Monday 18 January 2021

The XV sidecar - start of making a sidecar subframe and a plethora of other things (pt. 5)

Let's start with the biggest morale booster aside from firing up a bike for the first time and that's being able to sit on it for the first time. 


Assembling the bike up to a certain point has definitely been necessary, but the fitting of the tank (when the picture was taken) was hopelessly premature. But then again it felt incredibly good to sit on the bike.

The sidecar-swingarm-wheel-axle is about the right length and also 20mm so the wheel went straight on.

Laying out the sidecar - I wanted to stay within a track width of 1200 - 1300mm, sidecar wheel lead of about 300mm and about 15-20mm of toe-in.

The numbers achievable without any incredible handstands are 1280mm track and a lead of about 320-330mm. Toe-in will be set once the actual bike is built, but I plan to build it with 0 frame-wise, so I can set it up as I please once it is done.

Next job was to tram my milling vise and make the first bits in the lathe and mill. 

Added some pads to have more contact-area between frame and subframe-mounts.

Obviously the roundstock needed some flats for the nuts to sit on.

The adapter installed on the front cylinderhead.

Originally I wanted my bends to follow my engine very tightly, but to be fair, it would probably have given me next to no benefits in rigidity and less more work and the problem areas with the exhaust would not have been addressed this way.

I said, I wouldn't TIG-weld the subframe and guess what... here I am happily TIG'ing away.

Just to give you an idea of the size of my workshop... that's a 3m bit of tube. Cutting stuff got a bit tricky at times.

And here's one of the two downtubes (test-)fitted to the adapter.

The lower mount will be included (boxed in) into the downtubes. Due to lockdown I had to turn down 35mm roundstock to 24 over a length of 130mm. Definitely not a fun job as due to the cold the belts in my lathe are rather slippy.

Then I realised that in order to work out where the rear lower sidecar mount would go, I would have to fit the mufflers as it feels like everything is fighting for the same spots on the bike.  

In the past, I would simply have cut off a bit of M8 all-thread, drilled and tapped my mufflers and then welded them in. But not this time. Now as you surely know, stainless has the nasty habit of eating taps for breakfast and my M8 tap is as dull as can be. So I drilled 6.5mm holes (after fruitlessly trying to tap into the exhaust) and turned the stubs to 6.55, so they would be a gentle press fit and then welded them in. 

And there you go. She's looking more and more like an actual motorcycle every time.  

So what's next?  I need another spacer for the lower front mount on the other side and then this section can be completed rather quickly. After that the sidecar frame will (for the first time) get attached to the bike and then I'll see what the lower rear mount has in store for me. Lower frame and center-stand will undoubtedly need a modification and now that I know how the lower front mount is supposed to work I know I will be able to fit an oil-pressure sensor to the engine case. (I dreaded it would get in the way of the spacer.) Unfortunately this means the engine has to come out once more and I have to do some aluminium welding to fit the bung.

Friday 8 January 2021

Estimating horsepower via aerodynamic drag

I lately had some fun and felt in the mood for playing around with numbers a bit. The idea was that highest achievable top speed is relatively easy to measure and even though there's a series of factors at work, the main being aerodynamic drag. 

The idea is, when your bike achieves topspeed on level ground this is when its horsepower and the force working against it, even out. So with the topspeed v^2 being known, rho is generally assumed to be 1.2 for air and the only number I was able to find for Cd for a motorcycle was 1.8. You can play around with the cross-sectional area a bit, but a frontal shot of the bike with yourself on it should give you a pretty good idea. I ended up estimating it to around 1.3m2 for my TR1 with me on top of it. 

So I played around with a spreadsheet a bit entered the numbers as above and lo-and-behold got some numbers.

A whopping 71hp at the wheel (casually rounded up for bragging rights), which funnily enough is spot on with what the factory claimed for a TR1... Now I know that my calculation figures in 10 percent transmission losses, but no frictional losses, which at this point might be quite some, especially considering the skinny rear tyre, so the power-rating at the crank might be rather irrelevant. 

Really curious what the dyno will spit out and show whether this is a usable approximation or not.

Friday 1 January 2021

Project outlook 2021

This is less of a new year's resolution and more an attempt to plan for what to do in the coming year. 

Let's start with my own bikes:

XV-sidecar (still unnamed)

Obviously finishing the XV sidecar will be a priority for the first one or two months of 2021. At the point of writing it's on its wheels and I plan to do a swan-dive into building a subframe and subsequently an exhaust for it. Geometry-wise (as some will ask surely): track-width is between 125 and 130cm, lead is spot on 30cm and toe in is 5cm on 250cm and yes the sidecar will be unbraked. Never needed it on the XS-Triple-sidecar anyway.

