Can/Should the rear control arms be lightened?
- Thread starter etownsley
- Start date
Dan Sarandrea (Phila)
Waitin' On Parts...
Bumping...
...a good question:innocent:
...a good question:innocent:
X1/9Cruiser
True Classic
I think...
personally, the amount of weight savings you would get would be insignificant. They don't weigh that much to begin with and of course cutting into them will reduce their strength and your piece of mind. Just my opinion though...
personally, the amount of weight savings you would get would be insignificant. They don't weigh that much to begin with and of course cutting into them will reduce their strength and your piece of mind. Just my opinion though...
I have to agree...
I have thought about making a different set in the rear with tublar arms, etc, but the weight would end up about the same.
The only thing I can think of to make it lighter would be to replace the whole thing with a cast aluminum piece like what the RX7 suspension is made of. Lots of fabricating and big bucks to do it though.
However, I still find myself looking at it and trying to figure out a better mouse trap.
Eric
I have thought about making a different set in the rear with tublar arms, etc, but the weight would end up about the same.
The only thing I can think of to make it lighter would be to replace the whole thing with a cast aluminum piece like what the RX7 suspension is made of. Lots of fabricating and big bucks to do it though.
However, I still find myself looking at it and trying to figure out a better mouse trap.
Eric
Rupunzell
Bernice Loui
Those stock lower A arms have very good strength to weight ratio, replacing them with tubular ones might not make much of an improvement in un-sprung weight. It does have the possibility of allowing further rear suspension adjust-a-ability via spherical rod ends if tubular replacements are made.
Better to re-do the rear upright in aluminum or properly designed, welded tubular construction. Same applies to the front uprights.
The easiest place reduce un-sprung weight is lower the weight of the wheels and tire combo.
Puleo and the rest of the FIAT / Bertone design staff did their homework well when they designed this chassis.
Better to re-do the rear upright in aluminum or properly designed, welded tubular construction. Same applies to the front uprights.
The easiest place reduce un-sprung weight is lower the weight of the wheels and tire combo.
Puleo and the rest of the FIAT / Bertone design staff did their homework well when they designed this chassis.
Dan Sarandrea (Phila)
Waitin' On Parts...
Theoretical Question
Hi Bernice,
If someone were to simply take an existing upright and duplicate it by casting it in aluminum, would the cast aluminum version have enough strength to give the same service as the original (steel I'm assuming) in non-racing use?
Hi Bernice,
If someone were to simply take an existing upright and duplicate it by casting it in aluminum, would the cast aluminum version have enough strength to give the same service as the original (steel I'm assuming) in non-racing use?
etownsley
Streel Legal GP Race Car
Thanks for the responses.
I happen to agree. I have drilled holes in several other steel parts on my X since posting this question. The pounds just don't come off like you would like to see.
It's a lot of effort to drill holes in order to lighten the part plus make it look good at the same time. Just not worth it for the most part.
One needs the peace of mind in an autocross run that the car is going to hold together. I will leave mine as is.
Do not attempt casting your own! The likelyhood of foreign particles getting into your casting and compromising it's strength is very high. If they are to be made....machine them from billet 6061-T6 aluminum.
Thanks Again!
I happen to agree. I have drilled holes in several other steel parts on my X since posting this question. The pounds just don't come off like you would like to see.
It's a lot of effort to drill holes in order to lighten the part plus make it look good at the same time. Just not worth it for the most part.
One needs the peace of mind in an autocross run that the car is going to hold together. I will leave mine as is.
Do not attempt casting your own! The likelyhood of foreign particles getting into your casting and compromising it's strength is very high. If they are to be made....machine them from billet 6061-T6 aluminum.
Thanks Again!
Black-Tooth
Tony Natoli
Yeah... I believe Bernice hit the mark with...
... "Unsprung" weight.
In this case... if you wanna work on weight savings, it would be best to focus on the "sprung-weight" category, where it should make a noticeable difference.
Good luck with this ride... it really looks exciting!
... "Unsprung" weight.
In this case... if you wanna work on weight savings, it would be best to focus on the "sprung-weight" category, where it should make a noticeable difference.
Good luck with this ride... it really looks exciting!
Rupunzell
Bernice Loui
If done properly using the correct materials this is likely to be OK. Doing this via the old fashioned back yard sand cast method, the casting might be too porous (like Austin Allegro alloy wheels that would not hold air) with hidden casting flaws that could result in part failure. There would also be the casting material question and all the other complexities of doing a proper casting.
Suspension failures are NOT tolerable under any condition.
It's one thing to grenade an engine or gear box, if something fails on the suspension, something really bad usually happens including death of the driver and occupants.
