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John Lewis
09-13-2010, 08:04 AM
Here is the year three parts gone and I've built nothing. I think it's time to clean out the shed and get cracking. Mind you Sir J's bus is neat compared with my shed.

Anyway I have purchased the Tomahawk plans and now need to study the possibilities. I'm tempted to use round tube because I still have the Bentech jigs and they are for round tube and will fit the Tomahawk shape nicely. Then again square tube is a bit easier. I had in mind to bend the tube to shape. One piece, no welds. Then only the chainstays and head tube would be welded on. Chainstays as for the Bentech. One inch tube and very strong. I've already proved them over several thousand KM.

Then I began thinking about front wheel drive. How do-able would it be? The problem would be to build a purpose made front fork. I'm looking at the Performer Lowracer as a comparison. If I go rear wheel drive I'd want to drop the chain . Another set of problems but the Lowracer guys here all do that and claim it is much smoother. Of course you do restrict the turning circle.

Then there is the problem of short legs. It will be very tight and I'm sure to need to raise the pedal boom to fit. That isn't all bad as it gets it more in line with the body and hence less drag. I'm led to believe that up to a foot above the seat line is OK. Of course I'd prefer less. Our commercial trikes are about 6" above the seat level.

All said and done perhaps I should just follow the plans. Main reason to build a Tomahawk is better transportability. My Marauder is really great but it really is impossible for me to transport and so is limited to local rides. Tomahawk is more the size of a standard bike and would be allowed on the Railway bus.

So what do you all think? Round tube or square? Front wheel drive? I do have enough square tube left over from the Marauder and most everything else I need. Probably share the wheels with the Marauder to save some cost initially. Good idea or no?

There you go you lot. Now you can all start confusing me with good advise. :jester::jester:

John Lewis

Odd Man Out
09-13-2010, 09:05 AM
My vote: round tube and FWD. I am looking at round tube RWD myself along the lines of the Jester, M5 or Baron models. My thoughts for a successful build head your way.

Wingman
09-13-2010, 09:39 AM
John,

Would you be using Chro-MO round or standard steel (exhaust pipe)? I'd be interested to see how round would turn out especially in the weight department. I second the notion of having a smaller ride that will transport easier. The T-Hawk should work well in that department.

Here's a site you may not have seen-the fellow built a pretty cool FWD Carbon Lowracer. Maybe it will give you some ideas: http://www.jjscozzi.com/

Wingman

SirJoey
09-13-2010, 06:19 PM
Mind you Sir J's bus is neat compared with my shed.
All I can say is :eek:


The **** Is My Shepherd!
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John Lewis
09-15-2010, 07:01 AM
Thanks for the replies chaps,

Sir Joey, I'm not game to post a picture as it would probably be a health hazard. Nah, If I can get the camera in the door I'll do it on the Shop thread.

OMO, Yes I like round tube. I've built a few bikes with it and its not all that much more difficult. There may also be a slight saving in weight. As for stiffness I don't know.
My only problem with front wheel drive is how to fabricate an adequate fork. I think 25Hz may have something on his site so I must go look.

Wingman, I will use muffler tube because it is much cheaper than CroMo. I've built two SWB's from it and a trike. The owner of one of the SWB's has used it for a number of years to commute to work and mine has around 8000km on it so it is more than adequate. A weight penalty for sure but My wallet would be much lighter if I used CroMo.

I had seen the carbon bike you pointed me at. I like the thought of carbon but not the sticky mess I'd get myself into.

At present I think I'll tack up the frame in scrap square tube to work out the dimensions to fit and the get the round tube bent to match. I like the idea of curves. The trouble is that the muffler shop bender tends to shrink the tube a bit but taht shouldn't matter . Perhaps I could use round and just Weld it together in the same manner as the square. I'm still not sure so the first attempt mah be all square.

John Lewis

dynodon
09-16-2010, 08:17 PM
John how much more would it cost to opt for the cromo?

John Lewis
09-17-2010, 09:09 AM
Hi dynodon,

The muffler tube for my Bentech cost less than $20.

CroMo would have been in excess of $100 in this part of the world.

John Lewis

dynodon
09-18-2010, 02:18 PM
anyone know the weight savings between the two types of steel?

MarcusPHagen
09-19-2010, 03:10 AM
anyone know the weight savings between the two types of steel?

The difference in weight between the SUN EZ-tad trikes in mild steel (SX) vs. chromoly (CX) is two pounds. Not sure how much of that difference is the frame, but I'd guess most of it.

Marcus

PS: Googling "weight difference" "mild steel" "chromoly"

produced a concensus that the difference in weight is that chromoly is stronger, which allows for same sized tubes to be thinner (thus saving weight). One figure used was 1/2 thickness, for 1" tubes used in a vehicle roll cage, compared to the same strength in mild steel tubing of the same O.D.

