[Arthur]

What better time to get into a Lotus 30 build than now – just in time for the upcoming CANAM Thunder!

After some contemplation and a little scavenging then more contemplation it was settled. For this build I would mate the new DArt Lotus 30 body kit with full interior and fantasy livery to a scratch built chassis. I planned to use the following major components:

• DArt Lotus 30 Body Kit;
• ‘low power’ BWNC1 in a sidewinder configuration;
• Slot.It spur gear with scavenged 15T nylon pinion from some electronic device I threw away many years ago;
• 2 pair of BWA small 13″ (11.85mm diameter) wheels all with DArt DA0211 urethane tires & DArt small inserts (customized);
• oil lite Parma bushings in the back, 1/8″ brass tubes for the front stubs; and
• scavenged ‘push in’ guide from a Fly or other RTR scrap chassis.

The trouble with making a ‘low power’ sidewinder model is always the gearing – so when I found the 15T nylon pinion with the correct pitch I couldn’t resist. This sidewinder chassis would also be a torsion version using 3/32 piano wire as the spine sleeved by a section of 1/8″ brass tube. The defining feature up front for this chassis would be the independent pins allowing the front wheels to have noticeable negative camber. I’ve wanted to experiment with a front end like this for a long time… if it didn’t work then it would be easy enough to replace the sleeves with a straight section of tube.

Several extra bits from the body kit are set aside for parts storage – like the larger inserts, clear lenses, short stacks & valve covers – they’ll come in handy on another project sometime down the road I’m sure. I plan to use everything else.

The Happy Canadian Scale Modeler!

Topic

[racer68]

Art

The plans for your chassis sound interesting. I’ve played around with stubs and negative camber but my building skills are not yet up to the promise of the concept. I hope you’ll share the details of your chassis build to give us newbies a chance to see how it’s done. I think it’s great that you can scavenge and repurpose pieces for your builds. You wouldn’t remember the electronic device that you took the pinion out of? I’m sorting through some electronic trash, dead DVD players, old hard drives and the like trying to figure if it’s worth my time to disassemble them to scavenge parts and materials for slot car racing or scale modelling.

Cheers

Steve

 

[MiA]

Looking forward to seeing this one progress!! B-)

[Arthur]

Continuing along…

One preliminary recommendation – if you need to rush this or any build then you shouldn’t start it. Race deadlines are great incentives but there’s no prize money – so take your time, measure twice & cut once, eyeball, clean, test fit and double check everything before gluing or soldering. I wouldn’t start this project less than 5 days away from a deadline unless you are prepared to pull an all nighter or two.

Wheels & Tires

After gathering all of the remaining bits & pieces I’ll need for the build my first step is ALWAYS to mount the tires to the wheels. I chose the smallest and narrowest 13″ BWA wheels and selected four DA2011 tires which look great with them. To help seat the tire for best fit I removed material from the inside of both wheel flanges using my Hudy and a Dremel cutting disc. After gluing the tires on I set them aside overnight to dry before truing.

[You can proceed to The Body (below) while the glue dries…]

I trued all four tires to the same diameter – a hair over 20.5mm – and then placed them inside the wheel wells to see if they looked proper. In some cases it may be helpful to use a couple of axles and mount the wheels then drop the body on top to get a feel for what you are up against. Again, don’t rush this step, especially since this body has deep and narrow wheel wells… Given that this is a low power motor build the overall diameter of the tire is important since ratios are limited. Satisfied with the diameters I finished each tire (profiling it) on the Hudy and set all four wheels aside.

The Body

I cleaned up the lightweight body, opened the front vents, and cut the fore and aft body post locating stumps then ground them down. Since the plastic is very easy to work with a dremel cutting disc applied at low speed (use the side of the disc to grind the rest away) cleans away the unneeded stubs nicely. Be careful if you are using side cutters to cut the body post locating stumps – they will pull the stump as they cut into the post and possibly deform or tear the plastic base. If the locating stumps don’t interfere with your chassis then you can just leave them be.

I would use two brass side plates to help mount the body – so the kit’s #226 styrene tubing was sliced into 4 pieces and the base of each piece was cut at an angle for maximum contact with the body and to ensure the post would remain perpendicular relative to the chassis. If it remains in the position you want without glue then it will with glue. Again, no surprises next morning. For the front two posts I used an X-acto knife to cut away a small section from the edge of both front tubes to lower them beyond the bottom edge of the dashboard. If you have one of these kits you will know what I mean…

I used the Clear Gorrilla Glue (see workbench essentials thread) which I applied to each stump to secure all four posts. This should be quite strong and is lighter than epoxy – but if you are in a hurry and can’t wait overnight for it to dry then use a quick cure epoxy instead. As I slid each tube down over the stump there was enough glue on the post to leave a filet around the base of the post/body which is what I wanted. After positioning each tube (by eye) straight up (since everything is upside down) I left it alone (again, flat and upside down using some silicone spacers) overnight to dry.

