98cc

A couple of weeks ago it had its big debut at the the Vintage Revival event at the very historic Monthlery banked circuit in France. A couple of the other GN specials from the U.K. went over, GN Parker, GN thunder bug and the most legendary of them all GN Spider
These pics were taken when we had the body off Spider to do some adjustment to the clutch, it shows the standard position of the chains on the axle. Spider was built by a hillclimbing legend called Basil Davenport and held many records in period and would routinely beat far more advanced works cars like the ERAs, Maseratis and Bugatti’s of the time. The engine is a derivative of the lightly tuned 90 degree v twins that the road going GN came out with standard. Constantly developed by Basil turning it into the 1500cc methanol burning chain driven over head camshaft monster that it is now

Having now been in the U.K. for 3 years my ideas and inspirations have changed slightly from the wooden chassis cyclecar I had originally intended. I’ve been very lucky to get quite involved in the vintage racing scene over here and have made some very good friends because of it. A GN cycle car was always the dream although with none available in NZ to look at and the closest example being in Aus it was quite hard to fathom coming up with one. Since being over here I’ve managed to collect enough GN parts to put together this which is my take on the Hillclimb special concept of the 20s-30s. Going to all the swap meets in the calendar i managed to get hold of all the other groovy bits and pieces that I needed for the build. 

The defining feature of a GN is its chain drive transmission and solid back axle. 4 different ratios with dog selection. An incredibly simple but extremely effective system with large scope for easily changing ratios.  Normally on a GN these chains are on the back axle but on this car I’ve moved them forwards so they are under your legs, this means you can have a low down far back seating position that you can’t get with the chains on the axle.  Of course It needed a name to get the poms scratching their heads....

@Vintage Grumble Update, I built a thing 

Over to the mill to drill through stud holes.

Dividing head to do stud clearance cutouts

Repeat x 2 

Will need a final hone when the time comes otherwise finished 

@sr2 Good job keep it up. How are you planning on running the chain joining the engines and gearbox?

Heres my twin Villiers I built a few years ago. Had epic times hooning around Vegas drome for Dromeageddon mk2 

One year later......

So shortly after my post I packed my bags (including a JAP crankcase)  and hopped on a plane to the Uk on the big OE. I’m working in the vintage car world over here and have had some pretty amazing experiences. After spending so many hours looking at pics of cyclecars and the like it’s pretty neat to be at the events where they are running and get a real feel for them. One of the coolest trips I have been on was in Mark Walkers GN Thunderbug. A 4.2 litre Vtwin in a light weight chain drive chassis is definitely a good formula....

Some pics from the last year...

Have many more to put up.

With so many good vintage car events over here i need to get a car built so have been working flat out on the engine after hours and have made a fair bit of progress 

Cases bolted together and set up on the rotary table with a mandrel through the drive side bearing boss. Using the boring head to fly cut the decks 

Drilling and boring the cyl stud and follower holes prior to tapping 3/4“ 20 tpi cycle thread, mmmm lovely.....

After all holes drilled and tapped and cyl base spigots bored 

Next up barrels

On 14/04/2019 at 21:55, 63Ragtop said:

All right man, this thread just got real interesting real fast!! Not going to cast your own post one like ol' bert?

 

Cheers mate, na I think I will be doing some flicking through the Wiseco piston catalogue when it gets to that stage...

On 15/04/2019 at 11:55, SOHC said:

 

Here is the engine, it was built at Mcintosh racing,  it runs well, its around 1100cc, it dropped a valve when the retainer snapped in half but it was ok, I made the exhausts and oils lines, engine plates, mudguards, and half the shit on this bike. it has Hemmings heads, I know a guy who has a KTOR engine on the floor in his shed, I can put you in contact with people but you probable already know them?

 

We were going to use Iron head sportster flywheels with custom knife and fork rods but ended up using what it came with as it was ok, it has side by side rods and the drive side main shaft is very very small  

Wow awesome, would of been great working at Mcintosh. I think I saw that engine run a few years ago when I was visiting Ken.

Were the Hemmings heads original upgrade parts for sidevalve engines? I take it the guy with KTOR on the floor would never part with it?

I’ll be making my own flywheels with press fits throughout, will get a 1.5” dia drive mainshaft with the bearings in have. A bit better that the original..... 

Have got the timing side case machined to the same stage now. 

Facing the timing cover mating surface as first reference.

Flipped over and same stuff done as first half 

Internal features finished on both half’s.

And with a couple of bolts holding it together.  