If one were to play serious games, re-design the entire part in magnesium (many race cars have magnesium uprights) complete with revised geometry, proper spherical rod ends and etc. This would be a serious design undertaking similar to a suspension re-design. ala the Dallara X1/9.
Not sure what the OE ones are made of, maybe I'll check at some point.
Suspension failures are NOT tolerable under any condition.
It's one thing to grenade an engine or gear box, if something fails on the suspension, something really bad usually happens including death of the driver and occupants.
If one were to play serious games, re-design the entire part in magnesium (many race cars have magnesium uprights) complete with revised geometry, proper spherical rod ends and etc. This would be a serious design undertaking similar to a suspension re-design. ala the Dallara X1/9.
Not sure what the OE ones are made of, maybe I'll check at some point.
Update....
Well, I happened to be trolling ebay, and ran across this picture from a Fiat 500. Here is an idea to get your rear control arm a bit lighter. See picture #12.
http://cgi.ebay.com/ebaymotors/Fiat...5&_trkparms=72:1205|65:12|39:1|240:1318#v4-46
Eric
Well, I happened to be trolling ebay, and ran across this picture from a Fiat 500. Here is an idea to get your rear control arm a bit lighter. See picture #12.
http://cgi.ebay.com/ebaymotors/Fiat...5&_trkparms=72:1205|65:12|39:1|240:1318#v4-46
Eric
etownsley
Streel Legal GP Race Car
That is what I had in mind.
I was thinking about laying out a series of holes on all three sides of the arms. There would be a stagger on the holes from each adjacent side. Center punch them first followed by a 1/4" drill bit and finished off with a hole saw.
I also considered milling some material(about 1/8") off the open ends of the channels.
I work in a tool & die shop so I have access to all the vises, machines and cutters that I would need. I'm just unsure about how much I might weaken the control arms.
If anyone has done this modification, please comment on how well they have worked. Thanks.
I was thinking about laying out a series of holes on all three sides of the arms. There would be a stagger on the holes from each adjacent side. Center punch them first followed by a 1/4" drill bit and finished off with a hole saw.
I also considered milling some material(about 1/8") off the open ends of the channels.
I work in a tool & die shop so I have access to all the vises, machines and cutters that I would need. I'm just unsure about how much I might weaken the control arms.
If anyone has done this modification, please comment on how well they have worked. Thanks.
xone9
Matt
If your looking to lower unsprung weight
Rupunzell is right.. certain wheel and tire packages weigh considerably more than their motorsport orientated counterparts. I weighed my 13X5.5 inch minilites with 185/60s on them (12.5 kg), with a lighter wheel and road legal race tire i guess that figure could be brought down closer to 8kg?? which is a huge improvment in unsprung weight.
Rupunzell is right.. certain wheel and tire packages weigh considerably more than their motorsport orientated counterparts. I weighed my 13X5.5 inch minilites with 185/60s on them (12.5 kg), with a lighter wheel and road legal race tire i guess that figure could be brought down closer to 8kg?? which is a huge improvment in unsprung weight.
John Allen
True Classic
If you are going to drill a bunch of large diameter holes in the arm, you may want to consider 'flanging' the hole with a die so the material will remain rigid.
In my opinion, too much work for the benefit.
-John
In my opinion, too much work for the benefit.
-John
Rupunzell
Bernice Loui
I don't want to see a "Darwin Award" as a result of this effort to try and "save weight" where it will make little if any difference.
So we drill a bunch'a holes in the rear lower A arm, save the chips and put them on a very accurate scale to see precisely how much weight was saved. I suspect less than expected.
Then we now have a bunch of possible stress risers from the drilled holes which require a proper deburring and flanging to prevent the possibility of fatigue cracking and part failure when least expected, like pulling over 1.5G around a turn at 100+ Mph. The results are not likely going to be pretty. Then it is likely the A arm will not be as rigid as deliverd which will change suspension geometry when loaded. And, the list of problems goes on the more I think about this....
In three words, "Don't Do This".
So we drill a bunch'a holes in the rear lower A arm, save the chips and put them on a very accurate scale to see precisely how much weight was saved. I suspect less than expected.
Then we now have a bunch of possible stress risers from the drilled holes which require a proper deburring and flanging to prevent the possibility of fatigue cracking and part failure when least expected, like pulling over 1.5G around a turn at 100+ Mph. The results are not likely going to be pretty. Then it is likely the A arm will not be as rigid as deliverd which will change suspension geometry when loaded. And, the list of problems goes on the more I think about this....
In three words, "Don't Do This".