I have titled this tread as "Cyclekart build Gold Coast Australia" because at this moment I don’t exactly know what we will end up building.
Our thoughts so far. As our family has been involved with the MG car club for 40+ plus years the initial thoughts was to build a pre-war MG. The MG K3 sprang to mind immediately, the other option is the NA – NB Magnettes. Either way I believe they will both look reasonably similar.

So far we have bought 4 17in wheels from the Honda CT110. In Australia we call it a “postie” bike as the Australia Post delivery guys ride them. The wheels weren’t too hard to find. All in very good condition.

I will have to study some drawings of MGs and existing Cyclekarts and massage them both together to see how the proportions work.

---

David

1960 MGA 1600 Convertible,
Gold Coast, Australia.



Edited 1 time(s). Last edit at 07/18/2012 06:52AM by DavidMGA1600.

Here is a quick sketch of the proportions for the Kart.
Two questions spring to mind.
What is the typical upper height of the top of the bonnet? 760mm (30in).
Steering wheel diameter? We have an original MGA steering wheel we will be cutting down to fit. The original wheel is 420mm (16.5in)dia. Its as tall as the wheels

---

David

1960 MGA 1600 Convertible,
Gold Coast, Australia.

Hi,

Not sure about the bonnet height (I can measure my car when I get home -- and which is the "bonnet" -- front, or rear? I guess front. Not sure if my kart is typical.

My steering wheel is 12 inches in diameter.

16.5 inches seems huge. You may have a problem getting your knees
under it (you mentioned cutting it down though, so maybe you've got
it covered.

The other thing I noticed about your kart drawing is the seat-back is
awfully close to the dashboard. What looks right on paper doesn't always
work in real life -- you can't just scale down a full size car because
you have to make sure the driver's compartment will not only fit you, but
will actually allow ingress and egress without having to bend your knees
backwards.

Two experiments I would advise before becoming too attached to a particular
design: 1) Measure the distance on your drawing between the seat back
and the steering wheel, then go out to a real car, and adjust the driver's
seat so the distance between the seat back and the steering wheel matches
your drawing, then try to get in the car and see what it feels like. I suspect
if you try this according to your drawing above, you will have a hard time
even getting into the car. Then you can adjust the seat to a more comfortable
position, then measure the distance, then adjust the drawing. 2) Before
building anything out of plywood, or whatever material you're going to use,
make the body out of cardboard to the same plan you intend to use, tape it
together and try to get in and out of it without pushing any of the cardboard
out of place.

I think everybody initially comes up with plans which have
the distance between steering wheel and seat back too short
because it's kind of what you get when you scale down a full
sized car, and it "looks right". I know I made the same mistake
and had to push my dashboard forward.
See: http://scaryreasoner.wordpress.com/2009/05/24/cyclekart-progress-may-24-2009-plywood-side-panels/ Doesn't seem to have wrecked the aesthetics of
the car.



That being said, there are a few things I would do differently on my
kart. I would have made the nose shorter. I made the nose longer than
normal, deliberately, because I thought it looked cool, but I think it
probably makes the kart drive worse than it would if it were shorter.
I would also have worked harder to make the engine farther forward
in the design (not ahead of the rear axle, like some of the gittreville
karts, but not as far aft of the rear axle as it is) and that would have
made the boattail shorter as well. Being the first (and only) one I've
done, how the back end would fit together was mysterious to me, so I
erred on the side of leaving too much room for everything, which made
the back end larger and longer than it needed to be (which does make it
easy to work on.)

I've posted this to the Library, it may help reduce some confusion in the future on this Forum

http://www.cyclekartclub.com/article/term-translation.html

Don't have much to add to the build comments, but the MG K3 is a gorgeous classic car especially in race trim!

Skye

---

Webmaster, The CycleKart Club

Stephen, In OZ the bonnet is the front over the engine. I would appreciate it if you could measure the height of the bonnet as i need an initial idea to start with.
Your right about the scale of the car. I did copy then stretch upwards till the bonnet line reached 760.
We will be cutting down the steering wheel and will start at 12in. Using an authentic wheel should add instant character.

Just had a look at my drawing and kinda looks more like the MG R type.

---

David

1960 MGA 1600 Convertible,
Gold Coast, Australia.

From the ground to the top of the radiator is 27 inches on my kart (just measured).

I realized that I have a scale drawing (sort of). The shaded blue area represents the plywood sides. I say "sort of", as there were some deviations from this drawing in the actual kart, but not too many, nor too important.