After the posts were dry I cut .024″ brass plate strips for each side. I planned to solder a hinge to each of these plates once the rolling chassis was complete. The hinge would allow some body float and since I wasn’t too concerned about lowering the body’s CoG (by using heavier side plates) these lightweight plates could be snug up under the seats to give flexibility with the chassis design.I used the side of the cutting disc to trim the tops of each body post so that they were flush with the bottom of the seats. After installing the brass inserts (just pushed them in – no glue) I fitted the plates. I wanted to remove material from the plates that might interfere with the motor/chassis so I marked and removed the plates to do so, then gave them a final sand and re-installed.

The Chassis (next post)…

The Happy Canadian Scale Modeler!

[Ken]

Nice work! I saw the chassis run today and it’s nothing short of a bullet!

It’s going to be hard to beat. I look forward to seeing it race.

[Arthur]

Cheers!

The Chassis (Part I)

Since this will be a sidewinder and the motor bracket will be the most important part of the chassis to get right that’s where I start. I don’t worry about the rest of the chassis yet. One thing at a time.

I scavenged a press on nylon 15T pinion (that has what looks to be a close enough pitch) from something I threw out years ago – now it comes in handy – so that was carefully glued and pressed onto the can side shaft leaving a slight amount of clearance. Since this is a low power motor I applied a tiny amount of Gorilla Super Glue to the tip of the motor shaft before quickly pushing the gear on – which should work fine in this application if done carefully. Since space is tight underneath the body and the spur gear would need to be right up against the motor I placed the pinion very close to the motor bushing leaving sufficient clearance to account for the thickness of the motor bracket (.032″). This was set aside to dry completely before I trimmed the excess boss from the outboard side of the pinion using a fine file while the motor was powered. This was done because I knew I needed enough clearance for the rear tire. [Cutting the shaft shorter was another option but I wanted to keep as much surface area for the inner race of the pinion since it would just be pressure fit/glued in place – had this been a brass/steel pinion soldered in place I would have cut the motor shaft.]

I then secure a dummy identical BWNC1 motor to a bracket which I made earlier. Using two ‘U’ shaped wires (.062″) I lock the bottom of the motor in place making sure the wire is very snug against the motor endbell. This will create a ‘snap fit’.

After this motor bracket is finished I need to align the drive side bushing. I remove the dummy, clean the bracket and then secure the motor with pinion to sort out the mesh. A Parma square oilite bushing will be mounted nearly flush with the bracket but only after I grind away most of one side of the bushing for proper mesh. Using the jig, rear axle pin and spur gear I check the size of the gap needed between the axle and the motor bracket and try different wire shims until I am happy with the spacing/mesh. With the bushing and wire shim cut/trimmed I remove the motor and gear and place the motor bracket back in the jig and solder the all three parts together making sure the motor is parallel with the rear axle pin and nearly flush with the face of the bracket.

Now I figure out how far outbound I can mount the opposite bushing. Since clearance with the motor isn’t an issue this bushing doesn’t need grinding. By my calculations 35mm across at the rear minus 4mm for the spur gear minus 1mm for washers/spacers leaves me approximately 30mm across – but I will be cautious and give myself even more wiggle space. Using more wire wrapped around the bracket I solder in the second bushing: Then I secure both bushings to the rear of the bracket with more wire. I use two separate pieces of wire, one for each bushing:

Finally I add another wire at the top in between the bushings to prevent any deflection. The bracket itself is done and cleaned.

Jig Setup

Time to start on the chassis. My finished wheels measure 20.5mm x 7.5mm (they are actually a touch (or hair) more than 20.5mm which gives me some wiggle room). The other basic dimensions for my chassis – I measure the body leaving a few mm’s clearance for the width of rolling assemblies (err on the narrower since it is easier adding spacers). We already used the rear rolling assembly measurements when making the bracket… My form is handy for this.

