MS Excel roll centre calculator

Just put together a very simple roll centre calculator in Excel Online which should work for one axle of an RC car with double wishbone suspension.

You’re welcome to try it out yourself!

Roll centre calculator on OneDrive

 

Tamiya #42313 Large Shim Set for Gear Differentials

But first, a little background…

Effectively, I haven’t been racing for the past 3 years. Personal circumstances and choices meant I could’t attend club races regularly, and because I wasn’t racing regularly, I felt less inclined to attend the bigger events.

Last year, I tried to race in the Iconic Cup, and for whatever reason I had lots of problems, and didn’t achieve what I felt I should have done.

This winter, I tried again with the CWIC XRS (run by the Chippenham club). Again, lots of problems with the car, combined with being well off the pace.

I would be intrigued to know what is the root cause of the problems – lack of practice, my increasing age, outdated equipment, or simply a lack of motivation. Sadly, I don’t know the answer.

What I do know (and this is what leads me on the the real topic of this post), is that if you under-perform, you end up in races that you shouldn’t be in, where driving etiquette appears optional. And you get battered.

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I am still running my Tamiya/Samix TRF418 with the 419 rear diff. It is a car I have struggled with on many occasions. As the winter progressed, I managed to get a degree of consistency out of it on the new-to-me Hudy tyres and ETS carpet. Unfortunately, consistency doesn’t count for much when you get punted repeatedly by lapped traffic.

The rear diff broke – breaking an input gear and coning the shims.

While searching for some replacement parts, I spotted these:

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The set includes 2x 0.3mm shims to go behind the input gears, 2x finer 0.1mm shims for the same location, and 4x 0.1mm shims to go behind the spider gears. As these shims are the same size as the gears themselves, loading should be much more even, reducing the tendency for the shims to cone. Also, the large size should make it harder for oil to find it’s way through the seals, reducing leaks. We’ll see if this works out in practice.

In terms of re-assembling the diff, I always shim the input gear so that it rotates smoothly with minimal backlash. Just one 0.3mm shim was enough for this on both sides. I will reappraise the shimming next time I have the diff apart.

I also put a 0.1mm shim behind each of the spider gears, and assembled the diff dry to make sure everything worked smoothly, again with minimal backlash. It did, so I filled the diff with oil (#2000 for now) and put it back in the car.

I have to say that I don’t buy in to any of the diff-building “voodoo” that you may read about elsewhere. Tamiya’s parts are fundamentally good quality. I don’t sand down the gears, I don’t weigh the oil, I don’t use special slime on the seals. I just lube the seals with the normal silicone oil, make sure there is no flash on the gears, and fill the diff until the fluid sits just above the cross shafts.

Plan is to get this on the track again this week and see if it runs properly again. Will be glad to put this winter’s racing behind me!

 

Diagnosis: Puncture

(with apologies to Dick Van Dyke)

Punctures are frustrating.

But what can be even more frustrating is working out why they happen. And why they didn’t used to happen. And why they seem to be affecting perfectly good tyres and inner tubes…

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Giant S-RX4 tyres

My bike left the factory with these Giant S-RX4 tyres. They are a pretty high-volume hybrid tyre at 700x40c, and for well over 6 months and 1,000+ miles of city riding they did not cause me a single problem.

Then one day, I got a puncture. OK, these things happen, and it is pretty easy to repair.

Two weeks later, I got another puncture. I guess there must be a lot of debris on the streets at the moment.

The following week, another puncture. Starting to get a bit frustrating.

The next week  – two punctures – one of them on a family trail which could have easily spoiled the whole day (fortunately I had a spare inner tube after the previous repairs).

I really needed to work out what the problem was.

What I found strange was that the tyres did not have a huge mileage on them, and there was still plenty of visible tread. But then I noticed that small chunks of glass were getting embedded in the tread (and I mean really small – only a few millimetres across).

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You can just about see the tiny chunk of glass in the centre of the tread

It wasn’t taking much for these small chunks of glass to work their way through to the inside of the carcass, puncturing the inner tube.

But why was this happening now and not in the previous 1,000 miles?

Well, pliers and scissors helped to explain why…

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Cross section of the tyre

Put simply – the tyre is pretty thin and there doesn’t appear to be any form of puncture protection.

