Author Topic: HMV Freeway  (Read 14544 times)

mharrell

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Re: HMV Freeway
« Reply #15 on: July 02, 2010, 12:44:22 AM »
Better to be prepared for what you are likely to encounter than surprised by it.

You're quite right, of course, and in all seriousness I do appreciate the details you've provided.  I picked it up with an eye towards commuting on city streets, so I'll approach its limits with caution.
197? Lyman Electric Quad (two), 1978 KV Mini 1, 1980 KV Mini 1, 1981 HMV Freeway

Big Al

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Re: HMV Freeway
« Reply #16 on: July 02, 2010, 08:50:27 AM »
On the comments of handling of the Freeway. How disappointing as it looks like a capable car. I could have happily owned one to drive where as most things American like King Midget do nothing for me really.
The handling sounds as compromised as the Tri Tech Schmitt. The reasons are different but related to a design disregarding the known ideals for camber, castor and akeman angles and progressive suspension. The only answer in both cases seems to be as radical as to remove some of the original parts. I do not know the history of Freeway but Tri Tech were copying a vehicle that handles pretty well with the parts coming available new to replicate the original suspension so there is little excuse for their poor design. It did for them in the end as the car in standard form is undrivable above about 45 mph. Several turned over on straight level roads resulting in police confiscationg one vehicle as evidence. I have had three rolled cars and a burned out one myself, broke two and two passed on plus I modded one bought from Andy Carter that is OK up to 55 mph but while I could get it even better I would begin to be concerned about the basic strength of the altered Tri Tech components.
Very frustrating to have a beautiful looking car, on paper with power to be usable but in reality as skitty as a bit of feather in a breeze.
For the Tri Tech it would now be possible to offer a new front suspension kit but fitting would be a major job requiring a front strip down and it would mean replacing the front crossmember to mount Schmitt suspension and a reworked front hydraulic braked hub assembly. Not cheap but the car would then perform up to the limit of the CN250 engine fitted. I cannot see this being successfull as you could buy a KR200 for the outlay unless you picked up the Tri Tech cheap. Indeed it would be cheaper to get the KR200 and put a CN250 in it. Better still now that most panels are available you can build a 'new' KR200 and put a CN250 in it.
My guess none of that is an option on the Freeway. Pity, nice little car.
Messerschmitt set, Goggo Darts, Heinkel 175, Fiat Jolly, Autobianchi, Fairthorpe Electron Minor, Borgward, Isuzu Trooper
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For sale - Vellam Isetta, Bamby, AC Type 70, Velorex, Church Pod, Reliant Mk5, KR200,  Saab 96, Bellemy Trials, Citroen BXs

marcus

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Re: HMV Freeway
« Reply #17 on: July 02, 2010, 09:08:59 AM »
I agree Alan, the Freeway does look better than many US micros/unusuals, shame it is flawed.
Just remember: as one door closes behind you, another slams in your face

AndrewG

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Re: HMV Freeway
« Reply #18 on: July 02, 2010, 01:04:52 PM »
I find the Freeway a fascinating vehicle as it was very cleverly designed (by pukka automotive engineers, I believe) to be economical to produce in relatively small numbers.  This sort of real engineering ("an engineer builds for sixpence what any fool could make for half a crown") is a delight to me and is also useful for considering how a new microcar could be designed.  So I have been a lurker on Freeway forums for a long time.

It does seem that the designers got the front suspension geometry wrong - it may be that they thought it was a relatively slow vehicle and so they didn't need to be all that accurate.  Contrary to Stephen's description of the problem, most Freeway owners who have carried out a simple steering axis modification seem to be happy with the result.  This involves moving the bottom suspension pivot so that it is nearer the wheel centreline, dramatically reducing the positive steering offset - and we have to remember that in those pre-ABS days, all automotive engineers knew that the negative steering offset that is routinely used nowadays not only gave poor steering feel, but would be undriveable.

This is the original suspension and the steering axis (from the top of the McPherson-ish strut) can be seen to hit the ground completely inside the tyre:



Adding a bracket to relocate the bottom joint under the drum gives this:



And this is a good general view of the front end:



I should stress that not only do I not have any personal experience of Freeways, I've never even seen one 'in the flesh' - these are just repeats of other peoples' comments (and photos).

However I will add that Ackermann steering is often seen as ideal, but I don't think any designer would use pure Ackermann nowadays - it was Colin Chapman who actually used reverse Ackermann (inside wheel turns less angle than outside wheel) to compensate for the lower tyre slip angles on the more heavily-loaded outside wheel.

Andrew

steven mandell

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Re: HMV Freeway
« Reply #19 on: July 03, 2010, 12:47:45 PM »
Thank you for your contribution to offsetting (vs. correcting) one of the Freeway's many significant design flaws.
However if I am interpreting  your words correctly this modification towards negative offset steering axis should have the effects of reducing "steering feel", and increasing "undriveability".  So what other effect is being engendered that creates the perception/ possibly even the gestalt of a better steering vehicle?

I'm not saying that it couldn't happen.  With an original design as far off from geometrical ideals as the Freeway has- maybe two wrongs could seem to have the effect of make a more right.  But I am genuinely curious as to exactly what is going on to create this perception.

I also notice that this modification has had the unfortunate effect of raising the front end by what looks like to be at least a couple of inches.  I have modified mine to be a couple inches lower in the front instead by fitting 10 inch wheels instead of 12's in the front, as there was already too much ground clearance.  Lowering the c.g. on this  vehicle's only roll resisting "axle line" is obviously a good way to go to reduce the inherently greater risk of overturning that a 3 wheeled vehicle can present.  It also keeps the lower trailing arm much more parallel to the road surface thus allowing for far less effect of changing the instantaneous effective wheelbase while traversing bumps. With the more ideal design parameters that I have been able to achieve (without sacrificing the novelty of the designer's mesterpiece) and even with your suggested modification- keeping the trailing arm on the level should limit any further untoward influences on an already overly challenged set of geometries.  The shorter the effective trailing arm length (by way of not being in the wholly horizontal orientation)- the greater the change in incurred angularities while progressing through its working arc of travel.
It is also better from the point of aerodynamics in that it both reduces lift and drag by allowing less air under the car at speed, and even probably adds some down force as the front fenders now become more like downward pointing vs more upward pointing wings.  If one intends to drive the Freeway on the freeway at freeway speeds, this should become a significant consideration.

AndrewG

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Re: HMV Freeway
« Reply #20 on: July 03, 2010, 03:13:40 PM »
The owners who've done this small modification think it cures the Freeway handling issues - the Freeway Yahoo group http://autos.groups.yahoo.com/group/freewayhmv/ would be the place to ask them if this is correct.

Andrew