For this Lotus 30 body my basic chassis dimensions were measured to be:

• Front Axle Total Width: 48mm (33mm);
• Rear Axle Total Width: 50mm (35mm);
• Wheelbase: 73mm;
• Distance of Guide to Rear Axle: 85mm;

Now I set up my jig according to the above. As for chassis clearance I am aiming for a hair more than 2mm since this will accommodate the guide and give me good overall performance so I select the front and rear wheel blocks accordingly. After I set up the jig I always fit the body over everything to double check the position of the guide and axles. If it looks good then we are ready to measure, bend and solder the rest of the chassis together (Part II).

 

 

The Happy Canadian Scale Modeler!

[Arthur]

The Chassis (Part II)

Since this is a ‘low power’ chassis it will be kept light. The finished and cleaned rear motor pod was yet again secured in the jig.

I fabricated the front tongue from .032″ brass plate and soldered a 4.5mm diameter brass tube into the hole, angled slightly back, to accommodate a salvaged guide from some RTR model. In the past I’ve sleeved two brass tubes and drilled them out to get a precise fit around the guide post but I’ve found that a little sideways guide movement doesn’t hurt as long as it doesn’t tilt in the post sleeve – to avoid this make sure there is no vertical guide movement… but that’s a subject for another topic/thread…

I set my jig’s guide post at the correct distance – double checking with the body – and place the guide plate (tongue) on the jig. So now I need to join the two parts. Later the front axle sleeves and body/plates will be soldered to the tongue. Since I wanted to do a torsion chassis whereby the front assembly rotates in relation to the rear assembly I would connect the two parts using just a single sleeved central backbone. I opted to use 3/32″ piano wire for this which is a little heavier but will minimize deflection. I used 1/8″ brass tube to sleeve the back portion. Since I wanted everything to lie flat on the block – because the 1/8″ brass tube is not as thick as the tongue – I filed down the underside of the piano wire which would be soldered to the tongue. When I was satisfied with the height of the wire/sleeve (that they were parallel with the block) I tacked it into place on the tongue and then bent and soldered the two “L” shaped wires to secure the sleeve to the rear end. After securing the sleeve I went back and finished soldering the front of the wire to the rest of the tongue.

I opted to use .032″ wire to join the two halves of the chassis and to dampen the rotation of the two parts – which at the rear would be soldered to the sides of the motor pod and at the front inserted into a pair of 1/16″ brass tubes soldered to the sides of the tongue. I opted to bend the wire to account for the narrower tongue. Whether or not you bend the wires you MUST ensure that they are parallel with the base of the chassis to ensure the geometry of the front and rear halves is flat at rest (without any load). If you pick up the chassis and the front half twists slightly that is no good. When both halves of this chassis are finished & cleaned I’ll solder the wires into the 1/16″ brass tubes to make it one. But before I do that I have two more things to solder to the tongue…

The Happy Canadian Scale Modeler!

[racer68]

Thank you Art for posting this step by step build. The level of detail in your photos answers a lot of my questions. The explanation of  the motor mount, bearings and the positioning on your jig will help me make a better chassis than I’ve been able to do before.

Cheers

Steve

[Arthur]

The Chassis (Part III)

I went with independent front stub axles up front and decided to throw in some negative camber as an experiment. I cut a pair of axles from 3/32″ piano wire (approx. 20mm in length) and soldered a No.2 steel washer on the end of each. I also cut 1/8″ brass tube in 15mm length to sleeve the stubs.

Setting the Jig:

I used two wheel blocks to set the angle of each sleeve, one larger, one smaller to give me the camber. I used the axle locating pins on the jig and slid a regular drill blank through both blocks untit the tips met at the centre above the chassis. The block which was butted up against the sleeve (on the outside where the wheel would rest) was the properly sized block for the wheels I selected. The larger block was placed against the outside of the pins and was set to give me the angle for the stub axle. There is no magic to the angle here – if it looked good then it was good. After eyeballing their alignment I soldered one “L” shaped piece of piano wire to support each sleeve. I then soldered another piece of piano wire to join the two sleeves – initially I did so across the top, making sure to leave enough clearance for the washer. [Later on I removed the top piece and used a “V” shape piece which was also soldered to the centre of the tongue to give the front axle a little more support.]

After soldering this you must make sure you have enough clearance to slide each stub axle into the appropriate sleeve from the inside out. I cleaned the front end again. Mounting the body is next.

The Chassis (Part IV)

Placing the chassis against the body in its correct position I sorted out the best location for the brass rod to which a straight hinge (using 1/16″ brass tube) would be soldered to each side plate. The purpose of the hinge is to facilitate body float. I decided to run the rod along the outside edge of the plate and solder the hinges on the inside face. Later on the height of the front or back of the body could be adjusted by simply bending the brass rod.