The rubber has worn down and is less than 3mm thick along the centre of the tread ( decreasing to 2mm at the edges). No wonder a 3mm chunk of glass can penetrate the carcass!

Goes to show that even a tyre with a visible tread pattern could be worn beyond its useful life.

Naturally, I decided that I had to buy some new tyres.

The two most popular puncture-protected brands seemed to be Continental and Schwalbe. You can normally count on German engineering. I chose the cheapest ones I could find and settled on the Continental Contact II.

While I was waiting for them to arrive, I got another FOUR punctures in just one week!

Fortunately, the Continental’s have yet to cause me a single problem. And I daresay that they feel a little faster!

A blast from the past

I have too much stuff. I need to get rid of some of it. So I’m in the middle of a bit of a clear-out.

One of the boxes I hadn’t looked at for the past decade or more contained some RC magazines. They are a nice reminder of three phases of my RC history…

Phase 1: The beginning

The name of this blog is a bit of a giveaway, but my first “real” RC car was a Tamiya Super Sabre. I remember owning the Radio Control Model Cars issue that included a review of the car at the time, and when eBay opened up people’s collections of old stuff to a wider audience, I was able to get hold of both the RCMC and Radio Race Car review issues. Thumbing through these is a trip down memory lane on so many levels.

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Phase 2: The blogger

I first started “blogging” in about 2002 (when it probably wasn’t even called blogging), but my personal website at the time (now long since deleted) became something of a go-to destination for information about the Yokomo MR-4BC. This was in a period when 4wd buggy racing suffered from poor turnouts and there was a lack of people at the tracks who you could share information with. Fortunately, the internet changed that. I picked up as many magazine reviews of the MR-4BC as I could, including a back issue of Radio Control Car Action’s review from the USA.

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Now it has to be said that the MR-4BC was not a very good buggy, and although it ran well at the smooth indoor track I raced at at the time, it was not a match for something like a Losi XX-4 outdoors. In fact very little was a match for the Losi XX-4 until the JConcepts BJ4 came along. But I enjoyed running it.

Phase 3: The businessman

I came to a point in my then-career where I was only getting offered short term contracts or freelance work, and was faced with a dilemma. Do I move to a new area to find more job security, or do I take a risk on setting up in business for myself and take control of my job security? I chose the latter, and for about three years ran my own RC business and made an honest living out of it.

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Marketing is critical to any business, and editorial coverage is worth a lot more than advertising space. So, in the early days, I would keep a copy of each of the magazines I managed to get a little editorial coverage in – this small collection of Radio Race Cars, Racers and a Maxbashing is a nice memento of that time. They don’t trigger the same kind of memories as the magazines from the 80s though – I feel as though the world changed a lot more between 1987 and 2002 than it has done between 2002 and 2017, but that could just be the difference between childhood memories and the ones of an adult.

If anyone has a particular interest in the magazines from the noughties, let me know. I’ll be keeping the ones from the 80s.

Dave

I heart IKEA

You know what, I REALLY like building IKEA furniture.

A change of circumstances recently means that I have furnished a two-bedroom house from scratch, and almost all of the contents have come from IKEA.

The experience of building IKEA furniture has a lot in common with building a Lego set or Tamiya kit:

  • The quality of manufacture is exceptional. You almost never get a faulty component or a missing part. I can think of only two items that have caused me trouble in 15-odd years, an “Aspelund” wardrobe mirror and bed frame, both of which are still in use today after a few tweaks and three house moves.
  • The packaging is ingenious. It is much more than just a set of parts. Just as much thought goes into the packaging materials themselves, and even the design of the furniture itself to allow it to be flat-packed. As a single example, the “Kallax” drawers use a one-piece folding hardboard insert to create the structure for the drawer runners.
  • There is a unique design language. You can always tell a Lego set from brick-a-like alternatives, and you can always tell a Tamiya kit from the rest. IKEA’s designs are frankly weird at times, but somehow it emboldens you to try something different. More often than not, the weird design works.

By way of contrast, the Argos TV stand I bought was little more than a set of boards and some dowels.

It may seem strange to say this, but I would happily build IKEA furniture all day long!

Reflections on the Iconic Cup

Sometimes life challenges you at work.

Sometimes life challenges you in your relationships.

