Dogbytes' R80 ST project

Some very good points being made there.

The bike will be considerably lighter than standard but it's a bit tricky to estimate by how much and it's effect on the CoG. For instance the engine is 50mm higher and 45mm forward of standard. There is a frame-mounted half fairing but no lights. And then there's the ever-increasing bulk of yours truly!

I have revisited the nether regions (no, not Holland!) and I do think that the battery might well be safe and fairly unobtrusive under the gearbox. It'll be pretty much hidden behind the sump.

When you're trying to get traction from a 200bhp motor in a 150kg bike piloted by a 65kg rider then weight distribution and, particularly, the need to be able to move it for and aft do truly take on a whole other meaning - and probably become more important to lap times than the speed at which the bike can be leant from the extreme at one side to the extreme at the other. In some ways, the more you try to specialise, the more you have to compromise. If I ever end up having those problems I will consider myself a lucky man!

However! I will have 85-90bhp to deal with. The bike, I would guess, will weigh around 160kg. The tyres (I got them today) are Dunlop TT100 GP - the special order sticky version of the old K81. The sizes are - 100/90x19 and 130/80x18. Me? 90-95kg geared up. I think it might stand up on its hind legs in the dry. A 50mm extension of the swing-arm would tame that. It would probably spin the back end up were I to take it out in the rain. But four-stroke twins can be nice that way and it might not. Single, twin-piston, caliper, (1970's tech) on a 260mm disc. Stoppies? I think not.

Anyway it'll be fun to see, it might surprise me. I'll still love it whatever it does.
 
The tyres (I got them today) are Dunlop TT100 GP - the special order sticky version of the old K81. The sizes are - 100/90x19 and 130/80x18. .

That sounds a nice plan as I'm torn on what tyres to go for…. looking period acceptable but all sticky? Are they road legal?
 
On the old triumph twin I'm building for track use, I put quite a bit of thought on the location of random things like coils, batteries, cdi, fuel, me….

I'm reducing weight where it's easy, but generally moving easily relocatable stuff upwards and forwards. It goes against the more traditional racing philosophy (which probably leaked out from car engineers) of chasing the lowest possible CoG, but is based upon the teachings of the late John Robinson (and his brilliant chassis book), and practical experience with a few bikes with radically different CoG.

My interpretation of John Robinson's principle (maybe wrong, but it works for me) is that when the CoG is just right (on the tyres and track it's intended for) the bike will move between wheelie and wheelspin (Stoppie or front skid) when your body movement is back or forwards. With CoG too low, like a drag bike on wet tarmac, it will wheelspin/skid the front or when it's too high, like a supermoto on dry tarmac it will always wheelie/stoppie.

Equally, the effect of CoG height on cornering is interesting when one does the maths (or tries changes in practice), particularly when tyres get wide and the displacement of the tyres 'point-of-contact' from the centreline is greater. My other Bonnie always locked the front (rather than stop pie) and never wheeled, so I reckoned I try to move the CoG up and forwards until I can lift the back wheel on the brakes.

It's all nonsense anyway of course, on Airheads/old triumphs, as normally the brakes don't work, the power is never that great and the tyres rarely wider than a 120 anyway, but it lets the rider think his bike is better (confidence is king) and I would still absolutely recommend John Robinson's 'Chassis Tuning' book.

This BM' is very light,fast and handles a treat.
I've just sold it-"Why?" I hear you ask...because I'm obviously very stupid!! :blast
 

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That sounds a nice plan as I'm torn on what tyres to go for…. looking period acceptable but all sticky? Are they road legal?

Yes they are road legal. They look like period Dunlop K81 TT100s but are, allegedly, stickier. Cheap they ain't, Michelin Pilot Road 4s for my K1300S are cheaper! I had TT100s on my Moto Guzzi Le Mans PR, back in the day, and they were okay - not my favourite, but okay. There's not the choice in those sizes these days. If I was building the bike purely for performance I'd change the rim sizes - but then, if I was building it purely for performance I'd be building something else! It's a shame they don't do a modern version of the K91 Red Arrow - my favourite tyre ever. If you ignore durability, that is...
 
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That is Sooo pretty!:thumb2
 
Yes they are road legal. They look like period Dunlop K81 TT100s but are, allegedly, stickier. Cheap they ain't, Michelin Pilot Road 4s for my K1300S are cheaper! I had TT100s on my Moto Guzzi Le Mans PR, back in the day, and they were okay - not my favourite, but okay. There's not the choice in those sizes these days..

Hmmmm… £74 and £98 at www.tyreleader.co.uk

Please hurry and get it rideable, and arrange for 3 identical bikes fitted with Avons, Conti Radials and the new 'ME1' style Metzeler Sportec Klassik; then write up a back-to-back test!:D
 
The red bike is lovely!

Tyre leader, I looked at but I was trying like hell to get as much done as possible this week - so I got my local tyre supplier to get them for me.

I'm off to Azerbaijan on Monday. Back sometime shortly after 20th April. Bike will be finished in June. I promise!

I'll have my laptop with me and will be drawing up various bits in CAD so I can email them to people and have them made whilst I'm away. I'd like to do it all myself but this has gone on long enough! There are other projects lining up...
 
I'm off to Azerbaijan on Monday. Back sometime shortly after 20th April. Bike will be finished in June. I promise!.

You'll have to take loads of new photos of the bike and bits before you go, so you can post one a day and keep the thread near the top. :D Enjoy Azerbaijan!
 