Before tacking in the hinge I assembled everything to make sure the wheels would be exactly where I wanted them. Because the pins can be pulled out from inside the hinge I was able to remove the chassis from the side plates… each pin is bent into a “U” shape and secured around the foremost screw. Urethane washers above and below each pin help maintain the movement of the pins underneath each screw head. The back of the pins were cut flush with the rearmost edge of the hinge so that nothing stuck out.

I took everything apart, cleaned the portions of the chassis that were soldered plus the side pans and reassembled for testing.

Wires were added. Here you can also see that I replaced the straight piece of piano wire holding the front sleeves with the “V” shaped wire secured to the centre of the chassis.

The wire here was too long and ran over the can of the motor – and underneath one of the side plates – which I found out during its debut interfered with body float (and stance) – so it was both shortened and made to run up the bell end side of the motor directly to the motor tabs. (to be continued…)

The Happy Canadian Scale Modeler!

[Joe]

Interesting  build Art. I’m not sure about the Neg. Camber setting for the front wheels since they don’t turn like in a real car application to increase the contact patch during cornering are you  doing it to reduce rolling resistance of the front tires or contact patch in corners.In the slot car application the front tires act as a stabilizing factor in turns to prevent tipping, I guess this chassis design allows for some articulation of the front axle but would not  taper cutting the front tires  create the same effect. :unsure:

In the total axle width measurements you have two numbers what due smaller numbers in the brackets represent the larger number is the track width inside the body?

Joe

 

[Arthur]

Hi Joe, I tend to agree with you. Regardless, since I was planning on doing independent stub axles for the front I decided to try the negative camber as an experiment since at worst it couldn’t hurt and to my eye I think it looks really good. I hope to make several more models using this front wheel setup and time will tell. With where I find myself in the hobby doing these sorts of things helps keep me interested.

The numbers in brackets are the widths in between the wheels so I know how wide to set up bushings or sleeves – and they are on the conservative side.

Cheers!

 

The Happy Canadian Scale Modeler!

[Arthur]

Back to the shell…

Since I was doing a period fantasy build and therefore could freelance a little I opted to use the taller stacks plus the tailpipes up through the bodywork. I cut out the openings for both – using a hand chuck and small drill bit.

I also opted for the small hoop roll bar and drilled holes for it. I made a few channels underneath the holes to make sure the hoop stood as straight as possible… 

The plan will be to glue all of these parts in place after paint, along with the rest – wrap around windscreen with mirror, interior details (including full pilot) and tail lights.

Paint

Now the body is ready for paint. I gave the body and parts a good scrub using a very diluted mixture of super clean and water. Then using my compressor I blew the body dry and let it sit for a bit. I would prime it first in white using Tamiya fine surface primer – after heating the can up in the sink with hot water… I sprayed a couple of light coats and then one final coat, checked for any blemishes and then hung the body to dry. I let the primer dry for 36 hours.

I would give this body a white stripe down the centre so I masked the stripe using Tamiya tape. I planned to use a white rondel for the number on the front but for the numbers on the rear quarter panels I would also make them white so I masked them too.

I decided at the last minute to paint this body black using Tamiya TS-14. Heating the can I gave the body a light coat to make sure there was no bleed under the tape – then a moderate coat and finally a pretty heavy coat – waiting about 10 minutes in between coats. I hung the body to dry for a few hours before removing the tape. Nothing had bled so I left it to dry for another 36 hours – hanging it above my workbench in the warmth of 4 four light bulbs the duration. [FYI: Had there been any bleeding at this stage I would have continued spraying it all black.]

Then I heated and sprayed a clear coat of Tamiya TS-13 – one moderate then one heavy and again, set it aside to dry among the bulbs. I took the lazy route and didn’t sand at all. Everything looked good.

The next morning I checked on the paint and there were a few runs in the black caused by the clear – likely because I hadn’t let the black cure fully. Not too big a deal since I could cover those small spots up with decals – but lesson learned.

While the body was drying I used Krylon Chrome to spray the tail pipes, intake stacks, inserts and separate knock offs. Since I was using the smaller wheels I needed to use the four spoke insert (375MCL4SPCA). I also cut off the knock offs from another set of inserts which I planned to glue into place at the end.

That would conclude the rattle can effort… next up – painting by numbers…

The Happy Canadian Scale Modeler!