And sometimes, life challenges you in your hobbies…

 

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As the car came off the track at West London

I’ll start with the positives from the 2017 Iconic Cup. I was racing with a great bunch of clubmates; it was great to see so many “scale” RC cars going around the track; and we were blessed with some unseasonably good weather.

But I had SO many problems!

Many years ago, I was (trying) to race a Kyosho Lazer ZX-5 in the North East regional series. I was well out of practice off-road, and the Lazer was not an easy car for the conditions. After getting thoroughly soaked at Batley, I gave up. It wasn’t fun.

I was moments away from giving up on the Iconic Cup on several occasions.

The biggest problem I had was with the drivetrain of my TT-01E. Many years ago I had a normal TT-01 and it caused me no problems whatsoever. This car was different.

It ran perfectly indoors with the 58T spur gear, but when I put the 55T spur gear on for outdoors, the problems began.

First race of the series was at Stafford – a track I have never been to. My first run was good enough for about 6th overall, but the car was slowing towards the end of the run. I spent the rest of the day trying to find some pace again, and realised that I had not located the pin into the 55T spur gear properly which had caused it to melt onto the spacer that is supposed to stop it from sliding off the pin. I repaired it as best I could, but didn’t solve my problems as I had cooked the Sport Tuned motor at the same time. Fortunately a racing buddy had a spare Sport Tuned, and I fitted that to have a bit of power for the final (having slipped down to 11th in the order). It was a fun race with a couple of late challenges making the win from pole feel all the sweeter.

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Torque Tuned is the only motor I have left

Second round was at my “local” track of Cotswold. This is a power track for any class. Naturally, I melted the replacement spur gear and blew another Sport Tuned but chose not to replace it as I was already getting a bit fed up. I ended up last in the A.

For round 3 at Broxtowe, I rebuild the car with a new chassis, a new propellor shaft and input axles, a new spur cover and, naturally, a new spur gear. I tested the car indoors and it passed with flying colours. I even went to the track for Saturday practice as it is a long way from home and I decided to stay overnight.

I melted the spur gear in the first run.

I was about to go home, when another racer offered me his spare car. The generosity of his offer made me reconsider. Instead of taking him up on his offer, I kept running my own, damaged, car. After all, if it had melted and still runs, it isn’t going to get any worse. I had fitted a new motor for the meeting and surprisingly it had more or less survived, and I kept running for the rest of the meeting, ending up with my best result of the season with 6th. It’s a great track for the low-powered cars of the Iconic Cup.

With pretty low morale I turned up at West London with no intention of doing anything to the car. Before the day was out, my third Sport Tuned of the season had died, so I fitted the Torque Tuned that had come with the kit. A chat with a local suggested that the difference between the two motors was not so great, and he was right – I managed to finish 9th.

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The melted spur spacer (2nd time around)

That was the main frustration. I have an idea for a part that my Dad could turn on his lathe that should cure the spur gear issue for good. Of course, that would be outside of the rules as they are written.

I also struggled with tyres and the body – my ancient Sorex 32s just weren’t hooking up consistently; and the Diebels Alt 190E shell (which received many compliments) simply doesn’t handle. I ended up running my tatty HPI Lexus GS (which I bought as a practice shell for my kids).

I haven’t ruled out running the series again next year, but I will have to think carefully about whether I can keep the costs (and the frustrations) to a minimum next time around.

Done! My first plastic kit in ages!

I used to build quite a lot of plastic kits – pretty much exclusively Tamiya. But at the age of 11 I got my first proper RC car and plastic kits fell by the wayside. I do remember the sheet of hardboard that I had to build them on, and the “diorama” I once made of a Jeep that had crashed into a lamp-post to make up for the fact that the bonnet of the kit was a bad moulding.

I tried to build a kit again about 10 years ago, but I didn’t have as much free time as I thought and RC got in the way again.

Finally, after a gap of 30-odd years, I have finally completed another kit. The kit itself was only about £15 – but the paints and accessories ended up costing several times more than that!

I had a few self-inflicted problems with the front mudguard which needed painting three times in total. There are a couple of other little mistakes, but overall I am pretty happy with the outcome.  It’s the Tamiya Honda CB750F kit it you hadn’t worked that out already.

The quality of the kit is amazing considering it was originally released over 35 years ago. One of the nice features of a bike is that lots of the components are visible. This is also one of the challenges!

Next kit has four wheels… just need to choose the colour scheme…