Linear Recumbent Specs

[KoffMixtures]

Spent an inordinate amount of time trying to find basic specs for the LWB Linear Recumbent without success.
Can someone please provide the wheelbase and the main frame beam cross section?

 

[FrankCrank]

Looking at it, my guess would be 3" x 2" for the main beam, and being aly i'd say 3 or 4 mm wall. Just a guess.

It looks like it's got a 20" front wheel, so you ought to be able to use that as a reference to determine wheelbase.

I personally wouldn't build a LWB in aly, due to likelihood of fatigue failure. Sold in low numbers - could be a good reason?

 

[a.twiddler]

Linear dimensions.
Just been out to measure mine.
The frame is an “I” beam. It is 3” deep X 1 ½” wide. The top and bottom of the I are 1/8” proud of each side to allow for clamping on of components. The New York built Linears produced by Peter Stull may be different again, though he continued to use up older frame parts, with modifications, in the early 2000s, until he began to produce the re engineered models.

How long is the Linear wheelbase? Iowa Linears came in a range of frame sizes. According to the basic information sheet that came with mine:-

Inseam Measurement Recommended Frame Size
22"-26" = 36"
25"-29" =39"
28"-32" = 42"
31"-35" = 45"
34" & over = 48"

It goes on to say, "The LINEAR is very adjustable and can accommodate a wide range of individual sizes. (For example a person with a 28" inseam can fit on a 45" frame.)
How they worked out the different frame sizes I can only guess. The main beam on mine is just about 42" so it's feasible that that was the part that varied between different frame sizes. That would mean that there was a foot in length difference between the largest and smallest sizes, and maybe a choice of wheel sizes on the smallest ones. I have a photo of what is essentially an Iowa Linear titled “Linear Mach III” which has a welded frame and 20” rear, 16” front, wheels. The frame length will also affect the wheelbase which on mine is 65 1/2”.

Linears are very modifiable, for example the rear wheel for most will be 26", though mine came with a 700c rim built on to the Sachs 3 X 7 hub by the previous owner. It had a drum brake front wheel with a French standard 440 20" rim on it. Probably the original would have been a 451 20" rim, more common in the US, swapped for the sake of the drum brake. I've since swapped that for a 406 20" drum brake wheel, as the tyre choice is better.

Definitely not a "one size fits all" with the Linear. This is irrelevant for most British Linear buyers, as they would all be pretty much pre owned and you would buy whatever became available at the time. But it goes to show that Linear tried to make a tailor made product for their customers buying new. I could have ended up with a 48" frame, while a larger person might have ended up with a smaller frame, depending on how much of the range was imported into the UK in the 80s and 90s.

No doubt the steel vs aluminium debate rages on, but I certainly have no qualms about loading mine up and setting off on trips. It dates from around the mid 90s, I've had it for nearly four years now and have used it a lot, and it inspires faith.

Any other info or measurements needed, please ask.

 

[KoffMixtures]

Thanks for your comments and info, a.twiddler, much appreciated.

Considering how long Linear's have been and are still in production, I don't think the use of the alloy extruded beam is an issue.

As far as I can tell, the only structural weakness was the rear extensions developing cracks; cured by a bracing plate.

The cross section of the spine is now around 1/4'' wider.
Since posting my question, further research indeed confirms your measurements.
My own estimations based on photo's turned out to be amazingly accurate.

It would be helpful to know the fork rake and trail?
Also, is the head tube steel and at at 90degrees to the frame?
Are the head tube and rear drop out sections 'bolted' on?

Is it possible to ride 'hands off'?

Thanks, again.

 

[a.twiddler]

The early Iowa Linears went through a process of gradual improvement as production proceeded. Pre about 1988 the frame width was 1 1/4", post 1988 it was increased to 1 1/2" to improve stiffness when heavily loaded.
One of the modifications made to Iowa pattern Linears when production restarted in New York was the addition of the rear fork reinforcing plate. Some batches also had V brake posts which were able to be attached to these plates. Aftermarket reinforcing plates were available so that owners could update and "futureproof" their Linears.

I don't have the figures for rake and trail at the moment.
The forks are steel, with a 1" threaded steerer in keeping with their vintage.
The head tube is non ferrous, presumably cast aluminium, part of a shaped block which fits into the front part of the frame in line with the angle shown in the picture. The block is retained in the frame by two quick releases. The underside of this part of the frame is open so when the quick releases are opened the block can slide forward and the block, together with the head tube, fork and wheel can pivot down and back under the frame. When unfolding the front wheel, it is important to ensure that the block is fully slid back into the frame before tightening the quick releases.
There is a similar set up at the rear. When the quick releases are opened, the front one can slide forward in a slot, allowing the rear fork and wheel to fold under. The quick releases could be replaced by bolts if there was no need for the fold. To remove the head tube and rear fork, you just remove the quick releases.

As for riding hands off, it's easy enough to ride with light fingertip pressure, but I haven't gone that far. Someone out there will have done it, I'm sure.

 

[KoffMixtures]

a.twidler, thank you for taking the time to kindly respond to my questions.

The rear frame members...are they steel or alloy?

Being much more popular in the US, used recumbents are sensibly priced there; so much so, it would seem uneconomic to go the self built rout, unless something specific is required.

I recon I can build a 'replica' Linear for less than £100 using all new parts (not costing my own time).

 

[a.twiddler]

The Linear rear fork is aluminium.
The Linear isn't the only LWB recumbent to use a beam type frame. Here is a Cresswell Rapide, made in Birmingham in the 1990s. This uses pressed steel, including the front fork.

There are some on this forum who have built their own bikes, mostly tubular steel, I would imagine. There are plans out there, though the classic American LWB geometry is well established since the Avatar 2000 in 1980, whether you use metal, plywood or plastic to connect it all together. It sounds like an interesting project!

 

[a.twiddler]

When I first saw the thread title, "Linear Recumbent Specs", what sprang to mind were these:-

One pair for sunny days, one pair for dull days. They are varifocals but the seat is not so reclined as to cause problems with them. They work fine.