You'll have to take loads of new photos of the bike and bits before you go, so you can post one a day and keep the thread near the top. :D Enjoy Azerbaijan!

I have a couple of unpublished pics:)

I've also got a couple of CAD projects that I can upload pics of. There are bits I'd have liked to have made myself but can't due to time constraints. However I'm lucky in that I have friends who can machine components to a standard you wouldn't believe - think experimental fighter plane component standard.
I will do adjustable preload for the fork tops. I needed new spring retaining nuts anyway, so why not? I may also do the rearsets...

Things will pick up once I'm back (20th April, allegedly). I have someone who's anti-aircraft gun I've promised to look at, other than that it'll be 100% project bike!
 
Day of tomorrow!

I'll try to post some of the pics/info that I brought with me :)

I just this minute paid the Duty on the Toaster Tan top yoke and it should be delivered on Monday - I'll try to get the lovely Charlotte to take a couple of snaps. I'm looking forward to seeing that myself!
 
I'll try to post some of the pics/info that I brought with me :)

I just this minute paid the Duty on the Toaster Tan top yoke and it should be delivered on Monday - I'll try to get the lovely Charlotte to take a couple of snaps. I'm looking forward to seeing that myself!

I am in interested in getting one of these top yokes - might I ask roughly how much the duty was on it please? (you could PM if you dont want to broadcast)

Many thanks

:beerjug:
 
I am in interested in getting one of these top yokes - might I ask roughly how much the duty was on it please? (you could PM if you dont want to broadcast)

Many thanks

:beerjug:

Duty was £17.55 including handling. So not a deal-breaker. Service and communication from Stephen was superb. I've seen a pic of the yoke in it's unpolished state and it looks great - so I'm looking forward to seeing the finished item. Can't say for certain until then but it certainly looks like a quality product.
 
Duty was £17.55 including handling. So not a deal-breaker. Service and communication from Stephen was superb. I've seen a pic of the yoke in it's unpolished state and it looks great - so I'm looking forward to seeing the finished item. Can't say for certain until then but it certainly looks like a quality product.


Yep pretty reasonable really. Cheers!

:beerjug:
 
Perch

Okay, I left mere hours before this arrived so I too have only seen these pics!*

I made an aluminium seat base (previously reported) and sent it, after some discussion on the phone, to Dan at Bootleg Bike Seats in Preston. As with the yoke, I haven't seen it so the verdict will have to wait but the firm were extremely easy to deal with, very helpful with suggestions, prompt and on time. Very reasonable prices too. It's great to report good experiences!

The seat is covered in a firm closed-cell foam and then a waterproof Alcantara. I have to say, I think it looks great.

*(actually, Dan went to great effort to get it to me before I left for Azerbaijan and he succeeded too - by I was 'saying goodbye' to the lovely Charlotte and didn't hear the postman!)
 

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Adjustable pre-load sounds the dogs danglies....could be a market in that :thumb2

FlatRacer do something for the other Airheads but not the R45/65 or 80ST.

I'm half way through the CAD drawing and then I'll get to to my mate to machine the parts. I sent him the standard one and an old stanchion before I left so that he has a pattern to screw-cut to.

A simple one would be easy to make but not so easy to use - besides I want to do something a bit OTT. I'll also built in a spacer for the shorter, stiffer linear springs which should be winging their way from the US sometime soon.

Replicas could be made available...
 
Father forgive me for I have sinned

…it has been two weeks since my last post and I have done sweet FA!

Okay, I've been a bit remiss here, I intended to keep trickling out little snippets - pics, CAD drawings, etc. and I just haven't. I can't even claim overwork (I would, except that Charlie B, of this parish, is out here too so he'd grass me up!) but, you know how it is, you get back to the hotel, have a dirty gin and then, by the time you've Skyped SWMBO, it's time for bed. Good intentions eh?

So, I'll share my thoughts…
1. How is Ritchie doing with the motor and the gearbox? Must email him.
2. I still haven't sourced a 32:10 final drive.
3. My linear fork springs have arrived. I got them from a UK firm but they had to get them from their supplier in the US. The rate was a bit of an educated guess, fingers are crossed.
4. I have to finalise the design of the fork top nuts - inclusive of adjustable preload. And possibly a couple of pairs of spacers to get the, 35mm shorter, springs in the ride-height ballpark.
5. Have I forgotten to order anything important?
6. Chris 'Tunneruk' I will be contacting you again shortly about paint and electrics!
7. Starter motor - I still need to order a Valeo starter motor.
8. The top yoke arrived from Toaster Tan but SWMBO hasn't sent me a pic yet. I've only got the one of it in its unpolished state. may have to share that one…
9. Final drive coupling. still need to get that sorted out and machined up.
10. I have three weeks to get all of the above in place, before I'm back in the UK for a few weeks of frantic bike building - I want this up and running and finished by sometime in June.

Things I still have to have thoughts about…
1. Exhaust. Header diameters and lengths. Brackets for 'silencer' (snigger!) on seat subframe - when it's finished.
2. Battery. Where the hell do I put the battery?
3. Rearsets. I have to make them from scratch.


I should post a pic…
The Acewell instrument unit. Mainly a rev counter but it also serves a s a speedo to keep the MOT man happy.
The, at the time, unpolished top yoke.
The top of the forks with the gorgeous Woodcraft clip-ons. Obviously it'll look a lot better with the Toaster Tan top yoke which is patiently awaiting my return.

Okay, CAD sketches next time… :D
 

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