Bumblebee the Everyday-TR1

Will get a new exhaust, because the ever-so-social Mr. Nick has bought my current one. The new exhaust will be more or less be the same as the current one, but I will also build a second center section with t a bigger diameter in an attempt to increase top-end performance a bit more. Also I have a reground camshaft from Webcam coming in some time in January and I am currently rebuilding a set of XV750SE heads, which I want to weld up and modify to have a 3 degree angle on the squish-band. The idea behind that is, I could increase the compression a bit and still get away with regular fuel. Other than that just some maintenance like a new brake-pump and a fork service and obviously repainting the fuel tank.


This will be a bit of a bigger project. I am starting to lean towards installing the old 500 4-valve for now to make it usable again as overall the performance of the 600 left a lot to be desired even with all the new components. I fully expect the Wiseco 96mm piston to be kaput, I really just hope it's not the crank that has taken a hit. Aside form that I have all the tubing to make a proper pannier rack for it and most likely I'll switch the harder Tenere shock back for a softer (lower-mileage) XT shock.


On the penultimate day of 2020 I received a parcel, which said "Hydraulic Press 12T" on the outside, so I guess, I'll have to make some tooling and finally get that crank done and then throw the bike together and see how it goes. I might actually consider selling this one or convert it to be at least theoretically usable on the road.

Turbo TR1

I bought an AMR500 for it and I still have enough parts to make a new Turbo-Kit. I guess this will be a Summer project, unfortunately I have to admit this has to take a bit of a backseat compared to some other stuff.

XS Triple Sidecar

Once the new XV-side is up and running this one will be for sale including a lot of the parts that I have for it. (Some interchange with XV and RD stuff, those parts will obviously stay.) The engine needs a bit of a cleanup and the bike some cosmetics before being sold off, but other than that she was a good girl for the time being.

And then there's a shorter list of my dad's stuff that I want to take care of, which is a bit shorter in the number of items, but the actual work is probably not to be underestimated.


My dad's Bandit 1200 is due a proper service incl. adjusting all of the valves and I secretly hope we can get away with not overhauling the 6-piston Tokicos for another year, because the bill for all the parts required would be rather hefty. 

Goldwing 1200

This needs assembly and then an exhaust by yours truly. It's really more a case of "get your arse up 'n' do it" kind of jobs. One of the bigger tasks will be to get rid of the integral brakes as neither my dad nor me kind of like those a lot. 


I have to get a set of VM34s and make a decent stainless exhaust for it. The suspension is a lot better than I initially gave it credit for, but the engine is massively strangled by its stock components at the moment. The ignitech helped a little with the power curve and as such I somehow foresee, I'll daily this for a few weeks at some point to dial it in with the new carbs. (It's a fun little bike, once you simply accept the fact that you absolutely have to thrash it, like it is going out of style, it's even rightfully considered quick.)

Moto 6.5

Should be good apart from sorting out the battery drain issue.

Pretty one (XT 500 4 valve)

Could probably do with a service, but other than that I consider this one to be in perfectly usable shape with little to do in terms aside from a bit of regular maintenance.

Other projects on the list:

A new workbench

My current setup is cobbled together from my old workbench (good) and a folding table (terrible), which doesn't lock very well and is wobbly as sh*t. Also there's about one extra meter of workbench I can fit in there and that's a world's difference, if you only have around three meters in total at the moment.

A new mill

I have set my eye on the ZX7045's little brother, which is mostly identical except for a MT3 spindle, which would allow me to re-use my tooling. As it has the same footprint and mounting hole pattern it should simply fit on my current stand. Admittedly I am also constantly on the lookout for some 626-type mill or something a bit older and less home-owner but the small and clever stuff rarely comes up for sale. 

Rhino lathe

Needs two new spindles for the cross slide. One is bent and both are imperial. You get used to it, but it's no fun working this way. Still debating with myself, if I shouldn't throw some paint on the old girl. 

Re-organize my spare part storage

When I moved in into my new workshop over a year ago, my dad donated quite a few storage trays. Unfortunately they are too small and too flimsy and the parts have to be grouped better as during the sidecar build I noticed that I have so far spent about five to six hours in total looking for parts that I absolutely knew I had.

So that's it for 2021 - should be plenty to keep me entertained. 😉