Next job get the timing cover bolted on 

Did you ever see the engine run SOHC? 

A bit of info on this engine. It’s a 1930 JAP JTOR long stroke racing model of 1000cc. They were used in racing 3 wheel Morgan’s and Brough Superior motorcycles.  These v twins are very rare these days and are worth a large amount of money. Lucky a place in the UK has reproduced some accurate castings for anyone mad enough to try make their own. I will be changing a few things with this one to try and get a bit more capacity and power out of it. 

Made a start on machining the drive side crankcase half.

Bearing boss faced off to become the first reference surface 

Flipped over, mating surface faced and holes drilled.

Now clamped down with spacer blocks to machine inner surface and bearing bore

Inner features finished

Next up timing side

Nice cardboard box arrived from the UK.

JAP V twin engine kit set, some assembly required.....

Should keep me busy for a bit. 

Good progress on the front axle this weekend.

I'm doing a tubular GN style front axle the same as Bloody Mary had.

Axle end blanks. 4140

Outer profile milled and kingpin hole bored 

Ready to go in the axle tube 

The axle tube. 1 1/2''   4130 3/16 wall, should be strong enough.....

Axle end in. These will get brazed into the tube 

Complete axle 

And mock up, made a couple of temporary axle clamps to hang it off the springs. 

Bloody Marys front axle showing the Austin 7 front stubs and wheels

On 13/02/2019 at 19:35, rot808 said:

I hope you’re keeping the templates to make more for a new race class for surprise Chelsea sugar factory hill climbs haha

Yeah will definitely have to do a couple of early morning runs....

Have been working on getting a front axle put together. I’m using Austin 7 front drums and stubs. These needed a bit of a rebuild 

Reamed out the kingpin bushes with an adjustable reamer 

Set up the stubs in the mill, indicated the king pin to get them square. The dividing head was very good for this job 

The worn bottom surface that needs remachining 

 And after 

Then needed to make a couple of new kingpins to fit. 4140 bar stock 

Finished 

On 04/02/2019 at 21:14, Truenotch said:

It was great to see this at Leadfoot on Sunday! You've done a great job bringing it back! 

How did it run? I only saw you head up the hill once and was surprised that it wasn't crazily loud with non-muffled exhaust setup. 

 

 

 

Cheers Truenotch. Had a great time at Leadfoot, so good to get the car to a motorsport event again.  A few teething issues including the problem that i thought i fixed with the new diaphragms. I think the crankcase seals are toast and its lacking in crankcase compression. There was a lot of oily mess around the engine and i think the seals are the only place it could be coming from.

Also missed one run after i failed to make it out to the start. Fired up the motor on the dummy grid ready to drive out to the start line, selected first gear let the clutch out and oh shit i'm going backwards........ Bit odd as it has no reverse gear. It was making some bad noises in the gearbox and i thought it had done some major damage somehow. Pushed it back to the pits, had a think about it and started it up again. Turns out it somehow backfired on startup and started running backwards, all of the noises from the gearbox was just the gear set spinning in reverse..... 2 strokes eh,  Dennis had never had that happen to him. 

Yeah a few people made that comment about it not being as loud as they though it would of been. One of the theory's is that it was quite loud but nowhere near the level of some of the other cars going up the hill. A couple of those rotary's were extremely loud. 

On 07/02/2019 at 13:03, Testament said:

def favourite car/bathtub of the event so well done. was cool to meet old dennis too

still cant get over how tiny everything is, like 3/8" wheel stud or something haha

Cheers man, Yeah i brought Dennis along for the event. He had an amazing time and was awesome for him to see it going up the hill, was probably the first motorsport event hes been to in 20 years.  Yeah its miniature, all done to keep the weight down. Oh yeah got it on the scales,  only 330kgs!!!!! 

I see a camera on the fire wall, you better post some videos young man!

Also, where did you get that hat? I must have one.

Unfortunately the camera didn't work VG so no hill vids.  I was yarning to this young american dude at the event about the car and he was wearing the hat. Turns out hes super into 2 stroke dirt bikes in the states.  Asked him where i could get myself of those epic hats and he took it off and gave it to me. Complete GC, said he had got it at a motorcross event somewhere along the line. 

Wise words to live by. 

On 18/01/2019 at 06:35, sheepers said:

I really like what you're doing but for the love of Christ use metric. 

We left that fucking ridiculous imperial "system" in the 60's. 

No, It was the way the Grandad did it. I will only be using the finest selection of Whitworth and British Standard Fine hardware to......