etc. Here's the result of the third attempt to get the "little recess in the body" right:

With, of course, the requisite body filler application, setting time, sanding and repriming following the first and second attempts! Is is not perfect, but it is done!

My driver figures have never been very good, at least in part becaise they are always the last (and rushed) thing that I do so I decided that this one will be different- some scrapng to creat the "bare arm" polo shirt uniform that will go with the brown leather helmet and a lot of fiddly heating (butane cigarette lighter) and twisting of arms and hands got me to here:

With the wheel installed, he is held forward a bit and grips the rim quite convincingly - and yes, the wheel really does stick up that far!

Tomorrrow should see the first coat of color (then 24 hrs - then the secnd coat then 24 hours then the first gloss coat etc. etc) and while all that drying time is elapsing, I'll finish the weight pan.

Next post should be the finished car ( I hope)

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EM it,s looking good, like the trailing arm,s i think it may help others useing my drivers,forget the blow torch to move the arm,s, if you emerse them in hot water, reposition them then run cold water over them, that will set them in the new position. cheers macp
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