[Arthur]

Hand painted details

The rest of the parts were painted by brush using Tamiya acrylics and Citadel washes. Some were primed with white primer.

The base of the tailpipes were given a blue wash using a diluted Tamiya metallic blue. The base of the intake was washed with undiluted Citadel paint, which sits nicely in all of the depressions to bring out the relief.

The inside of each exhaust pipe was also given a liberal application of Citadel wash… then the Molotow chrome marker was used on the tips of the exhaust pipes and the intake stacks by dabbing it until an even ring of chrome paint was applied to each circle edge. After both parts dried overnight they were dipped in Pledge acrylic floor polish to seal the paint. Both were glued in place using 5 minute clear epoxy.

The pair of tail lamps, mirror and windscreen were also dipped in Pledge floor polish. Before sealing the whole mirror casing I painted the round mirror dark grey. While the Pledge was drying I gave the seats a flat black wash, using Tamiya flat black acrylic diluted quite a bit with Tamiya Acrylic thinner. I added the shifter and linkage and secured the gauges – I cut off and used the tops of various gas caps. After painting the steering wheel, pilot and pilot’s head and test fitting them in the cockpit I glued the steering wheel into the pilot’s hands, shortened the steering wheel shaft and glued the pilot’s body to the seat with 5 minute clear epoxy. Next I cut off the mounting post for the pilot’s head and glued it in place.

The swiss cross and two stripes on Siffert’s helmet are white decals – when I applied them they naturally curved and joined in the centre at the back of his helmet – and while not entirely accurate – I left it as is – since I thought it looked good – sometimes you are better just leaving things alone. Next in went the fire extinguisher (even if they didn’t carry one in 1964) and the roll bar. Then the tail lamps, windscreen and mirror – all with the same clear epoxy.

The gap between the windscreen & body was covered with two thin strips of nylon tent repair tape – I use a sharp box cutter blade with a hammer to slice the sections. I find the adhesive to be more than adequate to secure the tape permanently.

Here is the tape on the windscreen – it is navy blue and I left it that colour but it can be painted if necessary.

Turning back to the inserts – using the Molotow I painted the raised centre portion of each spoke and the knock offs. The centre of each wheel was given a gun metal wash, then the inserts were fixed in place using a little white glue. The knock offs were added and fixed in place with clear epoxy. 

I mentioned earlier that I shortened and re positioned the lead wires.

The complete body now weighs 18.6g and the total weight is 76.8g.

A note about the decals:

The J. Siffert decals at the rear are Pattos peel & stick, so is the Lotus emblem at the front. The rondel on the front is from Monogram (two were used, one on top of the other for opacity) and the #11 on the rondel was a “0” that I printed using my inkjet printer on clear decal paper (cutting off the top and bottom) and sealed with Krylon Crystal Clear. The Champion decal on the nose is also inkjet printed while the smaller STP, Firestone and Champion decals on the sides are from Monogram. The white #11 decals on each side were cut from Testor’s white decal paper.

Regarding performance:

To say I’m pleased would be an understatement. While the gearing leaves speed on the table the cornering is exceptional. This car will not de slot and even after one race and more than 200 laps I have yet to find the limits of this chassis. Who knows how much of a difference the front end makes, if any. It is smooth, shiny and quiet and now my favourite one – till the next one at least…  :good:

The Happy Canadian Scale Modeler!

[Ken]

Art,

Your attention to detail is second to none. The body kit and the build are both works of art!  :good:

Thank you for explaining every detail. The bar has been set somewhere in the clouds. I doubt anyone will surpass it. But it will be fun trying.

[Arthur]

Cheers Ken!

To my eye the Hawk body is a touch smaller and more shapely than the Strombecker which makes it a wonderful platform – but not without its challenges.

Following Up:

A little tweaking this week and the car became 2/10’s faster than on Monday. Then, as an experiment, I took away the negative camber and slight toe out (keeping the same stub axle setup) and re-tested the model. There was no change in overall performance or lap time. I suspect replacing the stubs with a solid axle would reduce friction if it stays this way, but…

I plan to go back to the negative camber since I like the look regardless of performance – but this time I’ll move the sleeves slightly further apart… stay tuned…

The Happy Canadian Scale Modeler!

[Arthur]

Since I’m going to be taking the front end apart again I will also true the fronts down a bit and remove the spacer under the guide to lower the front of the chassis, plus since the front wheels will be a bit smaller lower the front of the body too… It is nice having those options when you originally build and err on the cautious side… 

The Happy Canadian Scale Modeler!

[Author]

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