Each small square is 2 inches per side (each red square is one foot per side)

Oh, and here is the drawing before I adjusted it to allow reasonable ingress and egress:


You'll notice the drawing has the top of the radiator being about 28 inches. You'll also notice the slope of the top of the hood (bonnet) is not the same as the slope of the plywood (blue shaded area) in the drawing. In the real kart, due to the way I constructed the foam top of the hood, those two lines are parallel, which accounts for the missing inch.

Another technique which I used to establish scale of things is to examine photographs, esp. side views of karts on eg. cyclekarts.com, is to use the wheels as a reference. You *know* how big the wheels are, and you can use that to establish a scaling factor. So for example if the wheels with tires are X mm in diameter in realitiy, and in a photo they are Y diameter, then any measurmements from the photo can be scaled to reality by multiplying by (X/Y). This only works for photos taken straight on, from not too much of an angle, and preferable with a long lens, not a wide lens. It won't get you exact numbers, but it will get you in the ballpark. Some of the pictures on this page are good candidates for such analysis: http://cyclekarts.com/CK1106A.html



Edited 1 time(s). Last edit at 07/18/2012 07:18PM by smcameron.

Stephen,

I would like to overlay your drawing over mine. Looking at your drawing it would seem you have a 78in (1980mm)wheelbase.
Is that correct at seem to be very long. Mine is 66in (1675mm) as per the "cyclekart" wheelbase.

David.

---

David

1960 MGA 1600 Convertible,
Gold Coast, Australia.

Yep, my kart is extra long. As I said above, "That being said, there are a few things I would do differently on my kart. I would have made the nose shorter. I made the nose longer than normal, deliberately, because I thought it looked cool, but I think it probably makes the kart drive worse than it would if it were shorter."

So, I made my kart longer for the sake of aesthetics, but if I had it to do over again, I wouldn't have made it quite so long.

There is mention by Mike Stevenson (of the original cyclekart Stevenson's) of David Mysona's kart having to be shortened -- I think it is somewhat common when basing a design mainly on looks to make it a bit too long.

see comments: http://cyclekarting.com/cyclekarting/cycle-kart-engine/

"Good idea to keep the proportions in the cute-range. The P3 Alfa of Mr. Mysona started out too close to the original proportions and the wheelbase had to be shortened considerably to get it looking right for a CycleKart. He did such a nice job on the car, but it’s easy to get off at the outset.

Mike"

That being said, it's not a fatal error, it still drives ok, and is still fun. But I think it would not be competitive with most of the karts at gittreville.


OTOH... this maybe doesn't look so cool:


-- steve



Edited 3 time(s). Last edit at 07/19/2012 11:07PM by smcameron.

Steve,

I have revised my initial sketch a little bit to open the cockpit. Maybe I will have to shuffle by ideas once we start to cut timber and screw it together.
Your right though you cannot simply scale a real car down to size.
I have been watching your build youtube videos to pick up hints. One thing i would like to know is how the now driven rear wheel is fixed but spins free, this you dont cover.

David

I'm thinking the tail needs to be a little longer and the seat back a little higher.

---

David

1960 MGA 1600 Convertible,
Gold Coast, Australia.



Edited 1 time(s). Last edit at 07/28/2012 05:34AM by DavidMGA1600.

I'm not sure I understand the question. The driven wheel doesn't spin free. It's keyed to the axle, so when it spins, the axle, and the sprocket and brake disc which are attached to the axle also spin. The sprocket turns the chain, which turns the 10 tooth sprocket on the torque converter, which is connected by belt to the engine, so the engine turns... on this last point, the torque converter is a bit weird. At idle speeds or slower, the two pulleys of the torque converter size themselves (by means of springs and clever mechanism that I don't quite understand) such that the belt is just kind of loose -- so in this case, at idle speed or slower, or if the engine is off -- the driven sprocket is free to turn without the driving pulley turning -- so at idle speeds the torque converter is kind of "in neutral" and this means the kart can coast. Give the engine a little gas, and by centrifugal force the driving pulley starts to close up, and (somehow) grabs the belt. (exactly how the torque converter transitions from "neutral" with the belt being loose to "engaged" such that the driving pulley and the driven pulley both "grab" the belt, I'm not sure -- it's actually kind of mysterious now that I think about it.) In any case, it works. So, the magic is all in the torque converter, I guess? Much like a flux capacitor, the torque converter is what makes cyclekarts possible. Well, I think the driven pulley kind of always grabs the belt, but at idle the driving pulley opens up enough that it doesn't grab the belt. Not sure about that, I'd have to go look at the kart to be sure, but I think that's how it works.

There's some discussion of it here:
http://www.gokartsupply.com/tcterms.htm

Does that answer the question?

Or were you trying to ask about the free-wheeling wheel rather than the driven wheel?