John Lewis
09-20-2010, 11:14 PM
Yes Marcus has it about right. The ChroMo is stronger and you save by using a thinner wall. For examle the muffler tube is about 63 thou. You could use 48 thou or perhaps 30 thou Chro Mo and get a weight saving. The problem comes when you try to weld it. Really needs TIG and then heating to red heat and allowing to cool slowly out of drafts. Or can be brazed.

What would you save. Our LoGo trikes are ChroMo and weigh 20kg. The trike I made from muffler tube weighed 20kg. THe Logo at that point had mudguards, disk brakes and an Sram dualdrive. My guess is that the extra weight if those items would be at most 2 kg. So on the average trike a saving of perhaps 4lbs.

On a low or high racer with just a metre or so long tube the real savings would be less as most of the weight is in thee componentry.

John Lewis

dynodon
09-22-2010, 05:08 PM
sounds like for home building we should stay with mild steel....

John Lewis
09-23-2010, 05:18 AM
Ah, but think of the bragging rights on the cafe strip.:jester:
Seriously though I think for most of our bikes it would be overkill.

I wouldn't mind trying carbon fibre but again I think the benefits would be doubtful for anything I built. Perhaps a carbon seat Maybe Graucho could work out how to airbbrus a wooden seat to look like carbon.:)

John Lewis

schu777
09-23-2010, 07:43 AM
Maybe Graucho could work out how to airbbrus a wooden seat to look like carbon.:)


I saw on American Choppers where they did a snake skin look on a tank - used woman's hose that had the diamond pattern...look like a snake skin - maybe that would work for the "look" of carbon fiber?

John Lewis
10-16-2010, 07:02 AM
Well I've been perusing my plans and getting ideas on what I want to do.
I'm looking at trying to get the geometry sizes similar to a VK2.
To that end do you think there is a problem in using a 24 spoke double wall 622x14 rear wheel. Thats a road bike wheel. 24 spokes is my main worry. One lowracer I saw had 18 spoke wheels though.

Second query is the height of the seat, the bottom bracket and the wheelbase.

As a comparison: The VK2 seat height is 34cm and the Performer 36 cm. The wheel base of the VK2 is 130 cm and the Performer 128 cm. The Bottom Bracket on the performer is 59 cm from ground and the others look similar. The seat angles are all around the 17 to 20 degree mark.

Perhaps some one who has completed could give some figures. By pm is fine if you don't wish to post them for obvious reasons. My guesstimate from the plans is seat about 36 to 38 cm and wheelbase around 130 -140.

I've been trying to superimpose a Tomahawk picture on a VK2 but I'm still trying to puzzle out how to do it with GIMP or Photoshop..

John Lewis

SirJoey
10-16-2010, 09:59 AM
I've been trying to superimpose a Tomahawk picture on a VK2 but I'm still trying to puzzle out how to do it with GIMP or Photoshop.In photoshop, select the top layer in your layers palette, & adjust the opacity.
Hope that helps. :)



***** The **** Is My Shepherd! *****
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-(Geezer & Bent Enthusiast At Large)-

John Lewis
10-17-2010, 03:01 AM
[QUOTE=SirJoey;45452]In photoshop, select the top layer in your layers palette, & adjust the opacity.
Hope that helps. :)

Thanks Sir J,
I knew It had to involve layers. I think I went about it wrongly. I created a new layer and then tried to add my photo to it. I will have to do some reading I guess. Should be plenty on the net.

Of course the other ting I'll need to do is to scale both images to close to the same size.

Found a nice piece of tubing left over from the Marauder so it looks like this first one is going to be in square. I was wanting to use round but I'll use what I have.

John Lewis

John Lewis
10-18-2010, 03:50 AM
Well thanks Sir J,
Your suggestion did the trick and I was able to make the comparison with VK2.
The VK2 uses a 700c type rear wheel so I did several images where I made the front wheel, then the rear wheel the same size. Interestingly the geometry of the Tomahawk is pretty similar top the VK2. Much the same head angle and seat angle. The big difference , and it was not a lot, was the pedal height.

Here are some images.This shows the front wheels same size
http://i254.photobucket.com/albums/hh98/lew2au/Tomahawk/tom1.jpg

Here I've scaled the rear wheel to same size.
http://i254.photobucket.com/albums/hh98/lew2au/Tomahawk/tom3.jpg

This is a straight comparison.
http://i254.photobucket.com/albums/hh98/lew2au/Tomahawk/tom2.jpg


This is looking better and better as a build. I hope it rides as nice as a VK2. :)

Now where under all the junk in my shed is the welder?:jester:

John Lewis

SirJoey
10-18-2010, 08:38 AM
Now where under all the junk in my shed is the welder?:jester:Man, I can SO relate to THAT, mate! :)



***** The **** Is My Shepherd! *****
http://img3.imageshack.us/img3/49/signaturehalloween.jpg
-(Geezer & Bent Enthusiast At Large)-