If so, The hub of the free wheel is simply not keyed, and the nylock nut holding the hub on the axle is simply not tightened all the way down, and axle grease is used between the axle and hub. Normally the axle and free wheeling wheel will be turning at about the same rate, except while going around corners, and normally the relative speeds between the axle and wheel are not very much.

-- steve



Edited 2 time(s). Last edit at 07/28/2012 11:20AM by smcameron.

Steve,

My question was a little back to front.
But you answered part of it anyway.
Now the question is, what is the difference between the two ends of the axle.

Both ends of the axle would be threaded to hold the end nut. Both end nuts are inside the bike wheel when finished. Correct.
The free wheels runs unpinned on the axle, and as you note the axle and the wheel would be moving at the same rate to no major wear. (unless your stuck in mud)
The fixed or driven end, is pinned or keyed. In your videos i think i can see a key recess in the hub, but also a small hole in the side. We will be looking at making the hubs if we cannot find them in OZ. Have not looked yet.

Do you have a sketch or drawing showing the set out of the rear axle. ie thread end 2in, bearing holder etc. etc.. did you thread your own axle ends and is the inside end of the axle machined down to hold the inside face of the bearings.

I imagine your axle is solid.

Two photos if available would answer this.

David

---

David

1960 MGA 1600 Convertible,
Gold Coast, Australia.

Nope, didn't machine my own axle. Yes, it is a solid axle. It is this part:

http://www.gokartsupply.com/axles.htm

1401-40 36 inch axle, 1 inch diameter.

Hub is this part:
http://www.northerntool.com/shop/tools/product_17806_17806

There are no wheel bearings in the rear of the kart.

The bearings are in the frame rails. (very clever bearings
with a spherical shape on the outside that ride in a kind
of cage allowing them to be oriented in any way, but yet
hold them captive, so that the frame rails don't have to
be parallel, or even precisely positioned.)

The axle has a 1/4th inch keyway, as do the hubs, into
which you slot a section of 1/4th inch axle key stock
(just a section of steel rod with a square cross section
of 1/4th inch)

The hole on the side of the hub is for a set screw (if we're
talking about the same hole on the side.)

The bearings are removed from the rear wheels (actually, one
of my rear wheels has a bearing in it -- but only because I put
one in thinking it would be a front wheel, and then was too lazy
to pop it out. That bearing doesn't actually do anything thouugh,
it's not in contact with the axle, but if you saw it in the video,
I could imagine it might cause some confusion.

Popping out the bearings is a PITA, but not too
bad if you have the right tool (a slide hammer bearing puller --
worth it rather than trying to use a screwdriver and a hammer.)

Hope that answers your question -- I'm still not exactly sure
what your question is, but I'm thinking maybe it's just confusion
caused by my superfluous rear bearing.

-- steve

Steve,

The link to the go-kart page answered a number of questions as it is a complete system. I can see the bearing shoulder machined behind where the bearing sits.
I will do some resaerch as to where to pick these up over here.

David

---

David

1960 MGA 1600 Convertible,
Gold Coast, Australia.

David,

Interesting to see the increase in the cockpit length based Steves comments. Sure will assist in me not making the same mistake. Its funny to note the human size isnt scaled unless only children are allowed to drive the finished kart and that would mean no fun for me.

ChrisK

This makes no sense to me. THERE IS NO REAR WHEEL BEARING. No bearing sits on any shoulder of any rear axle.

The axle rides on bearings inside the frame rails, nowhere near any shoulder. These bearings:

http://www.gokartsupply.com/bearings.htm

See part number 1861

Those are not WHEEL bearings. The rear wheels have a grand total of zero bearings. The bearings are in the frame rails, and the axle rides in the bearings.

Steve,

What i meant was the hub when it bolted on pushes against the shoulder machined into the axle.
I confirm there is NO bearing. Here is a qucik sketch of the components.

David

---

David

1960 MGA 1600 Convertible,
Gold Coast, Australia.

Ah, ok. It seems we're in violent agreement. Sorry about the confusion.

-- steve

Hi Gents,

So as it read it only one wheel rear drives from the engine?? This is keyed to the axle whilst the other is free wheeling to over come the differential effect, would I be right????

Over such a short wheel base would the diff effect be so noticeable when driven??? Anyone tried to drive both wheels???

Gyp

The gittreville guys have a variety of drive systems in use:

http://gittrevillegp.com/www.gittrevillegp.com/Blog/Entries/2011/1/19_BUILD_SERIES_no._2__Rear_axle_and_drive.html

-- steve

It's not the drive system so much as single or twin wheel drive, my toylander series 1 landrover I built has twin rear chain drive thus no wheel spins or loss of traction over rough ground.

http://www.toylander.com/Customers_cars.php


I will use one fixed wheel then sort out a diff system if required

Many thanks for the link very useful

Gyp